How to use is,as,typeof,default operators?

Is and as operators are used to casting similar/compatable types only.and casting is done as per the holding value also.
but the scenerious are different.
IS

is operator is used to casting between 2 compatable types.

which create an expression, and returns a Boolean value.

isDemo:

string str = "propercode";

object obj = "20";

if (str is object)

{

Console.WriteLine("casting is possible");

}

if (str is StringBuilder)

{

Console.WriteLine(" casting not possible b/w string and sbuilder");

}

else

{

Console.WriteLine("both are incompatable types");

}

if (obj is string)

{

Console.WriteLine("casting is possible ");  //----"20"

}

else

{

Console.WriteLine("casting is not possible");//----20

}

In case of obj holding value as string  type then compatable is possible.if

In case of obj holding value as integer type then compatable is not possible.else

AS:

as operator is used to casting between 2 compatable types.

which doesn’t return any Boolean value.

            object obj = "20";

            string str2 = obj as string;

            Console.WriteLine(str2.GetType());

obj holds value as string so compatable is possible. incase of storing as integer error.

string str = "propercode";

            object objs = str as object;

            Console.WriteLine(objs.GetType());

But right hand side requires apporiate type variable.

Difference between typeof operator and GetType() Method?

Typeof(classname) operator

Type t = typeof(string);

            Console.WriteLine(t);

            Type t1 = typeof(Employee);

            Console.WriteLine(t1);

Typeof operator excepts classname to know the underlying type.

GetType() Method

            Type t1 = typeof(Employee);

            Console.WriteLine(t1);

               //or

            Employee eobj = new Employee();

            Console.WriteLine(eobj.GetType());

Requeries instance to know the underlying type.

default operator

             StringBuilder variable1 = default(StringBuilder);

            int variable2 = default(int);

            bool variable3 = default(bool);

            Program variable4 = default(Program);

            string s = default(string);

            // Write the values.

            Console.WriteLine(variable1); // Null

            Console.WriteLine(variable2); // 0

            Console.WriteLine(variable3); // False

            Console.WriteLine(variable4); // Null

            Console.WriteLine(s);