Incorrect format Exception while trying to call C++ dll from C#

Question

I'm Using C# WPF.
I have a C++ test dll as follow:
.h:

extern "C" __delspec(dllexport) void TestMethod();

.cpp file:

extern "C"
{
    __delspec(dllexport) void TestMethod()
    {
        MessageBox(0, L"Test", L"Test", MB_ICONINFORMATION);
    }
}

C# Code:

[DllImport("DllTest.dll", EntryPoint = "TestMethod")]
public static extern void TestMethod();

And when i'm trying to call to TestMethod i got exception:

an attempt was made to load a program with an incorrect format

What i'm doing wrong?
Thanks!

I have something like [DllImport("DllTest.dll", CallingConvention = CallingConvention.Cdecl)]. Specifying the calling convention helps? — ntohl
– ntohl, Commented Apr 13, 2016 at 8:43

Nitin Purohit · Accepted Answer · 2016-04-13 08:40:38Z

7

This seems to be 32bit/ 64 bit problem. Seems like your C++ dll and C# calling assembly are built for different platform targets. Try compiling both for the same platform (either x86 or x64) and then calling the function.

answered Apr 13, 2016 at 8:40

Nitin Purohit

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3 Comments

Evyatar Over a year ago

Thanks!!!.. i edit my post with another question, if i have more than 1 function, what i need to replace instead [DllImport("DllTest.dll", EntryPoint = "TestMethod")] ?

CompuChip Over a year ago

@Evyatar best post that as a separate question. We prefer a one-question-per-question format :)

Evyatar Over a year ago

@CompuChip, yeah.. i ask a new question :P

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