从ASP.NET服务器端代码访问网络摄像头api错误

Question

I'm tring to use webcam api with asp.net and C#. I included all the library and references I needed for that.

the original code I'm use was for windows application and I'm trying to convert it to asp.net web application.

I have start capturing button when I click it, it should start capturing but it gives me an error.

the error at this line:

  hHwnd = capCreateCaptureWindowA(iDevice.ToString(), (WS_VISIBLE | WS_CHILD), 0, 0, 640, 480, picCapture.Handle.ToInt32(), 0);  

and the error message is:

Error 1 'System.Web.UI.WebControls.Image' does not contain a definition for 'Handle' and no extension method 'Handle' accepting a first argument of type 'System.Web.UI.WebControls.Image' could be found (are you missing a using directive or an assembly reference?) C:\\Users\\Ali\\Documents\\Visual Studio 2008\\Projects\\Conference\\Conference\\Conference1.aspx.cs 63 117 Conference

Please advice!!

................................................
here is the complete code
...........................................

using System;
using System.Collections;
using System.Drawing;
using System.ComponentModel;
using System.Windows.Forms;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Runtime.InteropServices;
using System.Drawing.Imaging;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.IO;

namespace Conference
{
    public partial class Conference1 : System.Web.UI.Page
    {


        #region WebCam API
        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);
        }
        #endregion
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void btnStart_Click(object sender, EventArgs e)
        {
           int  iDevice = int.Parse(device_number_textBox.Text);
            OpenPreviewWindow();
        }
    }
}

Answer 1

You code cannot possibly work.

The native API is tightly tied to standard Windows controls.
It cannot be used in ASP.Net.

Answer 2

只有使用Flash或Silverlight 4才能获得最终用户的网络摄像头。

Answer 3

Among other problems, the image control in ASP.NET corresponds to the <img/> tag in HTML. There is nothing like a window handle associated with an HTML tag.