Create custom ComboBox control, and override it's WndProc
method. You can easily draw a border with ControlPaint.DrawBorder method:
public class ComboBoxWithBorder : ComboBox
{
private Color _borderColor = Color.Black;
private ButtonBorderStyle _borderStyle = ButtonBorderStyle.Solid;
private static int WM_PAINT = 0x000F;
protected override void WndProc(ref Message m)
{
base.WndProc(ref m);
if (m.Msg == WM_PAINT)
{
Graphics g = Graphics.FromHwnd(Handle);
Rectangle bounds = new Rectangle(0, 0, Width, Height);
ControlPaint.DrawBorder(g, bounds, _borderColor, _borderStyle);
}
}
[Category("Appearance")]
public Color BorderColor
{
get { return _borderColor; }
set
{
_borderColor = value;
Invalidate(); // causes control to be redrawn
}
}
[Category("Appearance")]
public ButtonBorderStyle BorderStyle
{
get { return _borderStyle; }
set
{
_borderStyle = value;
Invalidate();
}
}
}
BTW There is also overloaded DrawBorder method, which allows to set width of border. Use it if you need.
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