I am new to C# and trying to make a volume cal that allows you to choose the shape you want to find the volume of I am trying to do that with read line. I am getting Cannot convert type 'String' to 'AreaCal.VolumeSphere' at the read line in static void main

```
using System;

namespace AreaCal
{

    class VolumeSphere
    {
        double pi = 3.14159265359;
        double ft = 1.333333333333333333333333333333333333;
        double r;
        public void Details()
        {
            Console.WriteLine("Volume of a Circle");
            Console.WriteLine ("Type Radius");
            r = Convert.ToInt32 (Console.ReadLine ());

        }
        public double GetVolume()
        {
            return ft * pi * r * r * r;
        }
        public void Display()
        {
            Console.WriteLine ("Volume: {0}", GetVolume());
        }

    }
    class MainClass
    {
        public static void Main (string[] args)
        {
            VolumeSphere Sphere = new VolumeSphere ();
            Sphere = (Console.ReadLine ());
            if (Sphere != null)
                Console.WriteLine ("awwww");

        }
    }
}

```