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I am getting an occasional System.OverflowException with msg "Overflow" in a .NET call to a VB6 DLL COM server.

The exception seems to be happening somewhere in the transition from COM to .NET:

  • The top of the stack is the COM call itself, at ComClient.VBComClass.ApplicationState()
  • The VB6 ErrorHandler code is not executed, which means that the VB6 function exited normally

Is there a value or condition of a VB6 Long that would overflow a .NET int?

Code snippets:

.NET COM Client:

VBCom comObj = new VBCom();
int appState;
appState = comObj.ApplicationState();

.NET imported COM interface:

[DispId(1610809347)]
int ApplicationState();

VB6 DLL COM Server:

Public Function ApplicationState() As Long
    On Error GoTo ErrorHandler
    ApplicationState = {...call into another VB6 application...}
    Exit Function

    ErrorHandler:
    ApplicationState = -1
    RaiseEvent ErrorHandled("ApplicationState", Err, Error(Err))
End Function
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1 Answer 1

up vote 1 down vote

Have you seen this ?
Troubleshooting Exceptions: System.OverflowException
An OverflowException exception is thrown when an arithmetic, casting, or conversion operation in a checked context results in an overflow. An overflow occurs when an operation produces a value too large for the destination type, infinity, or Not a Number (NaN).

share|improve this answer
    
Yes, I am asking if there is a VB6 Long value or some other condition that could cause this to throw when (I'm assuming) the .NET Interop marshals this as a CLR int. I don't see how since they are the same size. – JMH Jul 16 '12 at 19:23
    
PS If the value inside the VB6 call assigned to ApplicationState was too large, I would have expected the On Error GoTo to be invoked. Instead the VB6 function exits normally and the .NET runtime exception is thrown. – JMH Jul 16 '12 at 19:27

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