feat: Detect grpc-dotnet support on Windows under .NET Framework

This will enable more users to use grpc-dotnet instead of Grpc.Core.

Comprehensive testing is impractical, but this has been tested under Windows 10 (uses Grpc.Core) and Windows 11 (uses Grpc.Net.Client).

Fixes #712.

Note that we'll need to revisit code if a later version of Windows
Server 2022 fully supports grpc-dotnet.

Google.Api.Gax.Grpc/GrpcAdapter.cs

@@ -128,29 +128,12 @@ private static GrpcAdapter DetectDefaultGrpcTransportAdapterPreferringGrpcNetCli
             }
             // Test 2, only for .NET Framework: check what version of Windows we're using.
 #if NET462_OR_GREATER
-            if (!PlatformFullySupportsGrpc())
+            if (!GrpcWindowsDetection.PlatformFullySupportsGrpc())
             {
                 return GrpcCoreAdapter.Instance;
             }
 #endif
             return GrpcNetClientAdapter.Default;
-
-
-#if NET462_OR_GREATER
-            // gRPC support on .NET Framework is complex.
-            // - Some Windows platforms don't support it at all, in which case an exception is thrown
-            //   in GrpcChannel.ForAddress, which is handled above.
-            // - Other platforms support it partially - unary and server-streaming, but not
-            //   bidi- or client-streaming.
-            // - Other platforms support it fully.
-            //
-            // While in theory we could tailor the default instance for a given service to whether
-            // streaming is required or not, that would lead to a very inconsistent experience.
-            // At some point, we wish to check the Windows version details and use that to determine
-            // which adapter to use, but for now we'll always use Grpc.Core.
-            // Once https://github.com/grpc/grpc-dotnet/issues/2242 is fixed, we can use that code.
-            static bool PlatformFullySupportsGrpc() => false;
-#endif
         }
     }
 }

Google.Api.Gax.Grpc/GrpcWindowsDetection.cs

@@ -0,0 +1,100 @@
+/*
+ * Copyright 2024 Google LLC
+ * Use of this source code is governed by a BSD-style
+ * license that can be found in the LICENSE file or at
+ * https://developers.google.com/open-source/licenses/bsd
+ */
+
+#if NET462_OR_GREATER
+
+using System.Runtime.InteropServices;
+using System;
+
+internal static class GrpcWindowsDetection
+{
+    // gRPC support on .NET Framework is complex.
+    // - Some Windows platforms don't support it at all, in which case an exception is thrown
+    //   in GrpcChannel.ForAddress, which is handled above.
+    // - Other platforms support it partially - unary and server-streaming, but not
+    //   bidi- or client-streaming.
+    // - Other platforms support it fully.
+    //
+    // While in theory we could tailor the default instance for a given service to whether
+    // streaming is required or not, that would lead to a very inconsistent experience.
+    // We attempt to detect which version of Windows we're on, erring on the side of caution.
+    // Code based on https://gist.github.com/tonydnewell/6a663b7258ce3599e6bdae5c4291b2a6
+    internal static bool PlatformFullySupportsGrpc()
+    {
+        // If we're running on Mono or similar, all bets are off.
+        if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+        {
+            return false;
+        }
+        // Older versions of .NET report an OSVersion.Version based on Windows compatibility settings.
+        // For example, if an app running on Windows 11 is configured to be "compatible" with Windows 10
+        // then the version returned is always Windows 10.
+        //
+        // Get correct Windows version directly from Windows by calling RtlGetVersion.
+        // https://www.pinvoke.net/default.aspx/ntdll/RtlGetVersion.html
+
+        DetectWindowsVersion(out var windowsVersion, out var windowsServer);
+
+        const int Windows11BuildVersion = 22000;
+
+        // Windows 11 has full support.
+        // Currently, Windows Server (even 2022) doesn't fully support gRPC under .NET Framework.
+        // When there's a version that does, we can update this check.
+        return windowsVersion.Build >= Windows11BuildVersion;
+    }
+
+    /// <summary>
+    /// Types for calling RtlGetVersion. See https://www.pinvoke.net/default.aspx/ntdll/RtlGetVersion.html
+    /// </summary>
+#pragma warning disable SYSLIB1054 // Use 'LibraryImportAttribute' instead of 'DllImportAttribute' to generate P/Invoke marshalling code at compile time
+    [DllImport("ntdll.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+    private static extern NTSTATUS RtlGetVersion(ref OSVERSIONINFOEX versionInfo);
+#pragma warning restore SYSLIB1054 // Use 'LibraryImportAttribute' instead of 'DllImportAttribute' to generate P/Invoke marshalling code at compile time
+
+    private static void DetectWindowsVersion(out Version version, out bool isWindowsServer)
+    {
+        // https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-osversioninfoexa
+        const byte VER_NT_SERVER = 3;
+
+        var osVersionInfo = new OSVERSIONINFOEX { OSVersionInfoSize = Marshal.SizeOf<OSVERSIONINFOEX>() };
+
+        if (RtlGetVersion(ref osVersionInfo) != NTSTATUS.STATUS_SUCCESS)
+        {
+            throw new InvalidOperationException($"Failed to call internal {nameof(RtlGetVersion)}.");
+        }
+
+        version = new Version(osVersionInfo.MajorVersion, osVersionInfo.MinorVersion, osVersionInfo.BuildNumber, 0);
+        isWindowsServer = osVersionInfo.ProductType == VER_NT_SERVER;
+    }
+
+    private enum NTSTATUS : uint
+    {
+        /// <summary>
+        /// The operation completed successfully. 
+        /// </summary>
+        STATUS_SUCCESS = 0x00000000
+    }
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    private struct OSVERSIONINFOEX
+    {
+        // The OSVersionInfoSize field must be set to Marshal.SizeOf(typeof(OSVERSIONINFOEX))
+        public int OSVersionInfoSize;
+        public int MajorVersion;
+        public int MinorVersion;
+        public int BuildNumber;
+        public int PlatformId;
+        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
+        public string CSDVersion;
+        public ushort ServicePackMajor;
+        public ushort ServicePackMinor;
+        public short SuiteMask;
+        public byte ProductType;
+        public byte Reserved;
+    }
+}
+#endif