Unable to debug managed code using visual studio 2013 (“Cannot evaluate expression” error - am using debug build) (Note that VS 2012 works)

Question

I have .net application (GUI as well as PowerShell) built against 4.5. My OS is server 2012. When I attach my application to 2013 visual studio, the debugger is not working

Answer 1

I deleted all my breakpoints and then it started working, with Visual Studio 2013 Update 1. This was one of the suggestions from the blog post mentioned by Dreamer.

Answer 2

I had a similar problem debugging where this error occurred from a return from creating a class. The class initialized fine (using "new classname()") but then it gave the "cannot evaluate expression" error on the return. Though it worked on previous visual studio versions, running on VS 2017 it crapped out.

After a lot of head banging, it turned out that private variables in the class, especially things like arraylists and other classes, needed to be declared with initial values, even if set to null.

Once that was done, everything worked, even though the solution "appeared" to have nothing to do with the problem and gave no apparent clue of where the problem occurred.

Answer 3

We have a custom expression evaluator and our own language and this warning message to change the settings always appears even after I change the project settings to those specified in the blog.

 <DebugEngines>{351668CC-8477-4fbf-BFE3-5F1006E4DB1F}</DebugEngines>

Is there something else?

Our clients are using VS2013 pro. I've turned off all the "Enable the Visual Studio hosting process" for all our projects and also added the property to our clients projects. I still see the warning each time I attack to w3wp.exe.

IMPORTANT NOTE: If your project is using the Visual Studio hosting process (the default for many project types), you must disable the hosting process for this fix to correctly change the debug mode. To disable the hosting process go to the Debug pane on the project properties page, and uncheck "Enable the Visual Studio hosting process"