C# 控件的自定义拖动、改变大小方法

在用VS的窗体设计器时，我们可以发现控件都是可以拖动的，并且还可以调整大小。怎么在自己的程序中可以使用上述功能呢？ 下面的方法值得借鉴！

using System;
using System.Windows.Forms;
using System.Drawing;
namespace ControlSizeChangeEx
{
    /// <summary>
    /// This class implements sizing and moving functions for
    /// runtime editing of graphic controls
    /// </summary>
    public class PickBox
    {
        //////////////////////////////////////////////////////////////////
        // PRIVATE CONSTANTS AND VARIABLES
        //////////////////////////////////////////////////////////////////
        private const int BOX_SIZE = ;
        private Color BOX_COLOR = Color.White;
        private ContainerControl m_container;
        private Control m_control;
        private Label[] lbl = new Label[];
        private int startl;
        private int startt;
        private int startw;
        private int starth;
        private int startx;
        private int starty;
        private bool dragging;
        private Cursor[] arrArrow = new Cursor[] {Cursors.SizeNWSE, Cursors.SizeNS,
   Cursors.SizeNESW, Cursors.SizeWE, Cursors.SizeNWSE, Cursors.SizeNS,
   Cursors.SizeNESW, Cursors.SizeWE};
        private Cursor oldCursor;
        private const int MIN_SIZE = ;
        //
        // Constructor creates 8 sizing handles & wires mouse events
        // to each that implement sizing functions
        //
        public PickBox()
        {
            for (int i = ; i < ; i++)
            {
                lbl[i] = new Label();
                lbl[i].TabIndex = i;
                lbl[i].FlatStyle = ;
                lbl[i].BorderStyle = BorderStyle.FixedSingle;
                lbl[i].BackColor = BOX_COLOR;
                lbl[i].Cursor = arrArrow[i];
                lbl[i].Text = "";
                lbl[i].BringToFront();
                lbl[i].MouseDown += new MouseEventHandler(this.lbl_MouseDown);
                lbl[i].MouseMove += new MouseEventHandler(this.lbl_MouseMove);
                lbl[i].MouseUp += new MouseEventHandler(this.lbl_MouseUp);
            }
        }
        //////////////////////////////////////////////////////////////////
        // PUBLIC METHODS
        //////////////////////////////////////////////////////////////////
        //
        // Wires a Click event handler to the passed Control
        // that attaches a pick box to the control when it is clicked
        //
        public void WireControl(Control ctl)
        {
            ctl.Click += new EventHandler(this.SelectControl);
        }
        /////////////////////////////////////////////////////////////////
        // PRIVATE METHODS
        /////////////////////////////////////////////////////////////////
        //
        // Attaches a pick box to the sender Control
        //
        private void SelectControl(object sender, EventArgs e)
        {
            if (m_control is Control)
            {
                m_control.Cursor = oldCursor;
                //Remove event any pre-existing event handlers appended by this class
                m_control.MouseDown -= new MouseEventHandler(this.ctl_MouseDown);
                m_control.MouseMove -= new MouseEventHandler(this.ctl_MouseMove);
                m_control.MouseUp -= new MouseEventHandler(this.ctl_MouseUp);
                m_control = null;
            }
            m_control = (Control)sender;
            //Add event handlers for moving the selected control around
            m_control.MouseDown += new MouseEventHandler(this.ctl_MouseDown);
            m_control.MouseMove += new MouseEventHandler(this.ctl_MouseMove);
            m_control.MouseUp += new MouseEventHandler(this.ctl_MouseUp);
            //Add sizing handles to Control's <a href="http://lib.csdn.net/base/docker" class='replace_word' title="Docker知识库" target='_blank' style='color:#df3434; font-weight:bold;'>Container</a> (Form or PictureBox)
            for (int i = ; i < ; i++)
            {
                m_control.Parent.Controls.Add(lbl[i]);
                lbl[i].BringToFront();
            }
            //Position sizing handles around Control
            MoveHandles();
            //Display sizing handles
            ShowHandles();
            oldCursor = m_control.Cursor;
            m_control.Cursor = Cursors.SizeAll;
        }
        public void Remove()
        {
            HideHandles();
            m_control.Cursor = oldCursor;
        }
        private void ShowHandles()
        {
            if (m_control != null)
            {
                for (int i = ; i < ; i++)
                {
                    lbl[i].Visible = true;
                }
            }
        }
        private void HideHandles()
        {
            for (int i = ; i < ; i++)
            {
                lbl[i].Visible = false;
            }
        }
        private void MoveHandles()
        {
            int sX = m_control.Left - BOX_SIZE;
            int sY = m_control.Top - BOX_SIZE;
            int sW = m_control.Width + BOX_SIZE;
            int sH = m_control.Height + BOX_SIZE;
            int hB = BOX_SIZE / ;
            int[] arrPosX = new int[] {sX+hB, sX + sW / , sX + sW-hB, sX + sW-hB,
   sX + sW-hB, sX + sW / , sX+hB, sX+hB};
            int[] arrPosY = new int[] {sY+hB, sY+hB, sY+hB, sY + sH / , sY + sH-hB,
   sY + sH-hB, sY + sH-hB, sY + sH / };
            for (int i = ; i < ; i++)
                lbl[i].SetBounds(arrPosX[i], arrPosY[i], BOX_SIZE, BOX_SIZE);
        }
