Question

I’m trying to get from Line #1 to Line #2 in the below code:

using System;  
using System.Windows.Forms;  

namespace MyNameSpace  
{  
    internal class MyTextBox : System.Windows.Forms.TextBox  
    {  
        protected override void OnEnabledChanged(EventArgs e)  
        {  
            base.OnEnabledChanged(e);  
            Invalidate(); // Line #1 - can get here  
            Refresh();  
        }

       protected override void OnPaint(PaintEventArgs e)  
       {
            base.OnPaint(e);   
            System.Diagnostics.Debugger.Break(); // Line #2 - can't get here  
       }  
    }  
}  

However, it seems that neiter Invalidate() nor Refresh() causes OnPaint(PaintEventArgs e) to be invoked. Two questions:

1. Why doesn’t it work?
2. If it can’t be fixed: I only want to invoke OnPaint(PaintEventArgs e) in order to access the e.Graphics object – is there any other way to do this?

Answer 1

To override the drawing of the control, you must set the style to be UserPaint like this:

this.SetStyle(ControlStyles.UserPaint, true);

See this for more information:

http://msdn.microsoft.com/en-us/library/system.windows.forms.control.setstyle.aspx

UserPaint If true, the control paints
itself rather than the operating
system doing so. If false, the Paint
event is not raised. This style only
applies to classes derived from
Control.