Run tests for supported platfroms

appveyor.bat

@@ -38,8 +38,8 @@ dotnet restore
 dotnet build -c %configuration% || goto error
 
 echo Testing C#
-dotnet test -c %configuration% -f netcoreapp3.1 Google.Protobuf.Test\Google.Protobuf.Test.csproj || goto error
-dotnet test -c %configuration% -f net451 Google.Protobuf.Test\Google.Protobuf.Test.csproj || goto error
+dotnet test -c %configuration% -f net6.0 Google.Protobuf.Test\Google.Protobuf.Test.csproj || goto error
+dotnet test -c %configuration% -f net462 Google.Protobuf.Test\Google.Protobuf.Test.csproj || goto error
 
 goto :EOF
 

csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Google.Protobuf.Test.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFrameworks>net451;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net462;net6.0</TargetFrameworks>
     <AssemblyOriginatorKeyFile>../../keys/Google.Protobuf.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>
     <IsPackable>False</IsPackable>
@@ -18,9 +18,9 @@
     <PackageReference Include="NUnitLite" Version="3.6.1" />
   </ItemGroup>
 
-  <!-- Needed for the net45 build to work on Unix. See https://github.com/dotnet/designs/pull/33 -->
+  <!-- Needed for the netfx build to work on Unix. See https://github.com/dotnet/designs/pull/33 -->
   <ItemGroup>
-    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0-preview.2" PrivateAssets="All" />
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.2" PrivateAssets="All" />
   </ItemGroup>
 
 </Project>

csharp/src/AddressBook/AddressBook.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
     <OutputType>Exe</OutputType>
     <StartupObject>Google.Protobuf.Examples.AddressBook.Program</StartupObject>
     <IsPackable>False</IsPackable>

csharp/src/Google.Protobuf.Conformance/Google.Protobuf.Conformance.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
     <OutputType>Exe</OutputType>
     <IsPackable>False</IsPackable>
   </PropertyGroup>

csharp/src/Google.Protobuf.JsonDump/Google.Protobuf.JsonDump.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
     <OutputType>Exe</OutputType>
     <IsPackable>False</IsPackable>
   </PropertyGroup>

csharp/src/Google.Protobuf.Test.TestProtos/Google.Protobuf.Test.TestProtos.csproj

@@ -6,14 +6,14 @@
     and without the internal visibility from the test project (all of which have caused issues in the past).
   -->
   <PropertyGroup>
-    <TargetFrameworks>net462;netstandard1.1;netstandard2.0</TargetFrameworks>
+    <TargetFrameworks>net462;netstandard2.0</TargetFrameworks>
     <LangVersion>10.0</LangVersion>
     <AssemblyOriginatorKeyFile>../../keys/Google.Protobuf.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>
     <IsPackable>False</IsPackable>
   </PropertyGroup>
 
-  <!-- Needed for the net45 build to work on Unix. See https://github.com/dotnet/designs/pull/33 -->
+  <!-- Needed for the netfx build to work on Unix. See https://github.com/dotnet/designs/pull/33 -->
   <ItemGroup>
     <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.2" PrivateAssets="All" />
   </ItemGroup>

csharp/src/Google.Protobuf.Test/Google.Protobuf.Test.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net462;netcoreapp3.1;net60</TargetFrameworks>
+    <TargetFrameworks>net462;net6.0</TargetFrameworks>
     <AssemblyOriginatorKeyFile>../../keys/Google.Protobuf.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>
     <IsPackable>False</IsPackable>
@@ -14,12 +14,12 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.1.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.5.0" />
     <PackageReference Include="NUnit" Version="3.13.3" />
-    <PackageReference Include="NUnit3TestAdapter" Version="4.2.1" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.2.2" />
   </ItemGroup>
 
-  <!-- Needed for the net45 build to work on Unix. See https://github.com/dotnet/designs/pull/33 -->
+  <!-- Needed for the netfx build to work on Unix. See https://github.com/dotnet/designs/pull/33 -->
   <ItemGroup>
     <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.2" PrivateAssets="All" />
   </ItemGroup>

csharp/src/Google.Protobuf/WritingPrimitives.cs

@@ -50,7 +50,7 @@ namespace Google.Protobuf
     [SecuritySafeCritical]
     internal static class WritingPrimitives
     {
-#if NET5_0
+#if NET5_0_OR_GREATER
         internal static Encoding Utf8Encoding => Encoding.UTF8; // allows JIT to devirtualize
 #else
         internal static readonly Encoding Utf8Encoding = Encoding.UTF8; // "Local" copy of Encoding.UTF8, for efficiency. (Yes, it makes a difference.)