无边框窗体的拖动和拉伸

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
        }

        protected override void OnMouseDown(MouseEventArgs e)
        {
            base.OnMouseDown(e);
            if (e.Button == MouseButtons.Left &&
                this.WindowState != FormWindowState.Maximized)
            {
                ReleaseCapture();
                SendMessage(this.Handle, 274, 61440 + 9, 0);
            }
        }

        [DllImport("user32.dll")]
        public static extern int ReleaseCapture();

        [DllImport("user32.dll")]
        public static extern int SendMessage(IntPtr hwnd, int msg, int up, int lp);

        protected override void WndProc(ref Message m)
        {
            switch (m.Msg)
            {
                case (int)WindowsMessage.WM_NCHITTEST:
                    this.WM_NCHITTEST(ref m);
                    break;
                default:
                    base.WndProc(ref m);
                    break;
            }
        }

        public static int LOWORD(int value)
        {
            return value & 0xFFFF;
        }

        public static int HIWORD(int value)
        {
            return value >> 16;
        }

        private void WM_NCHITTEST(ref Message m)
        {
            int wparam = m.LParam.ToInt32();
            Point point = new Point(LOWORD(wparam), HIWORD(wparam));
            point = this.PointToClient(point);

            if (point.X <= 5)
            {
                if (point.Y <= 5)
                    m.Result = (IntPtr)WinAPIConst.HTTOPLEFT;
                else if (point.Y > this.Height - 5)
                    m.Result = (IntPtr)WinAPIConst.HTBOTTOMLEFT;
                else
                    m.Result = (IntPtr)WinAPIConst.HTLEFT;
            }
            else if (point.X >= this.Width - 5)
            {
                if (point.Y <= 5)
                    m.Result = (IntPtr)WinAPIConst.HTTOPRIGHT;
                else if (point.Y >= this.Height - 5)
                    m.Result = (IntPtr)WinAPIConst.HTBOTTOMRIGHT;
                else
                    m.Result = (IntPtr)WinAPIConst.HTRIGHT;
            }
            else if (point.Y <= 5)
            {
                m.Result = (IntPtr)WinAPIConst.HTTOP;
            }
            else if (point.Y >= this.Height - 5)
            {
                m.Result = (IntPtr)WinAPIConst.HTBOTTOM;
            }
            else
                base.WndProc(ref m);
        }
    }

    public enum WindowsMessage
    {
        /// <summary>
        /// 移动鼠标，桉树或释放鼠标时发生
        /// </summary>
        WM_NCHITTEST = 0x84,
    }
    public class WinAPIConst
    {
        public const int HTLEFT = 10;
        public const int HTRIGHT = 11;
        public const int HTTOP = 12;
        public const int HTTOPLEFT = 13;
        public const int HTTOPRIGHT = 14;
        public const int HTBOTTOM = 15;
        public const int HTBOTTOMLEFT = 0x10;//16
        public const int HTBOTTOMRIGHT = 17;
        public const int HTCAPTION = 2;

    }
}