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You have a Microsoft Visual C++ .NET 2003 application that uses multiple application domains. When you try to call managed code from unmanaged code in a DLL that has already been loaded in another application domain, you may receive the following error message:
An unhandled exception of type 'System.NullReferenceException' occurred in mscorlib.dll Additional information: Object reference not set to an instance of an object.
Note In some scenarios, you may receive one of the following error messages:
You may notice this problem if your application contains unmanaged code and uses multiple application domains.
For example, if you have an application that uses multiple application domains that use a set of DLLs, you can successfully load and use these DLLs in the first application domain. However, when you try to call the managed code in one of these DLLs from unmanaged code in a different (second) application domain, the behavior that is mentioned in the "Symptoms" section of this article occurs. The application does not load the managed code in the second application domain because the code has already been loaded in another application domain that is in the same process.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section of this article.
For more information, visit the following Microsoft Developer Network (MSDN) Web sites: