Conversions - Illustrated C# 2005 - page 425

The is Operator
As shown previously, some conversion attempts are not successful, and raise an
InvalidCastException exception at run time. Instead of blindly attempting a conversion, you
can use the is operator to check whether a conversion would complete successfully.
The syntax of the is operator is the following, where Expr is the source expression:

Returns a bool
↓
Expr is TargetType

The operator returns true if Expr can be successfully converted to the target type through
any of the following:

￿ A reference conversion

￿ A boxing conversion

￿ An unboxing conversion

For example, in the following code, you use the is operator to check whether variable Bill
of type Employee can be converted to type Person , and then take the appropriate action.

class Employee : Person { }
class Person {
public string Name = "Anonymous";
public int Age = 25;
}

class Program {
static void Main()
{
Employee Bill = new Employee();
Person p;

// Check if variable Bill can be converted to type Person
if( Bill is Person ) {
p = Bill;
Console.WriteLine("Person Info: {0}, {1}", p.Name, p.Age);
}
}
}

The is operator can only be used for reference conversions and boxing and unboxing con-
versions. It cannot be used for user-defined conversions.