diff --git a/src/csharp/Grpc.Examples/MathGrpc.cs b/src/csharp/Grpc.Examples/MathGrpc.cs
index e29b1087e45a6..045708b947f10 100644
--- a/src/csharp/Grpc.Examples/MathGrpc.cs
+++ b/src/csharp/Grpc.Examples/MathGrpc.cs
@@ -20,9 +20,6 @@
 #pragma warning disable 1591
 #region Designer generated code
 
-using System;
-using System.Threading;
-using System.Threading.Tasks;
 using grpc = global::Grpc.Core;
 
 namespace Math {
@@ -159,7 +156,7 @@ protected MathClient(ClientBaseConfiguration configuration) : base(configuration
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The response received from the server.</returns>
-      public virtual global::Math.DivReply Div(global::Math.DivArgs request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Math.DivReply Div(global::Math.DivArgs request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return Div(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -183,7 +180,7 @@ protected MathClient(ClientBaseConfiguration configuration) : base(configuration
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncUnaryCall<global::Math.DivReply> DivAsync(global::Math.DivArgs request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Math.DivReply> DivAsync(global::Math.DivArgs request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return DivAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -208,7 +205,7 @@ protected MathClient(ClientBaseConfiguration configuration) : base(configuration
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncDuplexStreamingCall<global::Math.DivArgs, global::Math.DivReply> DivMany(grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncDuplexStreamingCall<global::Math.DivArgs, global::Math.DivReply> DivMany(grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return DivMany(new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -234,7 +231,7 @@ protected MathClient(ClientBaseConfiguration configuration) : base(configuration
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncServerStreamingCall<global::Math.Num> Fib(global::Math.FibArgs request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncServerStreamingCall<global::Math.Num> Fib(global::Math.FibArgs request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return Fib(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -258,7 +255,7 @@ protected MathClient(ClientBaseConfiguration configuration) : base(configuration
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncClientStreamingCall<global::Math.Num, global::Math.Num> Sum(grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncClientStreamingCall<global::Math.Num, global::Math.Num> Sum(grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return Sum(new grpc::CallOptions(headers, deadline, cancellationToken));
       }
diff --git a/src/csharp/Grpc.HealthCheck/HealthGrpc.cs b/src/csharp/Grpc.HealthCheck/HealthGrpc.cs
index 24a72599798fa..1d80bcd59ecd1 100644
--- a/src/csharp/Grpc.HealthCheck/HealthGrpc.cs
+++ b/src/csharp/Grpc.HealthCheck/HealthGrpc.cs
@@ -20,9 +20,6 @@
 #pragma warning disable 1591
 #region Designer generated code
 
-using System;
-using System.Threading;
-using System.Threading.Tasks;
 using grpc = global::Grpc.Core;
 
 namespace Grpc.Health.V1 {
@@ -79,7 +76,7 @@ protected HealthClient(ClientBaseConfiguration configuration) : base(configurati
       {
       }
 
