is Operator and as Operator :-

The "is" operator is used to check whether the run-time type of an object is compatible with a given type or not. In other words, we use the "is" operator to verify that the type of an object is what we expect it to be. Let's look at its syntax:

expression is type

Example of the "is" operator:

usingSystem;
classClass1
{ }
classClass2
{ }
public classIsTest
{
public static void Test(object o)
{
Class1 a;
Class2 b;
if(o is Class1)
{
Console.WriteLine("o is Class1");
a = (Class1)o;
}
elseif(o is Class2)
{
Console.WriteLine("o is Class2");
b = (Class2)o;
}
else
{
Console.WriteLine("o is neither Class1 nor Class2.");
}
}
publicstaticvoidMain()
{
Class1 c1 =new Class1();
Class2 c2 =new Class2();
Test(c1);
Test(c2);
Test("Passing String Value instead of class");
Console.ReadKey();
}
}

In the above example, I'll be checking whether object o is a class or not. If the argument passed is not a class then the application will jump to the message 'o is neither class1 nor class2'.

as Operator

The "as" operator is used to perform conversions between compatible types. Actually, the "as" operator fulfills a similar role like "is" but in a slightly truncated manner. Let's look at its syntax:

expression as type

Example of the "is" operator:

usingSystem;
classClass1
{
}
classClass2
{
}
publicclassIsTest
{
public static void Main()
{
object[] myObjects =new object[6];
myObjects[0] =new Class1();
myObjects[1] =new Class2();
myObjects[2] ="string";
myObjects[3] = 32;
myObjects[4] =null;
for(inti = 0; i < myObjects.Length; ++i)
{
strings = myObjects[i] as string;
Console.Write("{0}:", i);
if(s !=null)
Console.WriteLine("'"+ s +"'");
else
Console.WriteLine("not a string");
}
Console.ReadKey();
}
}

In the above example, each and every value is being cast to a string using the "as" operator and assigned to a string variable which is shown on the console.

So, that's all about the "is" and "as" operators.