VS 2017 immediate window shows "Internal error in the C# compiler"

c# debugging visual-studio-2017 visual-studio-debugging immediate-window
Thaoden picture Thaoden · Apr 26, 2018 · Viewed 8.4k times · Source

I use Visual Studio 2017 (15.6.6). When debugging, I try to evaluate simple expressions like int a = 2; in the immediate window. An error

Internal error in the C# compiler

is thrown.

I tried to enable Use Managed Compatibility Mode as hinted at in this question but it didn't help.

Thanks for any help.

Answer

Thaoden picture Thaoden · Apr 26, 2018

Searching further I found this issue on GitHub where an answer recommends to also check Use the legacy C# and VB expression evaluators. Visual Studio gives me a warning about checking this option, but turning this on I can evaluate expressions in the immediate window again.

It is even possible to turn off the Use Managed Compatibility Mode again.

Update: Notice though that using the legacy expression evaluators prevents me from inspecting local variables at debug time, so I wouldn't call it a solution.

Related questions

How do I remedy "The breakpoint will not currently be hit. No symbols have been loaded for this document." warning?

A C# desktop application on the express edition worked, but then it didn't work 5 seconds later. I tried the following: Ensure debug configuration, debug flag, and full debug information are set on all assemblies. Delete all bin and obj folders …

Read More
Writing to output window of Visual Studio

I am trying to write a message to the output window for debugging purposes. I searched for a function like Java's system.out.println(""). I tried Debug.Write, Console.Write, and Trace.Write. It does not give an error, but …

Read More
The breakpoint will not currently be hit. No symbols have been loaded for this document in a Silverlight application

Ok, what I have: Visual Studio 2010 RC, W7 x64, started a new project type of Silverlight application. Hosting the Silverlight application in a ASP.NET Web Application Project. Silverlight Version 3.0. Added a LinqToSQL Class, a WCF Service, a Winform Tester …

Read More