Question

I have a C# winapp. I call a native .dll file (created in C++ by myself) from the C# app, and it works fine.

But when I copy my application (.exe and .dll files) to another machine, I get an error that says:

Unable to load DLL “c:\dllname.dll”: The specified module could not be found. (Exception from HRESULT: 0x8007007E)

Here is the C# code:

class IsoMessageHelper
{
    public const string ISO8583_DLL = "c:\\Hc8583.dll";
    [DllImport(ISO8583_DLL, CallingConvention = CallingConvention.Cdecl)]
    public static extern bool InitializationRq(...)
}

What should I do?

Answer 1

A common issue when deploying .Net applications that have native dependencies, is that the native dlls may be missing dependencies themselves on the target machines e.g. the correct version of the C runtime.

Use a tool such a Dependency Walker to analyze your native dll and determine if it has a missing dependency on the machine you have copied it too.