PtrToStructure() generates SafeArrayTypeMismatchException

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Folks,

Please help me chase out a SafeArrayTypeMismatchException that I keep getting. I need to pass a struct to unmanaged DLL. One of the struct members is a variable-length array. Unmanaged code will populate it with data, then my C# code will use the data.

Approach:
1. Get IntPtr for my structure using StructureToPtr(), do the memory allocation too, of course.
2. Call unmanaged function, and pass IntPtr as a parameter
3. Get the populated structure using PtrToStructure()

If for the purposes of an exercise I call StructureToPtr() and PtrToStructure() back-to-back there are no exceptions.

PtrToStructure() generates SafeArrayTypeMismatchException, if I put a call to unmanaged DLL between StructureToPtr() and PtrToStructure(). The description for SafeArrayTypeMismatchException is "Mismatch has occurred between the runtime type of the array and the sub type recorded in the metadata."

Any suggestion, insight or reference is really appreciated!

I can post my code if needed.

- Nick

Posted 27-Dec-10 14:03pm

Nick Alexeev

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Sergey Alexandrovich Kryukov 27-Dec-10 20:44pm

Needs code sample on .NET (C#) side as well as on native side; at least definition of types and method profile

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Espen Harlinn · Accepted Answer · 2010-12-28T04:16:00

Have you made sure that your struct is suitable for interop using appropriate attributes from the System.Runtime.InteropServices namespace?

Here is one example:

XML

[StructLayout( LayoutKind.Sequential, CharSet = CharSet.Unicode )]
    public struct OSVERSIONINFO
    {
        internal int dwOSVersionInfoSize;
        /// <summary>
        /// Major
        /// </summary>
        public int dwMajorVersion;
        /// <summary>
        /// Minor
        /// </summary>
        public int dwMinorVersion;
        /// <summary>
        /// Build
        /// </summary>
        public int dwBuildNumber;
        /// <summary>
        /// Platform type
        /// </summary>
        public PlatformType dwPlatformId;
        /// <summary>
        /// Null-terminated string that provides arbitrary 
        /// additional information about the OS.
        /// </summary>
        [MarshalAs( UnmanagedType.ByValTStr, SizeConst = 256 )]
        public string szCSDVersion;
    }

regards
Espen Harlinn