title: How do I get Mono to use the right 'ToolsVersion'?
body: <pre><code>XBuild Engine Version 12.0
  Mono, Version 3.2.8.0
  </code></pre>
  
  <p>I'm trying to build my C# solution in XBuild. It builds absolutely fine in Windows, but not on Ubuntu. I get the following errors:</p>
  
  <pre><code>warning : Project has unknown ToolsVersion '14.0'. Using the default tools version '4.0' instead.
  Target GetFrameworkPaths:
  /usr/lib/mono/4.5/Microsoft.Common.targets:  warning : TargetFrameworkVersion 'v4.5.2' not supported by this toolset (ToolsVersion: 4.0).
  error CS0246: The type or namespace name 'RedditSharp' could not be found. Are you missing an assembly reference?
  error CS0246: The type or namespace name `IReadOnlyCollection' could not be found. Are you missing an assembly reference?
  </code></pre>
  
  <p>and similar. I have added RedditSharp.dll to the GAC, so I don't know why it can't find it, and I certainly don't know why it can't find IReadOnlyCollection. I have a suspicion that it's all because I can't use ToolsVersion 14.0.</p>
  
  <p>Does anybody know anything about building C# on Linux? What am I doing wrong?</p>