C# Dllimport problems in Visual Studio 2010 .NET framework 4

Question

I am trying to import a dll written in C++, in my C# application. The application is supposed to get names of disponible webcams. It works well in .NET framework 3.5 (gets all names properly) but I have problems with getting names in framework 4. I get something like "„îş" instead.

Here are fragments of my code :

• c++ dll :

  TCHAR GetDeviceName(int index)
  {
      char name[255];
      GetDeviceNameAux(index, name);
      TCHAR retVal = (TCHAR)name;
      return retVal;
  }
  

• c# application (that works for framework 3.5)

  [DllImport("FindCaptureDevice.dll")]
  public static extern string GetDeviceName(int index);
  

I have tried also :

[DllImport("FindCaptureDevice.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
    public static extern string GetDeviceName(int index);

with different parameters for CallingConvention ans CharSet.

Thanks in advance for any help.

Answer 1

you can use WIA for capture or scan image

Answer 2

Ok. Thanks to you comments I managed to solve my problem. I used website

and I changed in c# code

[DllImport("FindCaptureDevice.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
    public static extern void GetDeviceName(StringBuilder response, int index);

and I call it with

StringBuilder tempDevice = new StringBuilder(255);
                GetDeviceName(tempDevice, DevCount);

and in c++ code I wrote

void GetDeviceName(char * outChr, int index)
{
    GetDeviceNameAux(index, outChr);
}

and I copy the data to outChr with strcpy_s method.

Answer 3

Change the return type to StringBuilder:

[DllImport("FindCaptureDevice.dll")]
public static extern StringBuilder GetDeviceName(int index);