        /////////////////////////////////////////////////////////////////
        // MOUSE EVENTS THAT IMPLEMENT SIZING OF THE PICKED CONTROL
        /////////////////////////////////////////////////////////////////
        //
        // Store control position and size when mouse button pushed over
        // any sizing handle
        //
        private void lbl_MouseDown(object sender, MouseEventArgs e)
        {
            dragging = true;
            startl = m_control.Left;
            startt = m_control.Top;
            startw = m_control.Width;
            starth = m_control.Height;
            HideHandles();
        }
        //
        // Size the picked control in accordance with sizing handle being dragged
        // 0   1   2
        //  7       3
        //  6   5   4
        //
        private void lbl_MouseMove(object sender, MouseEventArgs e)
        {
            int l = m_control.Left;
            int w = m_control.Width;
            int t = m_control.Top;
            int h = m_control.Height;
            if (dragging)
            {
                switch (((Label)sender).TabIndex)
                {
                    case : // Dragging top-left sizing box
                        l = startl + e.X < startl + startw - MIN_SIZE ? startl + e.X : startl + startw - MIN_SIZE;
                        t = startt + e.Y < startt + starth - MIN_SIZE ? startt + e.Y : startt + starth - MIN_SIZE;
                        w = startl + startw - m_control.Left;
                        h = startt + starth - m_control.Top;
                        break;
                    case : // Dragging top-center sizing box
                        t = startt + e.Y < startt + starth - MIN_SIZE ? startt + e.Y : startt + starth - MIN_SIZE;
                        h = startt + starth - m_control.Top;
                        break;
                    case : // Dragging top-right sizing box
                        w = startw + e.X > MIN_SIZE ? startw + e.X : MIN_SIZE;
                        t = startt + e.Y < startt + starth - MIN_SIZE ? startt + e.Y : startt + starth - MIN_SIZE;
                        h = startt + starth - m_control.Top;
                        break;
                    case : // Dragging right-middle sizing box
                        w = startw + e.X > MIN_SIZE ? startw + e.X : MIN_SIZE;
                        break;
                    case : // Dragging right-bottom sizing box
                        w = startw + e.X > MIN_SIZE ? startw + e.X : MIN_SIZE;
                        h = starth + e.Y > MIN_SIZE ? starth + e.Y : MIN_SIZE;
                        break;
                    case : // Dragging center-bottom sizing box
                        h = starth + e.Y > MIN_SIZE ? starth + e.Y : MIN_SIZE;
                        break;
                    case : // Dragging left-bottom sizing box
                        l = startl + e.X < startl + startw - MIN_SIZE ? startl + e.X : startl + startw - MIN_SIZE;
                        w = startl + startw - m_control.Left;
                        h = starth + e.Y > MIN_SIZE ? starth + e.Y : MIN_SIZE;
                        break;
                    case : // Dragging left-middle sizing box
                        l = startl + e.X < startl + startw - MIN_SIZE ? startl + e.X : startl + startw - MIN_SIZE;
                        w = startl + startw - m_control.Left;
                        break;
                }
                l = (l < ) ?  : l;
                t = (t < ) ?  : t;
                m_control.SetBounds(l, t, w, h);
            }
        }
        //
        // Display sizing handles around picked control once sizing has completed
        //
        private void lbl_MouseUp(object sender, MouseEventArgs e)
        {
            dragging = false;
            MoveHandles();
            ShowHandles();
        }
        /////////////////////////////////////////////////////////////////
        // MOUSE EVENTS THAT MOVE THE PICKED CONTROL AROUND THE FORM
        /////////////////////////////////////////////////////////////////
        //
        // Get mouse pointer starting position on mouse down and hide sizing handles
        //
        private void ctl_MouseDown(object sender, MouseEventArgs e)
        {
            dragging = true;
            startx = e.X;
            starty = e.Y;
            HideHandles();
        }
        //
        // Reposition the dragged control
        //
        private void ctl_MouseMove(object sender, MouseEventArgs e)
        {
            if (dragging)
            {
                int l = m_control.Left + e.X - startx;
                int t = m_control.Top + e.Y - starty;
                int w = m_control.Width;
                int h = m_control.Height;
                l = (l < ) ?  : ((l + w > m_control.Parent.ClientRectangle.Width) ?
                  m_control.Parent.ClientRectangle.Width - w : l);
                t = (t < ) ?  : ((t + h > m_control.Parent.ClientRectangle.Height) ?
                m_control.Parent.ClientRectangle.Height - h : t);
                m_control.Left = l;
                m_control.Top = t;
            }
        }
        //
        // Display sizing handles around picked control once dragging has completed
        //
        private void ctl_MouseUp(object sender, MouseEventArgs e)
        {
            dragging = false;
            MoveHandles();
            ShowHandles();
        }
    }
} 

创建一个PickBox对象 ,  调用此对象的WireControl(你希望改变的控件);方法就行了。