drawing - how to stop flickering C# winforms

Question

I have a program that is essentially like a paint application. However, my program has some flickering issues. I have the following line in my code (which should get rid of flickering - but doesn't):

this.SetStyle(ControlStyles.AllPaintingInWmPaint 
| ControlStyles.UserPaint | ControlStyles.DoubleBuffer, true);

my code(minus the super and sub classes for the shapes is as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Paint
{
    public partial class Paint : Form
    {
        private Point startPoint;
        private Point endPoint;
        private Rectangle rect = new Rectangle();
        private Int32 brushThickness = 0;
        private Boolean drawSPaint = false;
        private List<Shapes> listOfShapes = new List<Shapes>();
        private Color currentColor;
        private Color currentBoarderColor;
        private Boolean IsShapeRectangle = false;
        private Boolean IsShapeCircle = false;
        private Boolean IsShapeLine = false;

        public SPaint()
        {

            InitializeComponent();
            this.SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint | ControlStyles.DoubleBuffer, true);

            currentColor = Color.Red;
            currentBoarderColor = Color.DodgerBlue;
            IsShapeRectangle = true; 
        }

        private void panelArea_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = panelArea.CreateGraphics();

            if (drawSPaint == true)
            {

                Pen p = new Pen(Color.Blue);
                p.DashStyle = System.Drawing.Drawing2D.DashStyle.Dash;

                if (IsShapeRectangle == true)
                {
                    g.DrawRectangle(p, rect);
                }
                else if (IsShapeCircle == true)
                {
                    g.DrawEllipse(p, rect);
                }
                else if (IsShapeLine == true)
                {
                    g.DrawLine(p, startPoint, endPoint);
                }
            }
            foreach (Shapes shape in listOfShapes)
            {

                shape.Draw(g);

            }
        }

        private void panelArea_MouseDown(object sender, MouseEventArgs e)
        {

            startPoint.X = e.X;
            startPoint.Y = e.Y;

            drawSPaint = true;
        }

        private void panelArea_MouseMove(object sender, MouseEventArgs e)
        {


            if (e.Button == System.Windows.Forms.MouseButtons.Left)
            {

                if (e.X > startPoint.X)
                {
                    rect.X = startPoint.X;
                    rect.Width = e.X - startPoint.X;
                }
                else
                {
                    rect.X = e.X;
                    rect.Width = startPoint.X - e.X;
                }
                if (e.Y > startPoint.Y)
                {
                    rect.Y = startPoint.Y;
                    rect.Height = e.Y - startPoint.Y;
                }
                else
                {
                    rect.Y = e.Y;
                    rect.Height = startPoint.Y - e.Y;
                }


                panelArea.Invalidate();

            }

        }

        private void panelArea_MouseUp(object sender, MouseEventArgs e)
        {

            endPoint.X = e.X;
            endPoint.Y = e.Y;

            drawSPaint = false;

            if (rect.Width > 0 && rect.Height > 0)
            {
                if (IsShapeRectangle == true)
                {
                    listOfShapes.Add(new TheRectangles(rect, currentColor, currentBoarderColor, brushThickness));
                }
                else if (IsShapeCircle == true)
                {
                    listOfShapes.Add(new TheCircles(rect, currentColor, currentBoarderColor, brushThickness));
                }
                else if (IsShapeLine == true)
                {
                    listOfShapes.Add(new TheLines(startPoint, endPoint, currentColor, currentBoarderColor, brushThickness));
                }

                panelArea.Invalidate();
            }
        }


        private void rectangleToolStripMenuItem_Click(object sender, EventArgs e)
        {
            IsShapeRectangle = true;
            IsShapeCircle = false;
            IsShapeLine = false; 
        }

        private void ellipseToolStripMenuItem_Click(object sender, EventArgs e)
        {
            IsShapeRectangle = false;
            IsShapeCircle = true;
            IsShapeLine = false; 
        }

        private void lineToolStripMenuItem_Click(object sender, EventArgs e)
        {
            IsShapeCircle = false;
            IsShapeRectangle = false;
            IsShapeLine = true; 
        }

        private void ThicknessLevel0_Click(object sender, EventArgs e)
        {
            brushThickness = 0; 
        }

        private void ThicknessLevel2_Click(object sender, EventArgs e)
        {
            brushThickness = 2; 
        }

        private void ThicknessLevel4_Click(object sender, EventArgs e)
        {
            brushThickness = 4; 
        }

        private void ThicknessLevel6_Click(object sender, EventArgs e)
        {
            brushThickness = 6; 
        }

        private void ThicknessLevel8_Click(object sender, EventArgs e)
        {
            brushThickness = 8; 
        }

        private void ThicknessLevel10_Click(object sender, EventArgs e)
        {
            brushThickness = 10; 
        }

        private void ThicknessLevel12_Click(object sender, EventArgs e)
        {
            brushThickness = 12; 
        }

        private void ThicknessLevel14_Click(object sender, EventArgs e)
        {
            brushThickness = 14; 
        }

        private void FillColour_Click(object sender, EventArgs e)
        {

            ColorDialog fillColourDialog = new ColorDialog();
            fillColourDialog.ShowDialog();
            currentColor = fillColourDialog.Color;
            panelArea.Invalidate(); 
        }

        private void button1_Click(object sender, EventArgs e)
        {

            ColorDialog fillColourDialog = new ColorDialog();
            fillColourDialog.ShowDialog();
            currentBoarderColor = fillColourDialog.Color;
            panelArea.Invalidate(); 
        }


    }
}

How do i stop the flickering?

*UPDATE:*This code actually works great when i'm drawing directly on the form. However, when i try to draw on the panel, flickering becomes an issue

Answer 1

For a "cleaner solution" and in order to keep using the base Panel, you could simply use Reflection to implement the double buffering, by adding this code to the form that holds the panels in which you want to draw in

    typeof(Panel).InvokeMember("DoubleBuffered", 
    BindingFlags.SetProperty | BindingFlags.Instance | BindingFlags.NonPublic, 
    null, DrawingPanel, new object[] { true });

Where "DrawingPanel" is the name of the panel that you want to do the double buffering.

I know quite a lot of time has passed since the question was asked, but this might help somebody in the future.