c# - Double buffering doesn't work on a panel?

Question

I'm working on a small painting program similar to ms paint. At the moment, I'm trying to implement 'select function'. I'm facing flickering problem so I've did some researches and I found out, that I should create my own Panel class.

public class MyDisplay : Panel
    {   
        public MyDisplay()
        {
            this.DoubleBuffered = true;            

            this.SetStyle(ControlStyles.UserPaint |
              ControlStyles.AllPaintingInWmPaint |
              ControlStyles.ResizeRedraw |
              ControlStyles.ContainerControl |
              ControlStyles.OptimizedDoubleBuffer |
              ControlStyles.SupportsTransparentBackColor
              , true);

            this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
            this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
            this.UpdateStyles();
        }
    }

In main form there are fields:

MyDisplay panel1 = new MyDisplay();
Graphics graphics1 = panel1.CreateGraphics();

I use 3 events on a panel:

1. MouseDown - I get here Point p1
2. MouseMove - thats, where I get flickering problem, I'm calling graphics1.drawRectangle(...) and graphics1.Clear() everytime clicked mouse moves
3. MouseUp - I just draw rectangle for the last time.

What's wrong with that? Why do I still face flickering problem even though whole panel is white and theres only 1 rectangle in there? Thank you.

edit:

I've overwrote OnPaint method but I still don't know what to do next.

   protected override void OnPaint(PaintEventArgs e)
    {
        // Call the OnPaint method of the base class.
        base.OnPaint(e);
        // Call methods of the System.Drawing.Graphics object.
        e.Graphics.DrawString(Text, Font, new SolidBrush(ForeColor), ClientRectangle);
    } 

edit2: Should I paint on bitmap/image and override OnPaint method to copy image from there and paste it to panel?

Answer 1

删除定义graphics1字段的行。

使用通过 PaintEventArgs 对象传入的 Graphics 对象，在 OnPaint 的覆盖中执行所有绘制。使用方法 Invalidate()、Refresh() 和 Update() 来控制从其他代码重新绘制的时间。

如果您在此设计中遇到任何特定困难，请回调。