-      public virtual global::Grpc.Health.V1.HealthCheckResponse Check(global::Grpc.Health.V1.HealthCheckRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Health.V1.HealthCheckResponse Check(global::Grpc.Health.V1.HealthCheckRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return Check(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -87,7 +84,7 @@ protected HealthClient(ClientBaseConfiguration configuration) : base(configurati
       {
         return CallInvoker.BlockingUnaryCall(__Method_Check, null, options, request);
       }
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Health.V1.HealthCheckResponse> CheckAsync(global::Grpc.Health.V1.HealthCheckRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Health.V1.HealthCheckResponse> CheckAsync(global::Grpc.Health.V1.HealthCheckRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return CheckAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
diff --git a/src/csharp/Grpc.IntegrationTesting/Control.cs b/src/csharp/Grpc.IntegrationTesting/Control.cs
index 8e5da7b9f2188..879572890682e 100644
--- a/src/csharp/Grpc.IntegrationTesting/Control.cs
+++ b/src/csharp/Grpc.IntegrationTesting/Control.cs
@@ -32,7 +32,7 @@ static ControlReflection() {
             "U2VjdXJpdHlQYXJhbXMSEwoLdXNlX3Rlc3RfY2EYASABKAgSHAoUc2VydmVy",
             "X2hvc3Rfb3ZlcnJpZGUYAiABKAkSEQoJY3JlZF90eXBlGAMgASgJIk0KCkNo",
             "YW5uZWxBcmcSDAoEbmFtZRgBIAEoCRITCglzdHJfdmFsdWUYAiABKAlIABIT",
-            "CglpbnRfdmFsdWUYAyABKAVIAEIHCgV2YWx1ZSLVBAoMQ2xpZW50Q29uZmln",
+            "CglpbnRfdmFsdWUYAyABKAVIAEIHCgV2YWx1ZSLvBAoMQ2xpZW50Q29uZmln",
             "EhYKDnNlcnZlcl90YXJnZXRzGAEgAygJEi0KC2NsaWVudF90eXBlGAIgASgO",
             "MhguZ3JwYy50ZXN0aW5nLkNsaWVudFR5cGUSNQoPc2VjdXJpdHlfcGFyYW1z",
             "GAMgASgLMhwuZ3JwYy50ZXN0aW5nLlNlY3VyaXR5UGFyYW1zEiQKHG91dHN0",
@@ -45,59 +45,60 @@ static ControlReflection() {
             "dG9ncmFtUGFyYW1zEhEKCWNvcmVfbGlzdBgNIAMoBRISCgpjb3JlX2xpbWl0",
             "GA4gASgFEhgKEG90aGVyX2NsaWVudF9hcGkYDyABKAkSLgoMY2hhbm5lbF9h",
             "cmdzGBAgAygLMhguZ3JwYy50ZXN0aW5nLkNoYW5uZWxBcmcSFgoOdGhyZWFk",
-            "c19wZXJfY3EYESABKAUSGwoTbWVzc2FnZXNfcGVyX3N0cmVhbRgSIAEoBSI4",
-            "CgxDbGllbnRTdGF0dXMSKAoFc3RhdHMYASABKAsyGS5ncnBjLnRlc3Rpbmcu",
-            "Q2xpZW50U3RhdHMiFQoETWFyaxINCgVyZXNldBgBIAEoCCJoCgpDbGllbnRB",
-            "cmdzEisKBXNldHVwGAEgASgLMhouZ3JwYy50ZXN0aW5nLkNsaWVudENvbmZp",
-            "Z0gAEiIKBG1hcmsYAiABKAsyEi5ncnBjLnRlc3RpbmcuTWFya0gAQgkKB2Fy",
-            "Z3R5cGUi/QIKDFNlcnZlckNvbmZpZxItCgtzZXJ2ZXJfdHlwZRgBIAEoDjIY",
-            "LmdycGMudGVzdGluZy5TZXJ2ZXJUeXBlEjUKD3NlY3VyaXR5X3BhcmFtcxgC",
-            "IAEoCzIcLmdycGMudGVzdGluZy5TZWN1cml0eVBhcmFtcxIMCgRwb3J0GAQg",
-            "ASgFEhwKFGFzeW5jX3NlcnZlcl90aHJlYWRzGAcgASgFEhIKCmNvcmVfbGlt",
-            "aXQYCCABKAUSMwoOcGF5bG9hZF9jb25maWcYCSABKAsyGy5ncnBjLnRlc3Rp",
-            "bmcuUGF5bG9hZENvbmZpZxIRCgljb3JlX2xpc3QYCiADKAUSGAoQb3RoZXJf",
-            "c2VydmVyX2FwaRgLIAEoCRIWCg50aHJlYWRzX3Blcl9jcRgMIAEoBRIcChNy",
-            "ZXNvdXJjZV9xdW90YV9zaXplGOkHIAEoBRIvCgxjaGFubmVsX2FyZ3MY6gcg",
-            "AygLMhguZ3JwYy50ZXN0aW5nLkNoYW5uZWxBcmciaAoKU2VydmVyQXJncxIr",
-            "CgVzZXR1cBgBIAEoCzIaLmdycGMudGVzdGluZy5TZXJ2ZXJDb25maWdIABIi",
-            "CgRtYXJrGAIgASgLMhIuZ3JwYy50ZXN0aW5nLk1hcmtIAEIJCgdhcmd0eXBl",
-            "IlUKDFNlcnZlclN0YXR1cxIoCgVzdGF0cxgBIAEoCzIZLmdycGMudGVzdGlu",
-            "Zy5TZXJ2ZXJTdGF0cxIMCgRwb3J0GAIgASgFEg0KBWNvcmVzGAMgASgFIg0K",
-            "C0NvcmVSZXF1ZXN0Ih0KDENvcmVSZXNwb25zZRINCgVjb3JlcxgBIAEoBSIG",
-            "CgRWb2lkIv0BCghTY2VuYXJpbxIMCgRuYW1lGAEgASgJEjEKDWNsaWVudF9j",
-            "b25maWcYAiABKAsyGi5ncnBjLnRlc3RpbmcuQ2xpZW50Q29uZmlnEhMKC251",
-            "bV9jbGllbnRzGAMgASgFEjEKDXNlcnZlcl9jb25maWcYBCABKAsyGi5ncnBj",
-            "LnRlc3RpbmcuU2VydmVyQ29uZmlnEhMKC251bV9zZXJ2ZXJzGAUgASgFEhYK",
-            "Dndhcm11cF9zZWNvbmRzGAYgASgFEhkKEWJlbmNobWFya19zZWNvbmRzGAcg",
-            "ASgFEiAKGHNwYXduX2xvY2FsX3dvcmtlcl9jb3VudBgIIAEoBSI2CglTY2Vu",
-            "YXJpb3MSKQoJc2NlbmFyaW9zGAEgAygLMhYuZ3JwYy50ZXN0aW5nLlNjZW5h",
-            "cmlvIoQEChVTY2VuYXJpb1Jlc3VsdFN1bW1hcnkSCwoDcXBzGAEgASgBEhsK",
-            "E3Fwc19wZXJfc2VydmVyX2NvcmUYAiABKAESGgoSc2VydmVyX3N5c3RlbV90",
-            "aW1lGAMgASgBEhgKEHNlcnZlcl91c2VyX3RpbWUYBCABKAESGgoSY2xpZW50",
