Revert "THRIFT-3000 .NET implementation has trouble with mixed IP modes"

This reverts commit 018c1b8f77e7d69da61014437d5f04fedbaad81d.
diff --git a/lib/csharp/test/ThriftTest/ThriftTest.csproj b/lib/csharp/test/ThriftTest/ThriftTest.csproj
index 5f9f151..d671997 100644
--- a/lib/csharp/test/ThriftTest/ThriftTest.csproj
+++ b/lib/csharp/test/ThriftTest/ThriftTest.csproj
@@ -28,7 +28,7 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>ThriftTest</RootNamespace>
     <AssemblyName>ThriftTest</AssemblyName>
-    <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <IsWebBootstrapper>false</IsWebBootstrapper>
     <FileUpgradeFlags>
@@ -136,6 +136,6 @@
 for %25%25I in ("%25OUTPUT_DIR%25") do set SHORT_DIR=%25%25~fsI
 for %25%25I in ("%25THRIFT_FILE%25") do set THRIFT_SHORT=%25%25~fsI
 "$(ProjectDir)\..\..\..\..\compiler\cpp\thrift.exe" --gen csharp -o %25SHORT_DIR%25 %25THRIFT_SHORT%25
-"$(MSBuildToolsPath)\Csc.exe" /t:library /out:"$(ProjectDir)ThriftImpl.dll" /recurse:"$(ProjectDir)gen-csharp"\* /reference:"$(ProjectDir)..\..\src\bin\Debug\Thrift.dll"</PreBuildEvent>
+$(MSBuildToolsPath)\Csc.exe /t:library /out:"$(ProjectDir)ThriftImpl.dll" /recurse:"$(ProjectDir)gen-csharp"\* /reference:"$(ProjectDir)..\..\src\bin\Debug\Thrift.dll"</PreBuildEvent>
   </PropertyGroup>
 </Project>
\ No newline at end of file