FatalExecutionEngineError occurs when you do COM calls together with multiple AppDomains

This article helps you resolve the problem where a FatalExecutionEngineError error might be thrown when you do Component Object Model (COM) calls together with multiple AppDomains.

Original product version:   .NET Framework 4.5
Original KB number:   2997900


In an ASP.NET application, when you create multiple AppDomains and start a method with an optional parameter by using IDispatch::Invoke without specifying a value for the optional parameter, the application may crash and you receive the following error message:

Managed Debugging Assistant FatalExecutionEngineError has detected a problem in xxx.exe. Additional information: The runtime has encountered a fatal error. The address of the error was at 0x0e888517, on thread 0x20a8. The error code is 0xc0000005.


.NET creates an internal GC handle in the first AppDomain where the method call is made and will reuse the same internal GC handle throughout the lifetime of the application regardless of which AppDomain is used. It may cause an application crash if this AppDomain is unloaded.


To work around this issue, implement the changes shared as the code example:

public interface ITestInterface

To do it, follow these steps:

  1. Apply assembly-level IDispatchImplAttribute(IDispatchImplType.CompatibleImpl) to use an operating system provided ITypeInfo implementation instead of .NET's implementation:


    Or, you can apply such attribute on any types that have to be accessed through IDispatch.

  2. Change the interface type to be InterfaceIsDual, as the operating system provided ITypeInfo implementation doesn't support pure dispatch interfaces.

  3. Make the interface public and visible to COM so that the interface actually shows in the type lib, and the corresponding typeinfo can be found in the type lib.