upgrade to dotnetcore 3.1 and fixed tests

libraries/csharp_dotnetcore/csharp_dotnetcore.sln

@@ -14,8 +14,8 @@ Global
 		Release|Any CPU = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
-		{D5D41DA1-02EB-4586-BD99-5547D8DED496}.Debug - NuGet Packages|Any CPU.ActiveCfg = Debug - NuGet Packages|Any CPU
-		{D5D41DA1-02EB-4586-BD99-5547D8DED496}.Debug - NuGet Packages|Any CPU.Build.0 = Debug - NuGet Packages|Any CPU
+		{D5D41DA1-02EB-4586-BD99-5547D8DED496}.Debug - NuGet Packages|Any CPU.ActiveCfg = Debug|Any CPU
+		{D5D41DA1-02EB-4586-BD99-5547D8DED496}.Debug - NuGet Packages|Any CPU.Build.0 = Debug|Any CPU
 		{D5D41DA1-02EB-4586-BD99-5547D8DED496}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{D5D41DA1-02EB-4586-BD99-5547D8DED496}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{D5D41DA1-02EB-4586-BD99-5547D8DED496}.Release|Any CPU.ActiveCfg = Release|Any CPU

libraries/csharp_dotnetcore/tests/Microsoft.Bot.Builder.Adapters.WeChat.Tests/AdapterTest.cs

@@ -50,13 +50,13 @@ namespace Microsoft.Bot.Builder.Adapters.WeChat.Tests
             await testAdapter2.ProcessAsync(request, response, bot, secretInfo).ConfigureAwait(false);
 
             var nullRequest = await Assert.ThrowsAsync<ArgumentNullException>(() => testAdapter.ProcessAsync(null, response, bot, secretInfo)).ConfigureAwait(false);
-            Assert.Equal("Value cannot be null.\r\nParameter name: httpRequest", nullRequest.Message);
+            Assert.Equal("Value cannot be null. (Parameter 'httpRequest')", nullRequest.Message);
             var nullResponse = await Assert.ThrowsAsync<ArgumentNullException>(() => testAdapter.ProcessAsync(request, null, bot, secretInfo)).ConfigureAwait(false);
-            Assert.Equal("Value cannot be null.\r\nParameter name: httpResponse", nullResponse.Message);
+            Assert.Equal("Value cannot be null. (Parameter 'httpResponse')", nullResponse.Message);
             var nullBot = await Assert.ThrowsAsync<ArgumentNullException>(() => testAdapter.ProcessAsync(request, response, null, secretInfo)).ConfigureAwait(false);
-            Assert.Equal("Value cannot be null.\r\nParameter name: bot", nullBot.Message);
+            Assert.Equal("Value cannot be null. (Parameter 'bot')", nullBot.Message);
             var nullSecretInfo = await Assert.ThrowsAsync<ArgumentNullException>(() => testAdapter.ProcessAsync(request, response, bot, null)).ConfigureAwait(false);
-            Assert.Equal("Value cannot be null.\r\nParameter name: secretInfo", nullSecretInfo.Message);
+            Assert.Equal("Value cannot be null. (Parameter 'secretInfo')", nullSecretInfo.Message);
 
             secretInfo.EchoString = "echoString";
             await testAdapter.ProcessAsync(request, response, bot, secretInfo).ConfigureAwait(false);

libraries/csharp_dotnetcore/tests/Microsoft.Bot.Builder.Adapters.WeChat.Tests/MessageCryptographyTest.cs

@@ -23,7 +23,7 @@ namespace Microsoft.Bot.Builder.Adapters.WeChat.Tests
         public void EncodingAESKeyTest()
         {
             var result = Assert.Throws<ArgumentException>(() => new MessageCryptography(MockDataUtility.SecretInfoAesKeyError, MockDataUtility.WeChatSettingsAesKeyError));
-            Assert.Equal("Invalid EncodingAESKey.\r\nParameter name: secretInfo", result.Message);
+            Assert.Equal("Invalid EncodingAESKey. (Parameter 'secretInfo')", result.Message);
         }
 
         [Fact]

libraries/csharp_dotnetcore/tests/Microsoft.Bot.Builder.Adapters.WeChat.Tests/Microsoft.Bot.Builder.Adapters.WeChat.Tests.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <TargetFrameworkVersion></TargetFrameworkVersion>
-    <TargetFramework>netcoreapp2.2</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
     <IsPackable>false</IsPackable>
   </PropertyGroup>