From 34b3bf6c05afd55ca6c5e6e6c05330d7ad9ea41a Mon Sep 17 00:00:00 2001
From: Matt Lyons <matt_lyons@sil.org>
Date: Thu, 29 Aug 2024 09:06:56 -0500
Subject: [PATCH] Log exception messages on .NET 6+ when dynamic library
 loading fails (#204)

---
 source/icu.net/NativeMethods/NativeMethods.cs | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/source/icu.net/NativeMethods/NativeMethods.cs b/source/icu.net/NativeMethods/NativeMethods.cs
index cc6ab483..2cca9955 100644
--- a/source/icu.net/NativeMethods/NativeMethods.cs
+++ b/source/icu.net/NativeMethods/NativeMethods.cs
@@ -347,14 +347,16 @@ private static IntPtr GetIcuLibHandle(string basename, int icuVersion)
 				var libPath = string.IsNullOrEmpty(_IcuPath) ? libName : Path.Combine(_IcuPath, libName);
 
 #if NET6_0_OR_GREATER
+				string exceptionErrorMessage = null;
 				loadMethod = "NativeLibrary.Load";
 				try
 				{
 					handle = NativeLibrary.Load(libPath);
 				}
-				catch (DllNotFoundException)
+				catch (DllNotFoundException ex)
 				{
 					handle = IntPtr.Zero;
+					exceptionErrorMessage = ex.Message;
 				}
 #else
 				if (IsWindows)
@@ -385,14 +387,16 @@ private static IntPtr GetIcuLibHandle(string basename, int icuVersion)
 
 				lastError = Marshal.GetLastWin32Error();
 #if NET6_0_OR_GREATER
+				if (!string.IsNullOrEmpty(exceptionErrorMessage))
+					exceptionErrorMessage = $" ({exceptionErrorMessage})";
 				var errorMsg = IsWindows
-					? new Win32Exception(lastError).Message
-					: $"{lastError}";
+					? $"{new Win32Exception(lastError).Message}{exceptionErrorMessage}"
+					: $"{lastError}({exceptionErrorMessage})";
 #else
 				var errorMsg = IsWindows
 					? new Win32Exception(lastError).Message
 					: IsMac
-					? $"{lastError}"
+					? $"{lastError} (macOS loading requires .NET 6 or greater)"
 					: $"{lastError} ({dlerror()})";
 #endif
 				Trace.WriteLineIf(lastError != 0, $"Unable to load [{libPath}]. Error: {errorMsg}");