Draw a Border around any C# Winform Control

public class MyGroupBox : GroupBox
{
    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        ControlPaint.DrawBorder(e.Graphics, ClientRectangle,
                                     Color.Black, BORDER_SIZE, ButtonBorderStyle.Inset,
                                     Color.Black, BORDER_SIZE, ButtonBorderStyle.Inset,
                                     Color.Black, BORDER_SIZE, ButtonBorderStyle.Inset,
                                     Color.Black, BORDER_SIZE, ButtonBorderStyle.Inset);
    }
}

转自：Codeproject