title: How to compile c# csproj into exe in Visual Studio 2015 - error CS0579
body: <p>Pretty new to C# and Visual Studio. I started with a .exe that needed modification, decompiled it in .NET Reflector, then opened the Assembly in Visual Studio 2015. I have made my change and clicked "Build" and now I get two errors with code "CS0579... Description: Duplicate 'global::System.Runtime.Versioning.TargetFrameworkAttribute' attribute" (the second is the same but without 'global::')</p>
  
  <p>I don't have a reputation of 10 yet, so I cannot post my screenshot.</p>
  
  <p>Need to get past this. any Help is welcome. Thanks!</p>