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.NET Forum / .NET Framework / Interop / October 2005IntPtr marshal causes exception
I am writing a C++ program that is using a C# control. It calls a function that requires a handle to data in memory. If I set up the C# function to take this parameter as a uint, it works fine. I would rather set up the parameter as an IntPtr. But when I do that, I get an exception when the C++ program calls the function. Any idea why the exception occurs? Thanks! C++ Code: HANDLE MyData = GlobalAlloc(GMEM_MOVEABLE,File.GetLength()); LPVOID Mem = GlobalLock(MyData); [... populate data ...] GlobalUnlock(MyData); MyControl->MyFunction((long)Data); GlobalFree(MyData); C# Interface Function: bool MyFunction(IntPtr hData); > I am writing a C++ program that is using a C# control. It calls a > function that requires a handle to data in memory. If I set up the C# > function to take this parameter as a uint, it works fine. I would > rather set up the parameter as an IntPtr. But when I do that, I get an > exception when the C++ program calls the function. What kind of exception? What is your C# method doing with the IntPtr? Rob I am not sure what the exception is because I am having some difficulty trapping it. I will try again. What my C# method does with the IntPtr seems to be irrelevant. The exception is occurring somewhere after the call in C++ and before my C# function gets it. > > I am writing a C++ program that is using a C# control. It calls a > > function that requires a handle to data in memory. If I set up the C# [quoted text clipped - 5 lines] > > Rob I am not sure what the exception is because I am having some difficulty trapping it. I will try again. What my C# method does with the IntPtr seems to be irrelevant. The exception is occurring somewhere after the call in C++ and before my C# function gets it. > > I am writing a C++ program that is using a C# control. It calls a > > function that requires a handle to data in memory. If I set up the C# [quoted text clipped - 5 lines] > > Rob The general message I get in the exception is: "An unhandled exception of type 'System.Runtime.InteropServices.SEHException' occurred in HOST.exe Additional information: External component has thrown an exception" > > I am writing a C++ program that is using a C# control. It calls a > > function that requires a handle to data in memory. If I set up the C# [quoted text clipped - 5 lines] > > Rob In C#, the memory is managed by GC, so the memory address is not fixed. >I am writing a C++ program that is using a C# control. It calls a > function that requires a handle to data in memory. If I set up the C# [quoted text clipped - 16 lines] > C# Interface Function: > bool MyFunction(IntPtr hData); Thanks for the response, but I don't see how that is relevant here. Perhaps you can elaborate? I am not passing around pointers or anything like that. I am passing a handle to memory. Also, I don't get a chance to do anything with the value passed to me. The exception occurs somewhere between my C++ program and my C# program. > In C#, the memory is managed by GC, so the memory address is not fixed. > [quoted text clipped - 18 lines] > > C# Interface Function: > > bool MyFunction(IntPtr hData);
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