Simplify trace naming logic.

src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipeController.cs

@@ -221,7 +221,7 @@ private static EventPipeConfiguration BuildConfigFromFile(string configFilePath)
             }
 
             // Build the full path to the trace file.
-            string traceFileName = BuildTraceFileName(multiFileSec > 0);
+            string traceFileName = BuildTraceFileName();
             string outputFile = Path.Combine(outputPath, traceFileName);
 
             // Get the circular buffer size.
@@ -252,7 +252,7 @@ private static EventPipeConfiguration BuildConfigFromFile(string configFilePath)
         private static EventPipeConfiguration BuildConfigFromEnvironment()
         {
             // Build the full path to the trace file.
-            string traceFileName = BuildTraceFileName(false);
+            string traceFileName = BuildTraceFileName();
             string outputFilePath = Path.Combine(Config_EventPipeOutputPath, traceFileName);
 
             // Create a new configuration object.
@@ -281,19 +281,9 @@ private static string BuildConfigFileName()
             return GetAppName() + ConfigFileSuffix;
         }
 
-        private static string BuildTraceFileName(bool multiFile)
+        private static string BuildTraceFileName()
         {
-            string traceFileName;
-            if (multiFile)
-            {
-                traceFileName = GetAppName() + "." + Win32Native.GetCurrentProcessId();
-            }
-            else
-            {
-                traceFileName = GetAppName() + "." + Win32Native.GetCurrentProcessId() + NetPerfFileExtension;
-            }
-
-            return traceFileName;
+            return GetAppName() + "." + Win32Native.GetCurrentProcessId() + NetPerfFileExtension;
         }
 
         private static string GetAppName()

src/vm/eventpipe.cpp

@@ -618,13 +618,21 @@ void EventPipe::GetNextFilePath(EventPipeSession *pSession, SString &nextTraceFi
     }
     CONTRACTL_END;
 
-    // If multiFileTraceLengthInSeconds == 0 then s_pOutputPath is the full path to the trace file.
-    // Otherwise s_pOutputPath is the path and base name of the trace file.  It needs the file index and suffix appended to it to produce the fill path.
+    // Set the full path to the requested trace file as the next file path.
     nextTraceFilePath.Set(s_pOutputPath);
 
+    // If multiple files have been requested, then add a sequence number to the trace file name.
     UINT64 multiFileTraceLengthInSeconds = pSession->GetMultiFileTraceLengthInSeconds();
     if(multiFileTraceLengthInSeconds > 0)
     {
+        // Remove the ".netperf" file extension if it exists.
+        SString::Iterator netPerfExtension = nextTraceFilePath.End();
+        if(nextTraceFilePath.FindBack(netPerfExtension, W(".netperf")))
+        {
+            nextTraceFilePath.Truncate(netPerfExtension);
+        }
+
+        // Add the sequence number and the ".netperf" file extension.
         WCHAR strNextIndex[21];
         swprintf_s(strNextIndex, 21, W(".%u.netperf"), s_nextFileIndex++);
         nextTraceFilePath.Append(strNextIndex);