c# – how to make this code as different manner? [closed]

How about?

public abstract class Shape
{
    public abstract int CalcArea();
}

public class Rectangle : Shape
{
    public int Height { get; set; }
    public int Width { get; set; }

    public override int CalcArea()
    {
        return Height * Width;
    }
}

public class Circle : Shape
{
    public float Radius { get; set; }

    public override int CalcArea()
    {
        return Math.PI * (Radius * Radius);
    }
}