“Internal error in the expression evaluator”

Question

I\'ve encountered a problem in expression evaluator of visual studio 2015 that says \"Internal error in the expression evaluator\", after some investigations I found that th

Answer 1

In my case I was trying to evaluate lambda expression on List<> and had such error ("Internal error in the expression evaluator"). I was using VS2015, so lambda expressions were allowed. It turns out expression evaluator was lacking of Linq library. I added

using System.Linq;

to my current class and voilà! Lambda evaluated.

Answer 2

I encountered the "internal error in the expression evaluator" error when I was debugging in release mode instead of in debug mode. I had changed it to Release when publishing to production and forgot to change it back to Debug.

Answer 3

That sounds like a bug in the expression evaluator. For a better workaround, instead of checking "Use Managed Compatibility Mode", check "Use the legacy C# and VB expression evaluators". This should enable you to continue using Edit and Continue as well as other features added within the last few releases.

In terms of the "Internal error in expression evaluator", can you please open an issue by going to Help -> Send Feedback -> Report a problem? That will help us fix the problem in future releases.