1
// obj是一个Button转换为object类型的按钮
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// 那么, (obj as Button).Text = "新的文本"; 是可用的, 它将为控件指定一个新的文本
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(obj as Button).Text = "新的文本";
4
// 注意, as运算符的优先级低于.运算符, 所以括号不可以省去

1
bool Moving = false;                // 标识是否在拖动控件
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Point MouseFirstLocation;           // 鼠标按下时, 相对于控件的坐标
3

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private void ExempleButton_MouseDown(object sender, MouseEventArgs e)
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{
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    Moving = true;                                                   // 表示进入拖动控件的状态
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    Point MousePoint = Control.MousePosition;                        // 获取鼠标相对屏幕的坐标
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    MouseFirstLocation = ExempleButton.PointToClient(MousePoint);    // 获取坐标相对于控件的相对坐标并赋值给MouseFirstLocation
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}
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private void ExempleButton_MouseMove(object sender, MouseEventArgs e)
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{
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    if (Moving)
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    {
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        Point MousePoint = Control.MousePosition;                                                                                                   // 获取鼠标相对屏幕的坐标
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        Point MousePointToContainer = ExempleButton.Parent.PointToClient(MousePoint);                                                               // 获取鼠标相对控件父容器的坐标
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        Point ControlNewLocation = new Point(MousePointToContainer.X - MouseFirstLocation.X, MousePointToContainer.Y - MouseFirstLocation.Y);       // 计算控件应处于的, 新的坐标
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        ExempleButton.Location = ControlNewLocation;                                                                                                // 移动控件
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    }
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}
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private void ExempleButton_MouseUp(object sender, MouseEventArgs e)
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{
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    Moving = false;                                                  // 脱离拖动控件的状态
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}

1
class DragMove
2
{
3
    public DragMove(MouseButtons MouseButton)
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    {
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        this.MouseButton = MouseButton;
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    }
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    public DragMove()
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    {
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        AllMouseButton = true;
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    }
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    object AboutControl;                                  // 表示当前移动控件操作是针对哪个控件的
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    bool Moving = false;                                  // 表示是否正在移动控件
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    bool AllMouseButton = false;                          // 表示是否处理所有按钮
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    Point ControlStartLocation;                           // 表示移动操作时, 控件的初始位置
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    Point MouseFirstLocationAboutParent;                  // 表示移动操作时, 鼠标的初始位置
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    MouseButtons MouseButton;
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    List<Control> AddedControls = new List<Control>();
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    void MouseDownEvent(object sender, MouseEventArgs e)
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    {
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        if ((e.Button == MouseButton) || AllMouseButton)
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        {
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            AboutControl = sender;
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            Moving = true;
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            ControlStartLocation = (sender as Control).Location;
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            if (sender is Form)
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            {
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                MouseFirstLocationAboutParent = Control.MousePosition;
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            }
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            else
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            {
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                MouseFirstLocationAboutParent = (sender as Control).Parent.PointToClient(Control.MousePosition);
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            }
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        }
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    }
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    void MouseMoveEvent(object sender, MouseEventArgs e)
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    {
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        if (sender == AboutControl)
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        {
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            if (Moving)
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            {
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                Point MouseLocationNow;
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                if (sender is Form)
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                {
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                    MouseLocationNow = Control.MousePosition;
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                }
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                else
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                {
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                    MouseLocationNow = (sender as Control).Parent.PointToClient(Control.MousePosition);
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                }
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                Point ControlNewLocation = new Point(MouseLocationNow.X - MouseFirstLocationAboutParent.X + ControlStartLocation.X, MouseLocationNow.Y - MouseFirstLocationAboutParent.Y + ControlStartLocation.Y);
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                (sender as Control).Location = ControlNewLocation;
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            }
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        }
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        else
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        {
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            if (Moving)
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            {
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                Moving = false;
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                (AboutControl as Control).Location = ControlStartLocation;
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            }
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        }
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    }
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    void MouseUpEvent(object sender, MouseEventArgs e)
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    {
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        if (sender != AboutControl)
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        {
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            if (Moving)
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            {
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                (AboutControl as Control).Location = ControlStartLocation;
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            }
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        }
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        Moving = false;
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    }
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    public bool AddControl(Control control)
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    {
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        if (AddedControls.Contains(control))
79
        {
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            return false;
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        }
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        else
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        {
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            control.MouseDown += MouseDownEvent;
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            control.MouseMove += MouseMoveEvent;
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            control.MouseUp += MouseUpEvent;
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            AddedControls.Add(control);
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            return true;
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        }
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    }
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    public bool RemoveControl(Control control)
92
    {
93
        if (AddedControls.Contains(control))
94
        {
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            control.MouseDown -= MouseDownEvent;
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            control.MouseMove -= MouseMoveEvent;
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            control.MouseUp -= MouseUpEvent;
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            AddedControls.Remove(control);
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            return true;
100
        }
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        else
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        {
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            return false;
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        }
105
    }
106
}