title: Targeting the MONO Runtime causes Xamarin Build to fail
body: <p>After creating a simple .NET console application in Xamarin Studio, I can build/debug fine if the default Target Runtime is set to 'Microsoft .NET'.</p>
  
  <p>If I set the runtime to MONO ('Mono 4.0.1'), then my project no longer builds. </p>
  
  <p>The error is:</p>
  
  <blockquote>
    <p>Error: Unknown MSBuild failure. Please try building the project again</p>
  </blockquote>
  
  <p>The build output window shows everything succeeding up until the last line, which displays
  <strong>Build: 1 error, 0 warnings</strong>":</p>
  
  <p>Is targeting the MONO Runtime in this way not valid? A related question <a href="https://stackoverflow.com/questions/19041236/force-xamarin-to-use-mono-on-windows">here</a> indicates that it is... </p>
  
  <p>What am I doing wrong?</p>
  
  <p>Running Windows7 (64 bit), Xamarin Studio 5.9. Mono 4.0.1, .NET 4.5</p>
  
  <p>The build output is as follows:</p>
  
  <blockquote>
    <p>Cleaning Solution: XamarinTest (Debug)</p>
    
    <p>Cleaning: XamarinTest (Debug)</p>
    
    <p>Build started 05/08/2015 16:57:03.
    __________________________________________________ Project "C:\Development\Test\XamarinTest\XamarinTest\XamarinTest.csproj"
    (Clean target(s)):        Target CoreClean:       Deleting file
    'C:\Development\Test\XamarinTest\XamarinTest\obj\Debug.NETFramework,Version=v4.5.AssemblyAttribute.cs'
          Deleting file
    'C:\Development\Test\XamarinTest\XamarinTest\bin\Debug\XamarinTest.dll.mdb'
          Deleting file
    'C:\Development\Test\XamarinTest\XamarinTest\bin\Debug\XamarinTest.dll'
          Deleting file
    'C:\Development\Test\XamarinTest\XamarinTest\obj\Debug\XamarinTest.dll'
          Deleting file
    'C:\Development\Test\XamarinTest\XamarinTest\obj\Debug\XamarinTest.dll.mdb'
          Deleting file
    'C:\Development\Test\XamarinTest\XamarinTest\obj\Debug\XamarinTest.csproj.FilesWrittenAbsolute.txt'
    Done building project
    "C:\Development\Test\XamarinTest\XamarinTest\XamarinTest.csproj".</p>
    
    <p>Build succeeded.   0 Error(s)      0 Warning(s)</p>
    
    <p>Time Elapsed 00:00:00.1350135</p>
    
    <p>Cleaning: XamConsole (Debug)</p>
    
    <p>Build started 05/08/2015 16:57:04.
    __________________________________________________ Project "C:\Development\Test\XamarinTest\XamConsole\XamConsole.csproj" (Clean
    target(s)):       Target CoreClean:       Deleting file
    'C:\Development\Test\XamarinTest\XamConsole\obj\Debug\XamConsole.exe'
    Done building project
    "C:\Development\Test\XamarinTest\XamConsole\XamConsole.csproj".</p>
    
    <p>Build succeeded.   0 Warning(s)    0 Error(s)</p>
    
    <p>Time Elapsed 00:00:00.0170017</p>
    
    <p>Building Solution: XamarinTest (Debug)</p>
    
    <p>Building: XamarinTest (Debug)</p>
    
    <p>Build started 05/08/2015 16:57:04.
    __________________________________________________ Project "C:\Development\Test\XamarinTest\XamarinTest\XamarinTest.csproj"
    (Build target(s)):        Target PrepareForBuild:         Configuration: Debug
    Platform: AnyCPU      Target GenerateSatelliteAssemblies:     No input
    files were specified for target GenerateSatelliteAssemblies, skipping.
          Target CoreCompile:         Tool C:\Program Files
    (x86)\Mono\lib\mono\4.5\mcs.exe execution started with arguments:
    /noconfig /debug:full /debug+ /optimize-
    /out:obj\Debug\XamarinTest.dll MyClass.cs Properties\AssemblyInfo.cs
    obj\Debug.NETFramework,Version=v4.5.AssemblyAttribute.cs
    /target:library /define:DEBUG /nostdlib /reference:"C:\Program Files
    (x86)\Mono\lib\mono\4.5..\xbuild-frameworks.NETFramework\v4.5\RedistList........\4.5\System.dll"
    /reference:"C:\Program Files
    (x86)\Mono\lib\mono\4.5..\xbuild-frameworks.NETFramework\v4.5\RedistList........\4.5\System.Core.dll"
    /reference:"C:\Program Files (x86)\Mono\lib\mono\4.5\mscorlib.dll"
    /warn:4       Target DeployOutputFiles:       Copying file from
    'C:\Development\Test\XamarinTest\XamarinTest\obj\Debug\XamarinTest.dll.mdb'
    to
    'C:\Development\Test\XamarinTest\XamarinTest\bin\Debug\XamarinTest.dll.mdb'
          Copying file from
    'C:\Development\Test\XamarinTest\XamarinTest\obj\Debug\XamarinTest.dll'
    to
    'C:\Development\Test\XamarinTest\XamarinTest\bin\Debug\XamarinTest.dll'
    Done building project
    "C:\Development\Test\XamarinTest\XamarinTest\XamarinTest.csproj".</p>
    
    <p>Build succeeded.   0 Warning(s)    0 Error(s)</p>
    
    <p>Time Elapsed 00:00:08.6528652</p>
    
    <p>---------------------- Done ----------------------</p>
    
    <p><strong>Build: 1 error, 0 warnings</strong></p>
  </blockquote>