using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

public class VideoWork
{
    private const int WM_USER = 0x400;
    private const int WS_CHILD = 0x40000000;
    private const int WS_VISIBLE = 0x10000000;
    private const int WM_CAP_START = WM_USER;
    private const int WM_CAP_STOP = WM_CAP_START + 68;
    private const int WM_CAP_DRIVER_CONNECT = WM_CAP_START + 10;
    private const int WM_CAP_DRIVER_DISCONNECT = WM_CAP_START + 11;
    private const int WM_CAP_SAVEDIB = WM_CAP_START + 25;
    private const int WM_CAP_GRAB_FRAME = WM_CAP_START + 60;
    private const int WM_CAP_SEQUENCE = WM_CAP_START + 62;
    private const int WM_CAP_FILE_SET_CAPTURE_FILEA = WM_CAP_START + 20;
    private const int WM_CAP_SEQUENCE_NOFILE = WM_CAP_START + 63;
    private const int WM_CAP_SET_OVERLAY = WM_CAP_START + 51;
    private const int WM_CAP_SET_PREVIEW = WM_CAP_START + 50;
    private const int WM_CAP_SET_CALLBACK_VIDEOSTREAM = WM_CAP_START + 6;
    private const int WM_CAP_SET_CALLBACK_ERROR = WM_CAP_START + 2;
    private const int WM_CAP_SET_CALLBACK_STATUSA = WM_CAP_START + 3;
    private const int WM_CAP_SET_CALLBACK_FRAME = WM_CAP_START + 5;
    private const int WM_CAP_SET_SCALE = WM_CAP_START + 53;
    private const int WM_CAP_SET_PREVIEWRATE = WM_CAP_START + 52;
    private IntPtr hWndC;
    private bool bWorkStart = false;
    private IntPtr mControlPtr;
    private int mWidth;
    private int mHeight;
    private int mLeft;
    private int mTop;


    /**/
    ///   <summary> 
    ///   初始化显示图像 
    ///   </summary> 
    ///   <param   name= "handle "> 控件的句柄 </param> 
    ///   <param   name= "left "> 开始显示的左边距 </param> 
    ///   <param   name= "top "> 开始显示的上边距 </param> 
    ///   <param   name= "width "> 要显示的宽度 </param> 
    ///   <param   name= "height "> 要显示的长度 </param> 
    public VideoWork(IntPtr handle, int left, int top, int width, int height)
    {
        mControlPtr = handle;
        mWidth = width;
        mHeight = height;
        mLeft = left;
        mTop = top;
    }

    [DllImport("avicap32.dll ")]
    private static extern IntPtr capCreateCaptureWindowA(byte[] lpszWindowName, int dwStyle, int x, int y, int nWidth, int nHeight, IntPtr hWndParent, int nID);

    [DllImport("avicap32.dll ")]
    private static extern int capGetVideoFormat(IntPtr hWnd, IntPtr psVideoFormat, int wSize);

    // 
    //这里特别注意，因为WinAPI中的long为32位，而C#中的long为64wei，所以需要将lParam该为int 
    // 
    [DllImport("User32.dll ")]
    private static extern bool SendMessage(IntPtr hWnd, int wMsg, int wParam, int lParam);

    /**/
    ///   <summary> 
    ///   开始显示图像 
    ///   </summary> 
    public void Start()
    {
        if (bWorkStart)
            return;

        bWorkStart = true;
        byte[] lpszName = new byte[100];

        hWndC = capCreateCaptureWindowA(lpszName, WS_CHILD | WS_VISIBLE, mLeft, mTop, mWidth, mHeight, mControlPtr, 0);

        if (hWndC.ToInt32() != 0)
        {
            SendMessage(hWndC, WM_CAP_SET_CALLBACK_VIDEOSTREAM, 0, 0);
            SendMessage(hWndC, WM_CAP_SET_CALLBACK_ERROR, 0, 0);
            SendMessage(hWndC, WM_CAP_SET_CALLBACK_STATUSA, 0, 0);
            SendMessage(hWndC, WM_CAP_DRIVER_CONNECT, 0, 0);
            SendMessage(hWndC, WM_CAP_SET_SCALE, 1, 0);
            SendMessage(hWndC, WM_CAP_SET_PREVIEWRATE, 66, 0);
            SendMessage(hWndC, WM_CAP_SET_OVERLAY, 1, 0);
            SendMessage(hWndC, WM_CAP_SET_PREVIEW, 1, 0);
            //Global.log.Write( "SendMessage "); 
        }
        return;

    }
    /**/
    ///   <summary> 
    ///   停止显示 
    ///   </summary> 
    public void Stop()
    {
        SendMessage(hWndC, WM_CAP_DRIVER_DISCONNECT, 0, 0);
        bWorkStart = false;
    }

    /**/
    ///   <summary> 
    ///   抓图 
    ///   </summary> 
    ///   <param   name= "path "> 要保存bmp文件的路径 </param> 
    public void GrabImage(string path)
    {
        IntPtr hBmp = Marshal.StringToHGlobalAnsi(path);
        SendMessage(hWndC, WM_CAP_SAVEDIB, 0, hBmp.ToInt32());
    }
}

调用方法：

在窗体上拖入一个panel

调用代码为：

VideoWork wv = new VideoWork(panel1.Handle, 0, 0, panel1.Width, panel1.Height);
wv.Start();