Internal error in the expression evaluator

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 this is caused by an assembly that is loaded using reflection. This assembly wouldn’t throw any exceptions but after that, vs exp evaluator will fail.
This is not the only assembly that I load, there are some good working ones that don’t influent the evaluator.

To overcome this issue I had to check ‘Menu > options > debugging > Use Managed Compatibility Mode’ but this disables the ‘Edit & Continue’ feature, what can I do?

Properties of the causer assembly:

• its name is the same as the main assembly
  (i changed its name but nothing happened)
• all of my projects are using dotNet 4.5
• all root namespaces are same
  (all of the assemblies are so)

Thanks!

answered Nov 28, 2016 at 21:05

answered Apr 11, 2018 at 12:58

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.

answered Nov 9, 2016 at 14:03

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.

answered Nov 18, 2016 at 18:52

Check your use of the [DebuggerBrowsable] attribute; I found a minimal case in VisualStudio 2017 15.5 and posted it here.

In this particular case, the expression evaluator (EE) crash appears related to the [DebuggerBrowsable] attribute applied to a property overriding a field of the same name. This will account for some percentage of the cases that people are experiencing out there, but there’s no way of knowing how many are due to this specific issue until it gets fixed.

The full and complete demonstration example is shown in the image (and included below for good measure)

Machine-readable copy of the code in the image:

using System;
using System.Diagnostics;

class Program { static void Main() => new _derived(); }

abstract class _base
{
    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    public Object trace;
};

class _derived : _base
{
    public _derived() => Debugger.Break();      // <-- vs2017 EE crash when stopped here

    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    new public Object trace => base.trace;
}

answered Feb 9, 2018 at 3:36

answered May 15, 2018 at 10:51

answered Apr 20, 2022 at 8:04

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 this is caused by an assembly that is loaded using reflection. This assembly wouldn’t throw any exceptions but after that, vs exp evaluator will fail.
This is not the only assembly that I load, there are some good working ones that don’t influent the evaluator.

To overcome this issue I had to check ‘Menu > options > debugging > Use Managed Compatibility Mode’ but this disables the ‘Edit & Continue’ feature, what can I do?

Properties of the causer assembly:

• its name is the same as the main assembly
  (i changed its name but nothing happened)
• all of my projects are using dotNet 4.5
• all root namespaces are same
  (all of the assemblies are so)

Thanks!

answered Nov 28, 2016 at 21:05

answered Apr 11, 2018 at 12:58

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.

answered Nov 9, 2016 at 14:03

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.

answered Nov 18, 2016 at 18:52

Check your use of the [DebuggerBrowsable] attribute; I found a minimal case in VisualStudio 2017 15.5 and posted it here.

In this particular case, the expression evaluator (EE) crash appears related to the [DebuggerBrowsable] attribute applied to a property overriding a field of the same name. This will account for some percentage of the cases that people are experiencing out there, but there’s no way of knowing how many are due to this specific issue until it gets fixed.

The full and complete demonstration example is shown in the image (and included below for good measure)

Machine-readable copy of the code in the image:

using System;
using System.Diagnostics;

class Program { static void Main() => new _derived(); }

abstract class _base
{
    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    public Object trace;
};

class _derived : _base
{
    public _derived() => Debugger.Break();      // <-- vs2017 EE crash when stopped here

    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    new public Object trace => base.trace;
}

answered Feb 9, 2018 at 3:36

answered May 15, 2018 at 10:51

answered Apr 20, 2022 at 8:04