Using a Delphi native dll in C# (DllImport issue)

Question

I'm having issues importing a Delphi native dll to .net. I'm getting System.EntryPointNotFoundException.

Here's my delphi dll:

procedure ProcedimientoEncriptar(texto,clave,resultado:PChar); export stdcall;
    var ...
    begin
    ....
    ....
    end;

    exports
      ProcedimientoEncriptar ;

And here's my DllImport on .Net (C#) code:

[DllImport("CryptoDLL.dll", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Auto)]
        public static extern void ProcedimientoEncriptar([MarshalAs(UnmanagedType.LPStr)]string texto, [MarshalAs(UnmanagedType.LPStr)]string clave, [MarshalAs(UnmanagedType.LPStr)] StringBuilder resultado);

Any help would be appreciated, Diego.

That's not your actual code I think. A Delphi function is meant to have a return value. But yours doesn't. And your C# code has void return. Is your Delphi code really function? Isn't it procedure. Your Delphi code in the question doesn't compile. Please use copy/paste when putting code in questions. Don't post fake code. — David Heffernan
– David Heffernan, Commented Sep 27, 2012 at 14:05
You're right, it was procedure but i changed it for testing purposes (i tried returning a PChar). — Diego Iturriaga
– Diego Iturriaga, Commented Sep 27, 2012 at 15:35
I'm not sure, I'm pretty new to Delphi but I'm using Embarcadero's Solution (Borland Developer Studio 2006)... — Diego Iturriaga
– Diego Iturriaga, Commented Sep 27, 2012 at 20:37

David Heffernan · Accepted Answer · 2012-09-27 14:03:10Z

4

The only explanation for System.EntryPointNotFoundException is that the DLL that the C# code is finding is not the DLL produced from the Delphi code that you show. So, perhaps the C# code is picking up an out of date version of the DLL. Or perhaps it's picking up a completely different DLL.

For example, my system has a DLL named cryptdll.dll in the system32 directory. Most likely that's the DLL that your C# code is finding.

In order to make sure that the right DLL is found, you need to place a copy of the Delphi DLL in the same directory as the C# executable file.

answered Sep 27, 2012 at 14:03

David Heffernan

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2 Comments

Diego Iturriaga Over a year ago

Thanks, David, that was the issue. I didn't know that a 'cryptdll.dll' existed on the system. I renamed and copied the dll to the /bin/ directory and it worked (it's an ASP .Net application). Cheers, Diego.

umlcat Over a year ago

@Diego Iturriaga: David is right. In windows, the location of a D.L.L. can be a problem, and is not related to been Delphi generated, in this case, the same error can happen to a D.L.L. compiled in other language, and wrong filesystem location.

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