Question

I am writing a program in Visual C# 2010 that has several icons on the form. When the mouse is placed over the icon (which is just an image) I want the icon to b highlighted via a border around the icon. In visual basic i can make a transparent rectangle with a colored border and position it over the icon. In C#, i can do the same however until i call invalidate multiple borders appear. The problem with calling invalidate is that my program is doing something in the background every second so the border keeps flashing (re-drawing).

Anyone got any ideas how i can implement this?

Answer 1

You didn’t say how you draw the border but from your description you are creating a graphics context for this. Don’t do this, it’s wrong. Instead, draw inside the Paint element of either the control or the its parent container.

The Paint event handler could look as follows:

private void yourControl_Paint(object sender, PaintEventArgs e)
{
    if (! HasFocus(yourControl))
        return;
    Graphics g = e.Graphics;
    using (Pen p = new Pen(Color.FromArgb(128, 0, 0, 128)))
        g.DrawRectangle(p, 0, 0, yourControl.Width -1, yourControl.Height - 1);
}

This uses a hypothetical HasFocus method to determine whether this control should have a focus rectangle.

By the way, this is identical in VB and C#.