如何从C＃将窗口句柄传递给C ++ Win32 dll

Question

I have one project which capture images from multiple cameras which is in C++ .I want to use that project in my new project which is in C#.I had made dll of that project.My question is ,how can i use that dll in my project.I know by passing window handle to C++ dll we can use it but i dont know how to do it and what changes should i make in dll.

Please forgive ,if it is foolish question.

Answer 1

I had the exact problem as you and this article helped me. http://blogs.msdn.com/b/jonathanswift/archive/2006/10/03/dynamically-calling-an-unmanaged-dll-from-.net-_2800_c_23002900_.aspx

To pass the handle, you can add another function in C++ end. Something like,

(in the header)
extern "C" __declspec(dllexport) void SetParent(HWND hWnd);

To use the SetParent in C#

 class Program
 {
    ...

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate void SetParent(IntPtr hWnd);

    public void testMethod()
    {
           ...
           IntPtr getAddress = NativeMethods.GetProcAddress(pDll, "SetParent");
           ...
           SetParent setParent = (SetParent)Marshal.GetDelegateForFunctionPointer(getAddress, typeof(SetParent));
           setParent(this.Handle);
           ...       
    }
 } 

Answer 2

If your C++ project is already in a DLL you can call any functions that it exports using P/Invoke . You will have to declare the method in your C# assembly as shown below, but then you can call it like a standard static method.

[DllImport("YourDllsName.dll")]
public static extern bool FunctionThatAWindowHandleAndReturnsBool(IntPtr hWnd);

Depending on the types of parameters that your C++ DLL's functions take the marshaling of the .Net datatypes to C data types can get complicated.