calling C API from C#

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Hi,

I am trying to call C API in .lib file from C#. Pls let me know whether this can be done.

following is the code snippet for C Lib.

XML

#include "stdafx.h"

#include <stdio.h>

void print(const char *message)
{
       printf("%s\\n", message);
}

I am calling this function from c# but it is crashing

C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace CSharp_CLib
{
    class Class1
    {
        [DllImport("C_API_APP.lib", EntryPoint = "print")]

        static extern void print(string message);

        public static void Main(string[] args)
        {

            print("Hello World C# => C++");
        }
    }
}

Posted 21-Aug-13 7:15am

SNI

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joshrduncan2012 21-Aug-13 13:24pm

Why are you mixing languages?

SNI 21-Aug-13 13:35pm

I have libs in C which I used it with MFC (VS2010) application. But due to some limitation in MFC I want to check whether I can use these C APIs from C# so I do not need to convert these libs into dll and then use as an interop. pls suggest.....

2 solutions

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CPallini · Accepted Answer · 2013-08-21T07:32:00

Solution 1

You cannot call functions of a static library, you have to create a dynamic library (DLL) for the purpose.
See, for instance "Using C++ Static Libraries in C#" at CodeGuru[^].

Posted 21-Aug-13 7:32am

CPallini

Comments

Sergey Alexandrovich Kryukov 21-Aug-13 14:43pm

Agree, a 5. I added detail about two options: using P/Invoke or C++/CLI, please see my answer.
—SA

fjdiewornncalwe 21-Aug-13 16:57pm

Absolutely +5.

CPallini 21-Aug-13 17:29pm

Thank you.

Sergey Alexandrovich Kryukov · Accepted Answer · 2013-08-21T08:38:00

You really need to create a C DLL and use it via P/Invoke: http://en.wikipedia.org/wiki/P/Invoke[^].

Please see: http://msdn.microsoft.com/library/en-us/vcmxspec/html/vcmg_PlatformInvocationServices.asp[^].

This CodeProject article will also be useful: http://www.codeproject.com/csharp/EssentialPInvoke.asp[^].

Another option is using, instead of C, not even C++, but C++/CLI. Usually, you can put your C code in such project. The project should be mixed-mode: managed+unmanaged. This way, you can use C code but wrap it in some C++/CLI "ref" types to expose them as you usually do in a regular .NET assembly. Then you can reference this assembly in any .NET project. Please see:
http://en.wikipedia.org/wiki/C%2B%2B/CLI[^],
http://www.ecma-international.org/publications/standards/Ecma-372.htm[^],
http://www.gotw.ca/publications/C++CLIRationale.pdf[^],
http://msdn.microsoft.com/en-us/library/xey702bw.aspx[^].

—SA