Loading a 32-bit dll in a 64-bit process [duplicat

Question

This question already has an answer here:

• Target 32 Bit or 64 Bit native DLL depending on environment 3 answers
• DllImport - An attempt was made to load a program with an incorrect format [duplicate] 1 answer

I want my C# application to conditionally run a native method, conditionally choosing to run either the x86 or the x64 version of the dll. Whenever I try to load the 32 bit dll I get the below error:

Unhandled Exception: System.BadImageFormatException: An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B)
   at <exeName>.MiniDumpMethods.MiniDumpWriteDumpX86(IntPtr hProcess, UInt32 processId, SafeHandle hFile, MINIDUMP_TYPE dumpType, IntPtr expParam, IntPtr userStreamParam, IntPtr callbackParam)

Background context: I want my binary to take a memory dump of a given process. Based on whether or not the process it's taking a memory dump of is 32 or 64 bit it'll choose to run the MiniDumpwriteDump method from the x86 or x64 version of dbghelp.dll.

I'm currently doing the following:

[SuppressUnmanagedCodeSecurity]
internal static class MiniDumpMethods
{
    [DllImport("dbghelp.dll",
        EntryPoint = "MiniDumpWriteDump",
        CallingConvention = CallingConvention.StdCall,
        CharSet = CharSet.Unicode,
        ExactSpelling = true,
        SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool MiniDumpWriteDump(
        IntPtr hProcess,
        uint processId,
        SafeHandle hFile,
        MINIDUMP_TYPE dumpType,
        IntPtr expParam,
        IntPtr userStreamParam,
        IntPtr callbackParam);

[DllImport("dbghelpx86.dll",
EntryPoint = "MiniDumpWriteDump",
CallingConvention = CallingConvention.StdCall,
CharSet = CharSet.Unicode,
ExactSpelling = true,
SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool MiniDumpWriteDumpX86(
        IntPtr hProcess,
        uint processId,
        SafeHandle hFile,
        MINIDUMP_TYPE dumpType,
        IntPtr expParam,
        IntPtr userStreamParam,
        IntPtr callbackParam);
}

Any idea how I can conditionally load either the x86 or the x64 version of the dll?

(Note: dbghelpx86.dll is the x86 version of dbghelp.dll that I renamed)

Thanks

Answer 1

You cannot load a 32 bit DLL into a 64 bit process. To support this you will have to have two different EXE's, one compiled as 64 bit and one compiled as 32 bit.

If you run the 64 bit process and encounter a 32 bit dump, you'll have to launch the 32 bit version of the EXE to process the dump file. Once it is processed you can use some sort of IPC (Interprocess Communication) mechanism to send the results back to the 64 bit process.