-            "X3N5c3RlbV90aW1lGAUgASgBEhgKEGNsaWVudF91c2VyX3RpbWUYBiABKAES",
-            "EgoKbGF0ZW5jeV81MBgHIAEoARISCgpsYXRlbmN5XzkwGAggASgBEhIKCmxh",
-            "dGVuY3lfOTUYCSABKAESEgoKbGF0ZW5jeV85ORgKIAEoARITCgtsYXRlbmN5",
-            "Xzk5ORgLIAEoARIYChBzZXJ2ZXJfY3B1X3VzYWdlGAwgASgBEiYKHnN1Y2Nl",
-            "c3NmdWxfcmVxdWVzdHNfcGVyX3NlY29uZBgNIAEoARIiChpmYWlsZWRfcmVx",
-            "dWVzdHNfcGVyX3NlY29uZBgOIAEoARIgChhjbGllbnRfcG9sbHNfcGVyX3Jl",
-            "cXVlc3QYDyABKAESIAoYc2VydmVyX3BvbGxzX3Blcl9yZXF1ZXN0GBAgASgB",
-            "EiIKGnNlcnZlcl9xdWVyaWVzX3Blcl9jcHVfc2VjGBEgASgBEiIKGmNsaWVu",
-            "dF9xdWVyaWVzX3Blcl9jcHVfc2VjGBIgASgBIoMDCg5TY2VuYXJpb1Jlc3Vs",
-            "dBIoCghzY2VuYXJpbxgBIAEoCzIWLmdycGMudGVzdGluZy5TY2VuYXJpbxIu",
-            "CglsYXRlbmNpZXMYAiABKAsyGy5ncnBjLnRlc3RpbmcuSGlzdG9ncmFtRGF0",
-            "YRIvCgxjbGllbnRfc3RhdHMYAyADKAsyGS5ncnBjLnRlc3RpbmcuQ2xpZW50",
-            "U3RhdHMSLwoMc2VydmVyX3N0YXRzGAQgAygLMhkuZ3JwYy50ZXN0aW5nLlNl",
-            "cnZlclN0YXRzEhQKDHNlcnZlcl9jb3JlcxgFIAMoBRI0CgdzdW1tYXJ5GAYg",
-            "ASgLMiMuZ3JwYy50ZXN0aW5nLlNjZW5hcmlvUmVzdWx0U3VtbWFyeRIWCg5j",
-            "bGllbnRfc3VjY2VzcxgHIAMoCBIWCg5zZXJ2ZXJfc3VjY2VzcxgIIAMoCBI5",
-            "Cg9yZXF1ZXN0X3Jlc3VsdHMYCSADKAsyIC5ncnBjLnRlc3RpbmcuUmVxdWVz",
-            "dFJlc3VsdENvdW50KkEKCkNsaWVudFR5cGUSDwoLU1lOQ19DTElFTlQQABIQ",
-            "CgxBU1lOQ19DTElFTlQQARIQCgxPVEhFUl9DTElFTlQQAipbCgpTZXJ2ZXJU",
-            "eXBlEg8KC1NZTkNfU0VSVkVSEAASEAoMQVNZTkNfU0VSVkVSEAESGAoUQVNZ",
-            "TkNfR0VORVJJQ19TRVJWRVIQAhIQCgxPVEhFUl9TRVJWRVIQAypyCgdScGNU",
-            "eXBlEgkKBVVOQVJZEAASDQoJU1RSRUFNSU5HEAESGQoVU1RSRUFNSU5HX0ZS",
-            "T01fQ0xJRU5UEAISGQoVU1RSRUFNSU5HX0ZST01fU0VSVkVSEAMSFwoTU1RS",
-            "RUFNSU5HX0JPVEhfV0FZUxAEYgZwcm90bzM="));
+            "c19wZXJfY3EYESABKAUSGwoTbWVzc2FnZXNfcGVyX3N0cmVhbRgSIAEoBRIY",
+            "ChB1c2VfY29hbGVzY2VfYXBpGBMgASgIIjgKDENsaWVudFN0YXR1cxIoCgVz",
+            "dGF0cxgBIAEoCzIZLmdycGMudGVzdGluZy5DbGllbnRTdGF0cyIVCgRNYXJr",
+            "Eg0KBXJlc2V0GAEgASgIImgKCkNsaWVudEFyZ3MSKwoFc2V0dXAYASABKAsy",
+            "Gi5ncnBjLnRlc3RpbmcuQ2xpZW50Q29uZmlnSAASIgoEbWFyaxgCIAEoCzIS",
+            "LmdycGMudGVzdGluZy5NYXJrSABCCQoHYXJndHlwZSL9AgoMU2VydmVyQ29u",
+            "ZmlnEi0KC3NlcnZlcl90eXBlGAEgASgOMhguZ3JwYy50ZXN0aW5nLlNlcnZl",
+            "clR5cGUSNQoPc2VjdXJpdHlfcGFyYW1zGAIgASgLMhwuZ3JwYy50ZXN0aW5n",
+            "LlNlY3VyaXR5UGFyYW1zEgwKBHBvcnQYBCABKAUSHAoUYXN5bmNfc2VydmVy",
+            "X3RocmVhZHMYByABKAUSEgoKY29yZV9saW1pdBgIIAEoBRIzCg5wYXlsb2Fk",
+            "X2NvbmZpZxgJIAEoCzIbLmdycGMudGVzdGluZy5QYXlsb2FkQ29uZmlnEhEK",
+            "CWNvcmVfbGlzdBgKIAMoBRIYChBvdGhlcl9zZXJ2ZXJfYXBpGAsgASgJEhYK",
+            "DnRocmVhZHNfcGVyX2NxGAwgASgFEhwKE3Jlc291cmNlX3F1b3RhX3NpemUY",
+            "6QcgASgFEi8KDGNoYW5uZWxfYXJncxjqByADKAsyGC5ncnBjLnRlc3Rpbmcu",
+            "Q2hhbm5lbEFyZyJoCgpTZXJ2ZXJBcmdzEisKBXNldHVwGAEgASgLMhouZ3Jw",
+            "Yy50ZXN0aW5nLlNlcnZlckNvbmZpZ0gAEiIKBG1hcmsYAiABKAsyEi5ncnBj",
+            "LnRlc3RpbmcuTWFya0gAQgkKB2FyZ3R5cGUiVQoMU2VydmVyU3RhdHVzEigK",
+            "BXN0YXRzGAEgASgLMhkuZ3JwYy50ZXN0aW5nLlNlcnZlclN0YXRzEgwKBHBv",
+            "cnQYAiABKAUSDQoFY29yZXMYAyABKAUiDQoLQ29yZVJlcXVlc3QiHQoMQ29y",
+            "ZVJlc3BvbnNlEg0KBWNvcmVzGAEgASgFIgYKBFZvaWQi/QEKCFNjZW5hcmlv",
+            "EgwKBG5hbWUYASABKAkSMQoNY2xpZW50X2NvbmZpZxgCIAEoCzIaLmdycGMu",
+            "dGVzdGluZy5DbGllbnRDb25maWcSEwoLbnVtX2NsaWVudHMYAyABKAUSMQoN",
+            "c2VydmVyX2NvbmZpZxgEIAEoCzIaLmdycGMudGVzdGluZy5TZXJ2ZXJDb25m",
+            "aWcSEwoLbnVtX3NlcnZlcnMYBSABKAUSFgoOd2FybXVwX3NlY29uZHMYBiAB",
+            "KAUSGQoRYmVuY2htYXJrX3NlY29uZHMYByABKAUSIAoYc3Bhd25fbG9jYWxf",
+            "d29ya2VyX2NvdW50GAggASgFIjYKCVNjZW5hcmlvcxIpCglzY2VuYXJpb3MY",
+            "ASADKAsyFi5ncnBjLnRlc3RpbmcuU2NlbmFyaW8ihAQKFVNjZW5hcmlvUmVz",
+            "dWx0U3VtbWFyeRILCgNxcHMYASABKAESGwoTcXBzX3Blcl9zZXJ2ZXJfY29y",
+            "ZRgCIAEoARIaChJzZXJ2ZXJfc3lzdGVtX3RpbWUYAyABKAESGAoQc2VydmVy",
+            "X3VzZXJfdGltZRgEIAEoARIaChJjbGllbnRfc3lzdGVtX3RpbWUYBSABKAES",
+            "GAoQY2xpZW50X3VzZXJfdGltZRgGIAEoARISCgpsYXRlbmN5XzUwGAcgASgB",
+            "EhIKCmxhdGVuY3lfOTAYCCABKAESEgoKbGF0ZW5jeV85NRgJIAEoARISCgps",
+            "YXRlbmN5Xzk5GAogASgBEhMKC2xhdGVuY3lfOTk5GAsgASgBEhgKEHNlcnZl",
