The is operator

The is operator is used to dynamically check if the run-time type of an object is compatible with a given type. The result of the operation E is T, where E is an expression and T is a type, is a boolean value indicating whether E can successfully be converted to type T by a reference conversion, a boxing conversion, or an unboxing conversion. The operation is evaluated as follows, after type arguments have been substituted for all type parameters:

· If E is an anonymous function, a compile-time error occurs

· If E is a method group or the null literal, of if the type of E is a reference type or a nullable type and the value of E is null, the result is false.

· Otherwise, let D represent the dynamic type of E as follows:

o If the type of E is a reference type, D is the run-time type of the instance reference by E.

o If the type of E is a nullable type, D is the underlying type of that nullable type.

o If the type of E is a non-nullable value type, D is the type of E.

· The result of the operation depends on D and T as follows:

o If T is a reference type, the result is true if D and T are the same type, if D is a reference type and an implicit reference conversion from D to T exists, or if D is a value type and a boxing conversion from D to T exists.

o If T is a nullable type, the result is true if D is the underlying type of T.

o If T is a non-nullable value type, the result is true if D and T are the same type.

o Otherwise, the result is false.

Note that user defined conversions, are not considered by the is operator.