如何用c#打开摄像头

   const short WM_CAP = 1024;
        const int WM_CAP_DRIVER_CONNECT = WM_CAP + 10;
        const int WM_CAP_DRIVER_DISCONNECT = WM_CAP + 11;
        const int WM_CAP_EDIT_COPY = WM_CAP + 30;
        const int WM_CAP_SET_PREVIEW = WM_CAP + 50;
        const int WM_CAP_SET_PREVIEWRATE = WM_CAP + 52;
        const int WM_CAP_SET_SCALE = WM_CAP + 53;
        const int WS_CHILD = 1073741824;
        const int WS_VISIBLE = 268435456;
        const short SWP_NOMOVE = 2;
        const short SWP_NOSIZE = 1;
        const short SWP_NOZORDER = 4;
        const short HWND_BOTTOM = 1;
        int iDevice = 0;
        int hHwnd;
        [System.Runtime.InteropServices.DllImport("user32", EntryPoint = "SendMessageA")]
        static extern int SendMessage(int hwnd, int wMsg, int wParam, [MarshalAs(UnmanagedType.AsAny)]
            object lParam);
        [System.Runtime.InteropServices.DllImport("user32", EntryPoint = "SetWindowPos")]
        static extern int SetWindowPos(int hwnd, int hWndInsertAfter, int x, int y, int cx, int cy, int wFlags);
        [System.Runtime.InteropServices.DllImport("user32")]
        static extern bool DestroyWindow(int hndw);
        [System.Runtime.InteropServices.DllImport("avicap32.dll")]
        static extern int capCreateCaptureWindowA(string lpszWindowName, int dwStyle, int x, int y, int nWidth, short nHeight, int hWndParent, int nID);
        [System.Runtime.InteropServices.DllImport("avicap32.dll")]
        static extern bool capGetDriverDescriptionA(short wDriver, string lpszName, int cbName, string lpszVer, int cbVer);
        private void OpenPreviewWindow()
        {
            int iHeight = 320;
            int iWidth = 200;
            //
            //  Open Preview window in picturebox
            //
            hHwnd = capCreateCaptureWindowA(iDevice.ToString(), (WS_VISIBLE | WS_CHILD), 0, 0, 640, 480, picCapture.Handle.ToInt32(), 0);
            //
            //  Connect to device
            //
            if (SendMessage(hHwnd, WM_CAP_DRIVER_CONNECT, iDevice, 0) == 1)
            {
                //
                // Set the preview scale
                //
                SendMessage(hHwnd, WM_CAP_SET_SCALE, 1, 0);
                //
                // Set the preview rate in milliseconds
                //
                SendMessage(hHwnd, WM_CAP_SET_PREVIEWRATE, 66, 0);
                //
                // Start previewing the image from the camera
                //
                SendMessage(hHwnd, WM_CAP_SET_PREVIEW, 1, 0);
                //
                //  Resize window to fit in picturebox
                //
                SetWindowPos(hHwnd, HWND_BOTTOM, 0, 0, iWidth, iHeight, (SWP_NOMOVE | SWP_NOZORDER));
            }
            else
            {
                //
                //  Error connecting to device close window
                // 
                DestroyWindow(hHwnd);
            }
        }
        private void ClosePreviewWindow()
        {
            //
            //  Disconnect from device
            //
            SendMessage(hHwnd, WM_CAP_DRIVER_DISCONNECT, iDevice, 0);
            //
            //  close window
            //
            DestroyWindow(hHwnd);
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            iDevice = int.Parse(device_number_textBox.Text);
            OpenPreviewWindow();
        }