public Form1()
{
    InitializeComponent();
    this.Load += Form1_Load;

}
protected override bool IsRectangularShape(ref int radius)
{
    return false;
}

private void Form1_Load(object sender, EventArgs e)
{
    this.BorderColor = Color.Red;
    this.BorderWidth = 2;
    RoundRectShape roundRectShape = new RoundRectShape();
    roundRectShape.Radius = 30;
    roundRectShape.BottomRightRounded = false;
    roundRectShape.TopLeftRounded = false;
    this.Shape = roundRectShape;
}