title: Visual Studio 2010 - Can't step through .NET Framework 4 source (PresentationCore.dll)
body: <p><strong>The problem:</strong> I'm getting a nullref inside of System.Windows.Interop.HwndKeyboardInputProvider's FilterMessage method that I'd really like to try to debug, but without being able to step through the source I'm not sure what else to do.</p>
  
  <p><strong>I've tried</strong>
  Setting up Visual Studio 2010 to allow me to step through the .NET Framework source (specifically System.Windows.Interop.HwndKeyboardInputProvider's FilterMessage method, in PresentationCore.dll). I'm having trouble getting my visual studio to display .NET source for debugging. I've followed various different articles/blog entires, but nothing seems to be working. What I've tried:</p>
  
  <p>In the VS2010 Options->Debugging menu, enabling "Enable .NET Framework source stepping", enaling "Enable source server support", disabling "Require source files to exactly match the original version",
  following the instructions here: (<a href="http://blogs.microsoft.co.il/blogs/arik/archive/2010/07/12/step-into-net-framework-4-0-source-code.aspx" rel="noreferrer">http://blogs.microsoft.co.il/blogs/arik/archive/2010/07/12/step-into-net-framework-4-0-source-code.aspx</a>) and installing the reference source and setting up VS to use the symbol files included with the reference source, along with several other attempts based on articles/blog entries online. Using that method, I can see in my modules window that the symbols for PresentationCore.dll are being loaded, but I still get the "No source available" window when trying to step into the area I'm trying to debug.</p>
  
  <p>Modules window showing that Symbols are being loaded from the path where I installed the .NET 4 reference source:
  <img src="https://i.stack.imgur.com/dgGPe.png" alt="enter image description here"></p>
  
  <p>Call stack showing that it seems like I <em>should</em> be able to step into PresentationCore.dll's System.Windows.Interop.HwndKeyboardInputProvider.FilterMessage method:
  <img src="https://i.stack.imgur.com/Gy3j2.png" alt="enter image description here"></p>
  
  <p>The "No Source Available" window, with "Browse to Find Source" disabled:
  <img src="https://i.stack.imgur.com/j1f8o.png" alt="enter image description here"></p>
  
  <p>I'm not really sure what else to try? </p>