Paint different pictureboxes

Question

I have 3 pictureboxes. pb1, pb2 & pb3. Pb2 is my primary picturebox and double the size of the other. On these picture boxes I will draw a line based on some values. If value is less than 0 pb1 should be drawn upon and if the value is greater than 124 pb3 should be used.

I have then made this code if(value <0)

{
 pb1.paint += new PaintEventHandler(pb1_paint)
}

In the paint event I draw the line.

When running the project no line will be drawn on the picturebox, however, if I break the line will be drawn. What do I do wrong?

Answer 1

Because value>=0, I guess.
Your code will run only once. so when program reach that line, if value<0 then it will register event handler elsewhere it wont at all, even if you change the value to less than zero.
So I suggest following instead:

yourForm_Load()
{
  //ALWAYS REGISTER THE HANDLER
  pb1.paint += new PaintEventHandler(pb1_paint);
}

pb1_paint()
{
  //CHECK IF TO DRAW THAT LINE HERE INSTEAD
  if(value<0)
  {
     //TO DO: DRAW THAT LINE
  }
}

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Answer 2

Form1_Load()
{
pb1.Paint += new PaintEventHandler(pb1_Paint);
}


pb1_Paint
{

if(value<0)
{
pb2.paint += new PaintEventHandler(pb2_paint); 
If I just use g.drawline..... It will draw in the currenct picturebox.


}
else
{
 g.DrawLine(Pens.Black, 0, pb1.ClientSize.Height / 2, 100, pb1.ClientSize.Height / 2);
}

I will just write my code, as I have two paint event handlers like this.

Answer 3

So I suggest following

Form1_Load()
{
  pb1.Paint += new PaintEventHandler(pb1_Paint);
  pb2.Paint += new PaintEventHandler(pb2_Paint);
}

pb1_Paint
{
  if(value<0)
  {
     pb2.Invalidate();
  }
  else
  {
    g.DrawLine(Pens.Black, 0, pb1.ClientSize.Height / 2, 100, pb1.ClientSize.Height / 2);
  }
}

pb2_Paint
{
  if(value>=0)
  {
    g.DrawLine(Pens.Black, 0, pb2.ClientSize.Height / 2, 100, pb2.ClientSize.Height / 2);
  }
}

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Answer 4

Hello Scorgi,

I prefer Yasser’s solution. It is correct to tell PictureBox itself (pb2) draw the item instead of hand pb1.Paint to draw something on pb2. The recommended way is let each pictureBox draw element according to the value.

Sincerely,
Kira Qian
MSDN Subscriber Support in Forum
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Answer 5

Thank you very much!!! Worked perfectly!

Answer 6

You're welcome.
Thank you for your happiness :)
Have a good time!

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My Blog - MSDN Complement by providing Visual C# Walkthroughs and Sample Codes - Founded In February 24, 2010