+            "cl9jcHVfdXNhZ2UYDCABKAESJgoec3VjY2Vzc2Z1bF9yZXF1ZXN0c19wZXJf",
+            "c2Vjb25kGA0gASgBEiIKGmZhaWxlZF9yZXF1ZXN0c19wZXJfc2Vjb25kGA4g",
+            "ASgBEiAKGGNsaWVudF9wb2xsc19wZXJfcmVxdWVzdBgPIAEoARIgChhzZXJ2",
+            "ZXJfcG9sbHNfcGVyX3JlcXVlc3QYECABKAESIgoac2VydmVyX3F1ZXJpZXNf",
+            "cGVyX2NwdV9zZWMYESABKAESIgoaY2xpZW50X3F1ZXJpZXNfcGVyX2NwdV9z",
+            "ZWMYEiABKAEigwMKDlNjZW5hcmlvUmVzdWx0EigKCHNjZW5hcmlvGAEgASgL",
+            "MhYuZ3JwYy50ZXN0aW5nLlNjZW5hcmlvEi4KCWxhdGVuY2llcxgCIAEoCzIb",
+            "LmdycGMudGVzdGluZy5IaXN0b2dyYW1EYXRhEi8KDGNsaWVudF9zdGF0cxgD",
+            "IAMoCzIZLmdycGMudGVzdGluZy5DbGllbnRTdGF0cxIvCgxzZXJ2ZXJfc3Rh",
+            "dHMYBCADKAsyGS5ncnBjLnRlc3RpbmcuU2VydmVyU3RhdHMSFAoMc2VydmVy",
+            "X2NvcmVzGAUgAygFEjQKB3N1bW1hcnkYBiABKAsyIy5ncnBjLnRlc3Rpbmcu",
+            "U2NlbmFyaW9SZXN1bHRTdW1tYXJ5EhYKDmNsaWVudF9zdWNjZXNzGAcgAygI",
+            "EhYKDnNlcnZlcl9zdWNjZXNzGAggAygIEjkKD3JlcXVlc3RfcmVzdWx0cxgJ",
+            "IAMoCzIgLmdycGMudGVzdGluZy5SZXF1ZXN0UmVzdWx0Q291bnQqQQoKQ2xp",
+            "ZW50VHlwZRIPCgtTWU5DX0NMSUVOVBAAEhAKDEFTWU5DX0NMSUVOVBABEhAK",
+            "DE9USEVSX0NMSUVOVBACKlsKClNlcnZlclR5cGUSDwoLU1lOQ19TRVJWRVIQ",
+            "ABIQCgxBU1lOQ19TRVJWRVIQARIYChRBU1lOQ19HRU5FUklDX1NFUlZFUhAC",
+            "EhAKDE9USEVSX1NFUlZFUhADKnIKB1JwY1R5cGUSCQoFVU5BUlkQABINCglT",
+            "VFJFQU1JTkcQARIZChVTVFJFQU1JTkdfRlJPTV9DTElFTlQQAhIZChVTVFJF",
+            "QU1JTkdfRlJPTV9TRVJWRVIQAxIXChNTVFJFQU1JTkdfQk9USF9XQVlTEARi",
+            "BnByb3RvMw=="));
       descriptor = pbr::FileDescriptor.FromGeneratedCode(descriptorData,
           new pbr::FileDescriptor[] { global::Grpc.Testing.PayloadsReflection.Descriptor, global::Grpc.Testing.StatsReflection.Descriptor, },
           new pbr::GeneratedClrTypeInfo(new[] {typeof(global::Grpc.Testing.ClientType), typeof(global::Grpc.Testing.ServerType), typeof(global::Grpc.Testing.RpcType), }, new pbr::GeneratedClrTypeInfo[] {
@@ -106,7 +107,7 @@ static ControlReflection() {
             new pbr::GeneratedClrTypeInfo(typeof(global::Grpc.Testing.LoadParams), global::Grpc.Testing.LoadParams.Parser, new[]{ "ClosedLoop", "Poisson" }, new[]{ "Load" }, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::Grpc.Testing.SecurityParams), global::Grpc.Testing.SecurityParams.Parser, new[]{ "UseTestCa", "ServerHostOverride", "CredType" }, null, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::Grpc.Testing.ChannelArg), global::Grpc.Testing.ChannelArg.Parser, new[]{ "Name", "StrValue", "IntValue" }, new[]{ "Value" }, null, null),
-            new pbr::GeneratedClrTypeInfo(typeof(global::Grpc.Testing.ClientConfig), global::Grpc.Testing.ClientConfig.Parser, new[]{ "ServerTargets", "ClientType", "SecurityParams", "OutstandingRpcsPerChannel", "ClientChannels", "AsyncClientThreads", "RpcType", "LoadParams", "PayloadConfig", "HistogramParams", "CoreList", "CoreLimit", "OtherClientApi", "ChannelArgs", "ThreadsPerCq", "MessagesPerStream" }, null, null, null),
+            new pbr::GeneratedClrTypeInfo(typeof(global::Grpc.Testing.ClientConfig), global::Grpc.Testing.ClientConfig.Parser, new[]{ "ServerTargets", "ClientType", "SecurityParams", "OutstandingRpcsPerChannel", "ClientChannels", "AsyncClientThreads", "RpcType", "LoadParams", "PayloadConfig", "HistogramParams", "CoreList", "CoreLimit", "OtherClientApi", "ChannelArgs", "ThreadsPerCq", "MessagesPerStream", "UseCoalesceApi" }, null, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::Grpc.Testing.ClientStatus), global::Grpc.Testing.ClientStatus.Parser, new[]{ "Stats" }, null, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::Grpc.Testing.Mark), global::Grpc.Testing.Mark.Parser, new[]{ "Reset" }, null, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::Grpc.Testing.ClientArgs), global::Grpc.Testing.ClientArgs.Parser, new[]{ "Setup", "Mark" }, new[]{ "Argtype" }, null, null),
@@ -989,6 +990,7 @@ public ClientConfig(ClientConfig other) : this() {
       channelArgs_ = other.channelArgs_.Clone();
       threadsPerCq_ = other.threadsPerCq_;
       messagesPerStream_ = other.messagesPerStream_;
+      useCoalesceApi_ = other.useCoalesceApi_;
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1198,6 +1200,20 @@ public int MessagesPerStream {
       }
     }
 
