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GDI Drawing Lines triggered off a button click.

Posted on 2004-04-01
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Last Modified: 2010-05-18
I have no problem with the following code:

/***************************
      protected override void OnPaint(PaintEventArgs pe)
      {
            Graphics g = pe.Graphics ;
            Pen L1Pen = new Pen(Color.Red);
            Point L1x = new Point(100, 800);
            Point L1y = new Point(275, 800);
            
            Pen L2Pen = new Pen(Color.Blue);
            Point L2x = new Point(275, 800);
            Point L2y = new Point(625, 800);
            
            Pen L3Pen = new Pen(Color.Orange);
            Point L3x = new Point(625, 800);
            Point L3y = new Point(775, 800);
            
            Pen L4Pen = new Pen(Color.Black);
            Point L4x = new Point(775, 800);
            Point L4y = new Point(950, 800);
            
            
            
            g.DrawLine(L1Pen, L1x, L1y);
            g.DrawLine(L2Pen, L2x, L2y);
            g.DrawLine(L3Pen, L3x, L3y);
            g.DrawLine(L4Pen, L4x, L4y);
      }

***************/

However when I attempt to build the following code to trigger it in a off a button click I receive the following build error: The type or namespace name 'pe' could not be found (are you missing a using directive or an assembly reference?)
.

For example:
/*******************************
private void button1_Click(object sender, System.EventArgs e)
      {
            Graphics g = pe.Graphics ;
            Pen L1Pen = new Pen(Color.Red);
            Point L1x = new Point(100, 800);
            Point L1y = new Point(275, 800);
            
            Pen L2Pen = new Pen(Color.Blue);
            Point L2x = new Point(275, 800);
            Point L2y = new Point(625, 800);
            
            Pen L3Pen = new Pen(Color.Orange);
            Point L3x = new Point(625, 800);
            Point L3y = new Point(775, 800);
            
            Pen L4Pen = new Pen(Color.Black);
            Point L4x = new Point(775, 800);
            Point L4y = new Point(950, 800);
            
            
            
            g.DrawLine(L1Pen, L1x, L1y);
            g.DrawLine(L2Pen, L2x, L2y);
            g.DrawLine(L3Pen, L3x, L3y);
            g.DrawLine(L4Pen, L4x, L4y);
}

**************/
0
Comment
Question by:int200
  • 2
  • 2
4 Comments
 
LVL 5

Accepted Solution

by:
millsoft earned 500 total points
ID: 10736225
Hi int200,

In the first function 'pe' is an argument to the Paint function.  You need to get the Graphics object to the window upon which you want to draw in the Click Event.

Is it the Button's parent window?  
For example:

            private void PaintMe( Graphics g )
            {
                  Pen L1Pen = new Pen(Color.Red);
                  Point L1x = new Point(10, 80);
                  Point L1y = new Point(27, 80);
         
                  Pen L2Pen = new Pen(Color.Blue);
                  Point L2x = new Point(27, 80);
                  Point L2y = new Point(62, 80);
         
                  Pen L3Pen = new Pen(Color.Orange);
                  Point L3x = new Point(62, 80);
                  Point L3y = new Point(77, 80);
         
                  Pen L4Pen = new Pen(Color.Black);
                  Point L4x = new Point(77, 80);
                  Point L4y = new Point(95, 80);
         
         
         
                  g.DrawLine(L1Pen, L1x, L1y);
                  g.DrawLine(L2Pen, L2x, L2y);
                  g.DrawLine(L3Pen, L3x, L3y);
                  g.DrawLine(L4Pen, L4x, L4y);
            }

            private void button1_Click(object sender, System.EventArgs e)
            {
                  System.Windows.Forms.Button b = (System.Windows.Forms.Button) sender;
                  PaintMe( b.Parent.CreateGraphics() );
            }
Cheers!
Brad
0
 

