Panel圆角处理

private void SetWindowR()
{
    System.Drawing.Drawing2D.GraphicsPath gPath = new System.Drawing.Drawing2D.GraphicsPath();
    Rectangle rect = new Rectangle(0,0, this.panel1.Width, this.panel1.Height);
    gPath = GetRoundedRP(rect, 10); 
    this.panel1.Region = new Region(gPath);
}

private System.Drawing.Drawing2D.GraphicsPath GetRoundedRP(Rectangle rect, int a)
{
    int diameter = a;
    Rectangle arcRect = new Rectangle(rect.Location, new Size(diameter, diameter));
    System.Drawing.Drawing2D.GraphicsPath gp = new System.Drawing.Drawing2D.GraphicsPath();
    gp.AddArc(arcRect, 180, 90);
    arcRect.X = rect.Right - diameter;
    gp.AddArc(arcRect, 270, 90);
    arcRect.Y = rect.Bottom - diameter;
    gp.AddArc(arcRect, 0, 90);
    arcRect.X = rect.Left;
    gp.AddArc(arcRect, 90, 90);
    gp.CloseFigure();
    return gp;
}

如果要设置圆角的控件不需要动态设置尺寸，可以直接复写OnResize(), 如下：

protected override void OnResize(EventArgs e)
{
    base.OnResize(e);
    this.panel1.Region = null;
    SetWindowR();
}

如果控件是动态设置尺寸的，就在设置尺寸的方法里调用即可。