'System.AccessViolationException' :Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

[Chandrashekhar C]

Our application is calling a VC++ 6.0 (MFC Automation server) dll from a sample VB.Net (VS 2017 frame work 4.7.2), while calling a method from .Net it is throwing the below error message.

The same functionality is working fine from VB6 application, it is happening only when calling from a .Net 4.7.2 executable.

'System.AccessViolationException' in mscorlib.dll

Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.”

VB.Net code

Dim obj As New MFCDLL.MFCclass

Dim obj1 As object


obj1 = obj.GetNextMethodRef()

VC++ 6.0 MFCDLL (MFC/ATL automation server) code

LPDISPATCH MFCClass::GetNextMethodRef

{

//returns an IDispatch pointer to the Class Object

//

try

{

return ClassMethod1()->GetIDispatch(TRUE); “Access Violation Error is thrown here”

}

Catch (ErrorClass* pe)

{

Exception;

}

Declaration of m_PointertoMFCClass2

MFCClass2* m_PointertoMFCClass2;


MFCClass2* MFCClass:: ClassMethod1()

{

//returns a pointer to the portfolio object

//

try

{

return m_PointertoMFCClass2;

}


Catch (ErrorClass * pe)

{

Exception;

}

Whereas other methods and functions of this DLL which are not using GetIDispatch methods are working fine.


Please let us know if any limitation is there of using VC ++ 6 (MFC) dll with .Net. Also, do let us know resolution of this issue.

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