+    /// <summary>Field number for the "use_coalesce_api" field.</summary>
+    public const int UseCoalesceApiFieldNumber = 19;
+    private bool useCoalesceApi_;
+    /// <summary>
+    /// Use coalescing API when possible.
+    /// </summary>
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    public bool UseCoalesceApi {
+      get { return useCoalesceApi_; }
+      set {
+        useCoalesceApi_ = value;
+      }
+    }
+
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public override bool Equals(object other) {
       return Equals(other as ClientConfig);
@@ -1227,6 +1243,7 @@ public bool Equals(ClientConfig other) {
       if(!channelArgs_.Equals(other.channelArgs_)) return false;
       if (ThreadsPerCq != other.ThreadsPerCq) return false;
       if (MessagesPerStream != other.MessagesPerStream) return false;
+      if (UseCoalesceApi != other.UseCoalesceApi) return false;
       return true;
     }
 
@@ -1249,6 +1266,7 @@ public override int GetHashCode() {
       hash ^= channelArgs_.GetHashCode();
       if (ThreadsPerCq != 0) hash ^= ThreadsPerCq.GetHashCode();
       if (MessagesPerStream != 0) hash ^= MessagesPerStream.GetHashCode();
+      if (UseCoalesceApi != false) hash ^= UseCoalesceApi.GetHashCode();
       return hash;
     }
 
@@ -1314,6 +1332,10 @@ public void WriteTo(pb::CodedOutputStream output) {
         output.WriteRawTag(144, 1);
         output.WriteInt32(MessagesPerStream);
       }
+      if (UseCoalesceApi != false) {
+        output.WriteRawTag(152, 1);
+        output.WriteBool(UseCoalesceApi);
+      }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1361,6 +1383,9 @@ public int CalculateSize() {
       if (MessagesPerStream != 0) {
         size += 2 + pb::CodedOutputStream.ComputeInt32Size(MessagesPerStream);
       }
+      if (UseCoalesceApi != false) {
+        size += 2 + 1;
+      }
       return size;
     }
 
@@ -1423,6 +1448,9 @@ public void MergeFrom(ClientConfig other) {
       if (other.MessagesPerStream != 0) {
         MessagesPerStream = other.MessagesPerStream;
       }
+      if (other.UseCoalesceApi != false) {
+        UseCoalesceApi = other.UseCoalesceApi;
+      }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1510,6 +1538,10 @@ public void MergeFrom(pb::CodedInputStream input) {
             MessagesPerStream = input.ReadInt32();
             break;
           }
+          case 152: {
+            UseCoalesceApi = input.ReadBool();
+            break;
+          }
         }
       }
     }
diff --git a/src/csharp/Grpc.IntegrationTesting/MetricsGrpc.cs b/src/csharp/Grpc.IntegrationTesting/MetricsGrpc.cs
index f71d6d197d2a2..d18b9e7d5e7f4 100644
--- a/src/csharp/Grpc.IntegrationTesting/MetricsGrpc.cs
+++ b/src/csharp/Grpc.IntegrationTesting/MetricsGrpc.cs
@@ -26,9 +26,6 @@
 #pragma warning disable 1591
 #region Designer generated code
 
-using System;
-using System.Threading;
-using System.Threading.Tasks;
 using grpc = global::Grpc.Core;
 
 namespace Grpc.Testing {
@@ -121,7 +118,7 @@ protected MetricsServiceClient(ClientBaseConfiguration configuration) : base(con
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncServerStreamingCall<global::Grpc.Testing.GaugeResponse> GetAllGauges(global::Grpc.Testing.EmptyMessage request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncServerStreamingCall<global::Grpc.Testing.GaugeResponse> GetAllGauges(global::Grpc.Testing.EmptyMessage request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return GetAllGauges(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -144,7 +141,7 @@ protected MetricsServiceClient(ClientBaseConfiguration configuration) : base(con
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The response received from the server.</returns>
-      public virtual global::Grpc.Testing.GaugeResponse GetGauge(global::Grpc.Testing.GaugeRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.GaugeResponse GetGauge(global::Grpc.Testing.GaugeRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return GetGauge(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -166,7 +163,7 @@ protected MetricsServiceClient(ClientBaseConfiguration configuration) : base(con
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.GaugeResponse> GetGaugeAsync(global::Grpc.Testing.GaugeRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.GaugeResponse> GetGaugeAsync(global::Grpc.Testing.GaugeRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return GetGaugeAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
diff --git a/src/csharp/Grpc.IntegrationTesting/ServicesGrpc.cs b/src/csharp/Grpc.IntegrationTesting/ServicesGrpc.cs
index d2e4f2e4a5b2b..46b328a773fb9 100644
--- a/src/csharp/Grpc.IntegrationTesting/ServicesGrpc.cs
+++ b/src/csharp/Grpc.IntegrationTesting/ServicesGrpc.cs
@@ -22,9 +22,6 @@
 #pragma warning disable 1591
 #region Designer generated code
 
-using System;
-using System.Threading;
-using System.Threading.Tasks;
 using grpc = global::Grpc.Core;
 
