calling C function from C#

[vikrammiddha]

hi,
i have a dll which i made of a C program..
#include <stdio.h>

extern "C"
{

__declspec(dllexport) void DisplayHelloFromDLL(char *input,char *output )
// int n;
{
// char *name = "";
//*name = *input;
printf ("Hello from DLL !\n");

printf ("string is %s", input);
output = input;

}

}


now i need to call this function from the C# code...


using System;
using System.Runtime.InteropServices;

class HelloWorld
{
[DllImport("test1.dll")]
public static extern void DisplayHelloFromDLL(System.String i,System.String o);

static void Main ()
{
Console.WriteLine ("This is C# program");
System.String i = "teststring";
System.String o = "";
DisplayHelloFromDLL (i,o);
Console.WriteLine("output is {0}",o);
}
}

Can anyone tell me how can i pass the string parameter to C function where it is accepting it as char* ... there are 2 variables... one is input and other one is output which i need to get the value back in C#.

[Plater]

The way you are doing it did not work?
You may have to say "ref" in your function declaration.

[DllImport("test1.dll")]
public static extern void DisplayHelloFromDLL(ref String i, ref String o);