C# 如何用鼠标拖出虚线框，释放鼠标虚框消失，就和在windows桌面上拖动鼠标一样

Question

rt，谢谢！

Answer 1

using   System; 
using   System.Collections.Generic; 
using   System.ComponentModel; 
using   System.Data; 
using   System.Drawing; 
using   System.Text; 
using   System.Windows.Forms; namespace   Probation 
{ 
        public   partial   class   frmMain   :   Form 
        { 
                bool   MouseIsDown   =   false; 
                Rectangle   MouseRect   =   Rectangle.Empty;   
                public   frmMain() 
                { 
                        InitializeComponent(); 
                        this.MouseDown+=new   MouseEventHandler(frmMain_MouseDown); 
                        this.MouseMove+=new   MouseEventHandler(frmMain_MouseMove); 
                        this.MouseUp   +=new   MouseEventHandler(frmMain_MouseUp); 
                } 
                void     frmMain_MouseUp(object   sender,   MouseEventArgs   e) 
                { 
                        this.Capture   =   false;   
                        Cursor.Clip   =   Rectangle.Empty;   
                        MouseIsDown   =   false;   
                        DrawRectangle(); 
                        MouseRect   =   Rectangle.Empty; 
                } 
                void     frmMain_MouseMove(object   sender,   MouseEventArgs   e) 
                { 
                        if   (MouseIsDown)   
                              ResizeToRectangle(e.Location);   
                } 
                void     frmMain_MouseDown(object   sender,   MouseEventArgs   e) 
                { 
                        MouseIsDown   =   true; 
                        DrawStart(e.Location);   
                } 
                private   void   ResizeToRectangle(Point   p)   
                {   
                      DrawRectangle();   
                      MouseRect.Width   =   p.X   -   MouseRect.Left;   
                      MouseRect.Height   =   p.Y   -   MouseRect.Top;   
                      DrawRectangle();   
                }   
                private   void   DrawRectangle()   
                {   
                      Rectangle   rect   =   this.RectangleToScreen(MouseRect);   
                      ControlPaint.DrawReversibleFrame(rect,   Color.White,   FrameStyle.Dashed);   
                }   
                private   void   DrawStart(Point   StartPoint)   
                {   
                      this.Capture   =   true; 
                      Cursor.Clip   =   this.RectangleToScreen(new   Rectangle(0,   0,   ClientSize.Width,   ClientSize.Height)); 
                        MouseRect   =   new   Rectangle(StartPoint.X,   StartPoint.Y,   0,   0);   
                }   
        } 
}

Answer 2

命名空间 
using System.Drawing; 定义两个变量 
bool MouseIsDown=false; 
Rectangle MouseRect   =   Rectangle.Empty; 定义三个方法 
private void ResizeToRectangle(Point   p) 
{ 
    DrawRectangle(); 
    MouseRect.Width = p.X - MouseRect.Left; 
    MouseRect.Height = p.Y - MouseRect.Top; 
    DrawRectangle(); 
} 
private void DrawRectangle() 
{ 
   Rectangle rect = this.RectangleToScreen(MouseRect); 
   ControlPaint.DrawReversibleFrame(rect,Color.White,FrameStyle.Dashed); 
} private void DrawStart(Point StartPoint) 
{ 
   this.Capture = true; 
   Cursor.Clip = this.RectangleToScreen(this.Bounds); 
   MouseRect = new Rectangle(StartPoint.X,StartPoint.Y,0,0); 
} 在鼠标按下事件里写（一定是鼠标按下事件MouseDown   因为我的参数e是鼠标数据对象 
（不过你也可以传坐标）） 
MouseIsDown = true; 
DrawStart(e.Location); 在鼠标移动（MouseMove）事件里写     
if(MouseIsDown) 
    ResizeToRectangle(e.Location); 
在鼠标释放（MouseUp）事件里写       
this.Capture = false; 
Cursor.Clip = Rectangle.Empty; 
MouseIsDown = false; 
DrawRectangle(); 
MouseRect = Rectangle.Empty;

Answer 3

Cursor.Clip = this.RectangleToScreen(this.Bounds); 
的作用是限制鼠标不要超出绘图窗口，RectangleToScreen是转换到屏幕坐标系。这里的this与实际的绘图部分不一致时就有问题了，因此需要根据情况选择。

Answer 4

我试了一下，可是我拉出的虚线框并没有消失，应该是OnMouseUp事件出问题了，可是就是解决不了，郁闷:-(