Show "C# 5.0" in upgrade project view if .NET 4.5 is installed.

src/AddIns/BackendBindings/CSharpBinding/Project/Src/Project/CSharpProject.cs

@@ -90,7 +90,7 @@ namespace CSharpBinding
 		
 		static readonly CompilerVersion msbuild20 = new CompilerVersion(new Version(2, 0), "C# 2.0");
 		static readonly CompilerVersion msbuild35 = new CompilerVersion(new Version(3, 5), "C# 3.0");
-		static readonly CompilerVersion msbuild40 = new CompilerVersion(new Version(4, 0), "C# 4.0");
+		static readonly CompilerVersion msbuild40 = new CompilerVersion(new Version(4, 0), DotnetDetection.IsDotnet45Installed() ? "C# 5.0" : "C# 4.0");
 		
 		public override CompilerVersion CurrentCompilerVersion {
 			get {