 namespace Grpc.Testing {
@@ -177,7 +174,7 @@ protected BenchmarkServiceClient(ClientBaseConfiguration configuration) : base(c
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The response received from the server.</returns>
-      public virtual global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return UnaryCall(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -201,7 +198,7 @@ protected BenchmarkServiceClient(ClientBaseConfiguration configuration) : base(c
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> UnaryCallAsync(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> UnaryCallAsync(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return UnaryCallAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -225,7 +222,7 @@ protected BenchmarkServiceClient(ClientBaseConfiguration configuration) : base(c
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Testing.SimpleRequest, global::Grpc.Testing.SimpleResponse> StreamingCall(grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Testing.SimpleRequest, global::Grpc.Testing.SimpleResponse> StreamingCall(grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return StreamingCall(new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -248,7 +245,7 @@ protected BenchmarkServiceClient(ClientBaseConfiguration configuration) : base(c
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncClientStreamingCall<global::Grpc.Testing.SimpleRequest, global::Grpc.Testing.SimpleResponse> StreamingFromClient(grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncClientStreamingCall<global::Grpc.Testing.SimpleRequest, global::Grpc.Testing.SimpleResponse> StreamingFromClient(grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return StreamingFromClient(new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -271,7 +268,7 @@ protected BenchmarkServiceClient(ClientBaseConfiguration configuration) : base(c
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncServerStreamingCall<global::Grpc.Testing.SimpleResponse> StreamingFromServer(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncServerStreamingCall<global::Grpc.Testing.SimpleResponse> StreamingFromServer(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return StreamingFromServer(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -294,7 +291,7 @@ protected BenchmarkServiceClient(ClientBaseConfiguration configuration) : base(c
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Testing.SimpleRequest, global::Grpc.Testing.SimpleResponse> StreamingBothWays(grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Testing.SimpleRequest, global::Grpc.Testing.SimpleResponse> StreamingBothWays(grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return StreamingBothWays(new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -470,7 +467,7 @@ protected WorkerServiceClient(ClientBaseConfiguration configuration) : base(conf
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Testing.ServerArgs, global::Grpc.Testing.ServerStatus> RunServer(grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Testing.ServerArgs, global::Grpc.Testing.ServerStatus> RunServer(grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return RunServer(new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -500,7 +497,7 @@ protected WorkerServiceClient(ClientBaseConfiguration configuration) : base(conf
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Testing.ClientArgs, global::Grpc.Testing.ClientStatus> RunClient(grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Testing.ClientArgs, global::Grpc.Testing.ClientStatus> RunClient(grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return RunClient(new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -526,7 +523,7 @@ protected WorkerServiceClient(ClientBaseConfiguration configuration) : base(conf
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The response received from the server.</returns>
-      public virtual global::Grpc.Testing.CoreResponse CoreCount(global::Grpc.Testing.CoreRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.CoreResponse CoreCount(global::Grpc.Testing.CoreRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return CoreCount(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -548,7 +545,7 @@ protected WorkerServiceClient(ClientBaseConfiguration configuration) : base(conf
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.CoreResponse> CoreCountAsync(global::Grpc.Testing.CoreRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.CoreResponse> CoreCountAsync(global::Grpc.Testing.CoreRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return CoreCountAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -570,7 +567,7 @@ protected WorkerServiceClient(ClientBaseConfiguration configuration) : base(conf
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The response received from the server.</returns>
-      public virtual global::Grpc.Testing.Void QuitWorker(global::Grpc.Testing.Void request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.Void QuitWorker(global::Grpc.Testing.Void request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return QuitWorker(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -592,7 +589,7 @@ protected WorkerServiceClient(ClientBaseConfiguration configuration) : base(conf
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.Void> QuitWorkerAsync(global::Grpc.Testing.Void request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.Void> QuitWorkerAsync(global::Grpc.Testing.Void request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return QuitWorkerAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -692,7 +689,7 @@ protected ReportQpsScenarioServiceClient(ClientBaseConfiguration configuration)
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The response received from the server.</returns>
-      public virtual global::Grpc.Testing.Void ReportScenario(global::Grpc.Testing.ScenarioResult request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.Void ReportScenario(global::Grpc.Testing.ScenarioResult request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return ReportScenario(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -714,7 +711,7 @@ protected ReportQpsScenarioServiceClient(ClientBaseConfiguration configuration)
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.Void> ReportScenarioAsync(global::Grpc.Testing.ScenarioResult request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.Void> ReportScenarioAsync(global::Grpc.Testing.ScenarioResult request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return ReportScenarioAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
diff --git a/src/csharp/Grpc.IntegrationTesting/TestGrpc.cs b/src/csharp/Grpc.IntegrationTesting/TestGrpc.cs
index c0d147c15071f..6c4b77f7acdb5 100644
--- a/src/csharp/Grpc.IntegrationTesting/TestGrpc.cs
+++ b/src/csharp/Grpc.IntegrationTesting/TestGrpc.cs
@@ -23,9 +23,6 @@
 #pragma warning disable 1591
 #region Designer generated code
 
-using System;
-using System.Threading;
-using System.Threading.Tasks;
 using grpc = global::Grpc.Core;
 
