var obj = new Student("Muhammad");
var obj2 = new SpecialStudent("Muhammad", "Siddiqi");

Console.WriteLine(
            "Is IStudent: {0}, Is Student: {1}, Is SpecialStudent: {2}",
            obj is IStudent,
            obj is Student,
            obj is SpecialStudent); //True, True, False

Console.WriteLine(
            "Is IStudent: {0}, Is Student: {1}, Is SpecialStudent: {2}",
            obj2 is IStudent,
            obj2 is Student,
            obj2 is SpecialStudent); //True, True, True

Console.WriteLine(
            "Is Student Object implements ICalculator<int> interface: {0}",
            obj is ICalculator<int>); //False