Author Comment

by:int200
ID: 10738275
Thanks for the response, but I just put in your code and can not see any graphics drawn on the window.  I created a simple C# Windows App, created a button to the form and added your code.
Here is the entire code:

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace GDITest2
{
      /// <summary>
      /// Summary description for Form1.
      /// </summary>
      public class Form1 : System.Windows.Forms.Form
      {
            private System.Windows.Forms.Button button1;
            /// <summary>
            /// Required designer variable.
            /// </summary>
            private System.ComponentModel.Container components = null;

            public Form1()
            {
                  //
                  // Required for Windows Form Designer support
                  //
                  InitializeComponent();

                  //
                  // TODO: Add any constructor code after InitializeComponent call
                  //
            }

            /// <summary>
            /// Clean up any resources being used.
            /// </summary>
            protected override void Dispose( bool disposing )
            {
                  if( disposing )
                  {
                        if (components != null)
                        {
                              components.Dispose();
                        }
                  }
                  base.Dispose( disposing );
            }

            #region Windows Form Designer generated code
            /// <summary>
            /// Required method for Designer support - do not modify
            /// the contents of this method with the code editor.
            /// </summary>
            private void InitializeComponent()
            {
                  this.button1 = new System.Windows.Forms.Button();
                  this.SuspendLayout();
                  //
                  // button1
                  //
                  this.button1.Location = new System.Drawing.Point(72, 64);
                  this.button1.Name = "button1";
                  this.button1.Size = new System.Drawing.Size(96, 32);
                  this.button1.TabIndex = 0;
                  this.button1.Text = "button1";
                  //
                  // Form1
                  //
                  this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
                  this.ClientSize = new System.Drawing.Size(292, 266);
                  this.Controls.Add(this.button1);
                  this.Name = "Form1";
                  this.Text = "Form1";
                  this.ResumeLayout(false);

            }
            #endregion

            
            private void PaintMe( Graphics g )
            {
                  Pen L1Pen = new Pen(Color.Red);
                  Point L1x = new Point(100, 1000);
                  Point L1y = new Point(100, 825);
         
                  Pen L2Pen = new Pen(Color.Blue);
                  Point L2x = new Point(100, 825);
                  Point L2y = new Point(100, 475);
         
                  Pen L3Pen = new Pen(Color.Orange);
                  Point L3x = new Point(100, 475);
                  Point L3y = new Point(100, 325);
         
                  Pen L4Pen = new Pen(Color.Black);
                  Point L4x = new Point(100, 325);
                  Point L4y = new Point(275, 325);
         
         
         
                  g.DrawLine(L1Pen, L1x, L1y);
                  g.DrawLine(L2Pen, L2x, L2y);
                  g.DrawLine(L3Pen, L3x, L3y);
                  g.DrawLine(L4Pen, L4x, L4y);
            }

            private void button1_Click(object sender, System.EventArgs e)
            {
                  System.Windows.Forms.Button b = (System.Windows.Forms.Button) sender;
                  PaintMe( b.Parent.CreateGraphics() );
            }

            /// <summary>
            /// The main entry point for the application.
            /// </summary>
            [STAThread]
            static void Main()
            {
                  Application.Run(new Form1());
            }
      }
}

Thanks
0
 
LVL 5

Expert Comment

by:millsoft
ID: 10738334
There are two possibilites.

First, it doesn't appear the button has a event handler wired up.

You need something like
this.button1.click += new ....

I'm not at my C# machine so I don't have the exact syntax handy.

Second, the Y coordinate you are using (825) is probably off the bottom of the window.  That is why I used 80 instead for testing purposes.

0
 

Author Comment

by:int200
ID: 10738362
Hi Brad,

You were correct, I didn't double click on the button from the form which auto-generates the handler.  I just added the button and put the code in.

It works fine now.  Thanks!  By the way, I'm running 1600x1200 so that's why I'm using such large values.

Now, I need to look into how to pass variables a the points so I can use one function I can pass the x and y coorinates to.

Thanks and Best Regards!
0

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