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If you are using Visual Studio 2015, you might have encountered this error “Internal error in the expression evaluator” while debugging your code; the debugger and the watch window will start throwing this error instead of returning the value.


If you encounter this issue and came to this page by searching online, just hold your breath. We will show you, how to fix this error and continue working with Visual Studio normally.


“Internal error in the expression evaluator” - A quick to resolve this Visual Studio 2015 error (


In case you faced this issue, when your favorite Visual Studio 2015 IDE started throwing the error “Internal error in the expression evaluator” while evaluating any variable in debug mode or in the watch window, this is due to a bug and there’s an simple tweak to resolve this error.


To resolve this error, open the Visual Studio Options page from the Tools –> Options menu. Then select the tree node labeled “Debugging”. At the right panel, find for the settings that says “Use the legacy C# and VB expression evaluators” and check it as shown below:


Solution - Internal error in the expression evaluator - Visual Studio 2015


Click “OK” to save the options/settings of Visual Studio. Run the debugger once again. Now you will be able to debug and watch any variable inside your IDE. I hope that the post was useful and helped you to resolve it. Don’t just stop here, read out my other posts on Windows 10 Tips & Tricks series and Visual Studio 2015 Tips & Tricks. Till the time I publish a new blog post, happy coding!!!


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