How to pass strings from C# to C++ (and from C++ to C#) using DLLImport?

Question

I\'ve been trying to send a string to/from C# to/from C++ for a long time but didn\'t manage to get it working yet ...

So my question is simple :
Does anyone kno

Answer 1

A lot of functions that are encountered in the Windows API take string or string-type parameters. The problem with using the string data type for these parameters is that the string datatype in .NET is immutable once created so the StringBuilder datatype is the right choice here. For an example examine the API function GetTempPath()

Windows API definition

DWORD WINAPI GetTempPath(
  __in   DWORD nBufferLength,
  __out  LPTSTR lpBuffer
);

.NET prototype

[DllImport("kernel32.dll")]
public static extern uint GetTempPath
(
uint nBufferLength, 
StringBuilder lpBuffer
);

Usage

const int maxPathLength = 255;
StringBuilder tempPath = new StringBuilder(maxPathLength);
GetTempPath(maxPathLength, tempPath);