在Winform窗体中通过鼠标拖动，改变控件的位置。在拖动过程中，跟随鼠标显示一个与被拖动控件大小一样的黑框，用以模拟拖动效果。如下图：
以下是源代码。这里拖动了一个Button控件。如果需要，还可以在拖动时改变光标。
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private Control control;
private void Form1_Load(object sender, EventArgs e)
{
this.Paint += new System.Windows.Forms.PaintEventHandler(this.FormDrag_Paint);
control = new Button();
control.MouseDown += new MouseEventHandler(control_MouseDown);
control.MouseMove += new MouseEventHandler(control_MouseMove);
control.MouseUp += new MouseEventHandler(control_MouseUp);
this.Controls.Add(control);
}
//鼠标按下坐标（control控件的相对坐标）
Point mouseDownPoint = Point.Empty;
//显示拖动效果的矩形
Rectangle rect = Rectangle.Empty;
//是否正在拖拽
bool isDrag = false;
void control_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
mouseDownPoint = e.Location;
//记录控件的大小
rect = control.Bounds;
}
}
void control_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
isDrag = true;
//重新设置rect的位置，跟随鼠标移动
rect.Location = getPointToForm(new Point(e.Location.X - mouseDownPoint.X, e.Location.Y - mouseDownPoint.Y));
this.Refresh();
}
}
void control_MouseUp(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
if (isDrag)
{
isDrag = false;
//移动control到放开鼠标的地方
control.Location = rect.Location;
this.Refresh();
}
reset();
}
}
//重置变量
private void reset()
{
mouseDownPoint = Point.Empty;
rect = Rectangle.Empty;
isDrag = false;
}
//窗体重绘
private void FormDrag_Paint(object sender, PaintEventArgs e)
{
if (rect != Rectangle.Empty)
{
if (isDrag)
{//画一个和Control一样大小的黑框
e.Graphics.DrawRectangle(Pens.Black, rect);
}
else
{
e.Graphics.DrawRectangle(new Pen(this.BackColor), rect);
}
}
}
//把相对与control控件的坐标，转换成相对于窗体的坐标。
private Point getPointToForm(Point p)
{
return this.PointToClient(control.PointToScreen(p));
}
}
}