 namespace Grpc.Testing {
@@ -244,7 +241,7 @@ protected TestServiceClient(ClientBaseConfiguration configuration) : base(config
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The response received from the server.</returns>
-      public virtual global::Grpc.Testing.Empty EmptyCall(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.Empty EmptyCall(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return EmptyCall(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -266,7 +263,7 @@ protected TestServiceClient(ClientBaseConfiguration configuration) : base(config
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.Empty> EmptyCallAsync(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.Empty> EmptyCallAsync(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return EmptyCallAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -288,7 +285,7 @@ protected TestServiceClient(ClientBaseConfiguration configuration) : base(config
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The response received from the server.</returns>
-      public virtual global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.SimpleResponse UnaryCall(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return UnaryCall(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -310,7 +307,7 @@ protected TestServiceClient(ClientBaseConfiguration configuration) : base(config
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> UnaryCallAsync(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> UnaryCallAsync(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return UnaryCallAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -334,7 +331,7 @@ protected TestServiceClient(ClientBaseConfiguration configuration) : base(config
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The response received from the server.</returns>
-      public virtual global::Grpc.Testing.SimpleResponse CacheableUnaryCall(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.SimpleResponse CacheableUnaryCall(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return CacheableUnaryCall(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -360,7 +357,7 @@ protected TestServiceClient(ClientBaseConfiguration configuration) : base(config
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> CacheableUnaryCallAsync(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.SimpleResponse> CacheableUnaryCallAsync(global::Grpc.Testing.SimpleRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return CacheableUnaryCallAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -385,7 +382,7 @@ protected TestServiceClient(ClientBaseConfiguration configuration) : base(config
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncServerStreamingCall<global::Grpc.Testing.StreamingOutputCallResponse> StreamingOutputCall(global::Grpc.Testing.StreamingOutputCallRequest request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncServerStreamingCall<global::Grpc.Testing.StreamingOutputCallResponse> StreamingOutputCall(global::Grpc.Testing.StreamingOutputCallRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return StreamingOutputCall(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -408,7 +405,7 @@ protected TestServiceClient(ClientBaseConfiguration configuration) : base(config
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncClientStreamingCall<global::Grpc.Testing.StreamingInputCallRequest, global::Grpc.Testing.StreamingInputCallResponse> StreamingInputCall(grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncClientStreamingCall<global::Grpc.Testing.StreamingInputCallRequest, global::Grpc.Testing.StreamingInputCallResponse> StreamingInputCall(grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return StreamingInputCall(new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -431,7 +428,7 @@ protected TestServiceClient(ClientBaseConfiguration configuration) : base(config
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Testing.StreamingOutputCallRequest, global::Grpc.Testing.StreamingOutputCallResponse> FullDuplexCall(grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Testing.StreamingOutputCallRequest, global::Grpc.Testing.StreamingOutputCallResponse> FullDuplexCall(grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return FullDuplexCall(new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -456,7 +453,7 @@ protected TestServiceClient(ClientBaseConfiguration configuration) : base(config
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Testing.StreamingOutputCallRequest, global::Grpc.Testing.StreamingOutputCallResponse> HalfDuplexCall(grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Testing.StreamingOutputCallRequest, global::Grpc.Testing.StreamingOutputCallResponse> HalfDuplexCall(grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return HalfDuplexCall(new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -481,7 +478,7 @@ protected TestServiceClient(ClientBaseConfiguration configuration) : base(config
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The response received from the server.</returns>
-      public virtual global::Grpc.Testing.Empty UnimplementedCall(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.Empty UnimplementedCall(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return UnimplementedCall(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -505,7 +502,7 @@ protected TestServiceClient(ClientBaseConfiguration configuration) : base(config
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.Empty> UnimplementedCallAsync(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.Empty> UnimplementedCallAsync(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return UnimplementedCallAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -613,7 +610,7 @@ protected UnimplementedServiceClient(ClientBaseConfiguration configuration) : ba
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The response received from the server.</returns>
-      public virtual global::Grpc.Testing.Empty UnimplementedCall(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.Empty UnimplementedCall(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return UnimplementedCall(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -635,7 +632,7 @@ protected UnimplementedServiceClient(ClientBaseConfiguration configuration) : ba
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.Empty> UnimplementedCallAsync(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.Empty> UnimplementedCallAsync(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return UnimplementedCallAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -734,7 +731,7 @@ protected ReconnectServiceClient(ClientBaseConfiguration configuration) : base(c
       {
       }
 
-      public virtual global::Grpc.Testing.Empty Start(global::Grpc.Testing.ReconnectParams request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.Empty Start(global::Grpc.Testing.ReconnectParams request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return Start(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -742,7 +739,7 @@ protected ReconnectServiceClient(ClientBaseConfiguration configuration) : base(c
       {
         return CallInvoker.BlockingUnaryCall(__Method_Start, null, options, request);
       }
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.Empty> StartAsync(global::Grpc.Testing.ReconnectParams request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.Empty> StartAsync(global::Grpc.Testing.ReconnectParams request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return StartAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -750,7 +747,7 @@ protected ReconnectServiceClient(ClientBaseConfiguration configuration) : base(c
       {
         return CallInvoker.AsyncUnaryCall(__Method_Start, null, options, request);
       }
-      public virtual global::Grpc.Testing.ReconnectInfo Stop(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual global::Grpc.Testing.ReconnectInfo Stop(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return Stop(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
@@ -758,7 +755,7 @@ protected ReconnectServiceClient(ClientBaseConfiguration configuration) : base(c
       {
         return CallInvoker.BlockingUnaryCall(__Method_Stop, null, options, request);
       }
-      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.ReconnectInfo> StopAsync(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncUnaryCall<global::Grpc.Testing.ReconnectInfo> StopAsync(global::Grpc.Testing.Empty request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return StopAsync(request, new grpc::CallOptions(headers, deadline, cancellationToken));
       }
diff --git a/src/csharp/Grpc.Reflection/ReflectionGrpc.cs b/src/csharp/Grpc.Reflection/ReflectionGrpc.cs
index 0195186eba99c..e2263cfc90c54 100644
--- a/src/csharp/Grpc.Reflection/ReflectionGrpc.cs
+++ b/src/csharp/Grpc.Reflection/ReflectionGrpc.cs
@@ -22,9 +22,6 @@
 #pragma warning disable 1591
 #region Designer generated code
 
-using System;
-using System.Threading;
-using System.Threading.Tasks;
 using grpc = global::Grpc.Core;
 
 namespace Grpc.Reflection.V1Alpha {
@@ -97,7 +94,7 @@ protected ServerReflectionClient(ClientBaseConfiguration configuration) : base(c
       /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
       /// <param name="cancellationToken">An optional token for canceling the call.</param>
       /// <returns>The call object.</returns>
-      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Reflection.V1Alpha.ServerReflectionRequest, global::Grpc.Reflection.V1Alpha.ServerReflectionResponse> ServerReflectionInfo(grpc::Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+      public virtual grpc::AsyncDuplexStreamingCall<global::Grpc.Reflection.V1Alpha.ServerReflectionRequest, global::Grpc.Reflection.V1Alpha.ServerReflectionResponse> ServerReflectionInfo(grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
         return ServerReflectionInfo(new grpc::CallOptions(headers, deadline, cancellationToken));
       }