增加窗体边框3D效果

/// <summary>
/// 增加窗体边框3D效果
/// </summary>
/// <param name="e"></param>
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
using (Pen bluePen = new Pen(Color.FromArgb(141, 178, 196)))
{
e.Graphics.DrawLine(bluePen, 1, 1, this.Width - 2, 1);
e.Graphics.DrawLine(bluePen, 1, 1, 1, this.Height - 2);
e.Graphics.DrawLine(bluePen, 1, this.Height - 2, this.Width - 2, this.Height - 2);
e.Graphics.DrawLine(bluePen, this.Width - 2, 1, this.Width - 2, this.Height - 2);
}
}