没什么好说的了，我把代码都贴出来，大家自己看吧！
webcam类的代码： 
using System;
using System.Runtime.InteropServices;

namespace webcam
{
    /**////
    /// avicap 的摘要说明。
    ///
    public class showVideo
    {
        // showVideo calls
        [DllImport("avicap32.dll")] public static extern IntPtr capCreateCaptureWindowA(byte[] lpszWindowName, int dwStyle, int x, int y, int nWidth, int nHeight, IntPtr hWndParent, int nID);
        [DllImport("avicap32.dll")] public static extern bool capGetDriverDescriptionA(short wDriver, byte[] lpszName, int cbName, byte[] lpszVer, int cbVer);
        [DllImport("User32.dll")] public static extern bool SendMessage(IntPtr hWnd, int wMsg, bool wParam, int lParam);
        [DllImport("User32.dll")] public static extern bool SendMessage(IntPtr hWnd, int wMsg, short wParam, int lParam);
        [DllImport("User32.dll")] public static extern bool SendMessage(IntPtr hWnd, int wMsg, short wParam, FrameEventHandler lParam);
        [DllImport("User32.dll")] public static extern bool SendMessage(IntPtr hWnd, int wMsg, int wParam, ref BITMAPINFO lParam);
        [DllImport("User32.dll")] public static extern int SetWindowPos(IntPtr hWnd, int hWndInsertAfter, int x, int y, int cx, int cy, int wFlags);
        [DllImport("avicap32.dll")]public static extern int capGetVideoFormat(IntPtr hWnd, IntPtr psVideoFormat, int wSize );

        // Constants
        public const int WM_USER = 0x400;
        public const int WS_CHILD = 0x40000000;
        public const int WS_VISIBLE = 0x10000000;
        public const int SWP_NOMOVE = 0x2;
        public const int SWP_NOZORDER = 0x4;
        public const int WM_CAP_DRIVER_CONNECT = WM_USER + 10;
        public const int WM_CAP_DRIVER_DISCONNECT = WM_USER + 11;
        public const int WM_CAP_SET_CALLBACK_FRAME = WM_USER + 5;
        public const int WM_CAP_SET_PREVIEW = WM_USER + 50;
        public const int WM_CAP_SET_PREVIEWRATE = WM_USER + 52;
        public const int WM_CAP_SET_VIDEOFORMAT = WM_USER + 45;
 
        // Structures
        [StructLayout(LayoutKind.Sequential)] public struct VIDEOHDR
        {
            [MarshalAs(UnmanagedType.I4)] public int lpData;
            [MarshalAs(UnmanagedType.I4)] public int dwBufferLength;
            [MarshalAs(UnmanagedType.I4)] public int dwBytesUsed;
            [MarshalAs(UnmanagedType.I4)] public int dwTimeCaptured;
            [MarshalAs(UnmanagedType.I4)] public int dwUser;
            [MarshalAs(UnmanagedType.I4)] public int dwFlags;
            [Mars