What is the difference between “is” and “as” operators?

 

In C#, the "is" and "as" operators are used for type checking and type casting, but they have different behaviors and purposes:

"is" Operator: The "is" operator is used for type checking. It evaluates whether an object is of a specific type or a type that derives from a specific type. The result of the "is" operator is a Boolean value (true or false) indicating the outcome of the type check.

Syntax:

object obj = // some object or expression;
if (obj is SomeType)
{
    // Code executed if obj is of SomeType or its derived types
}

The "is" operator checks if the object referenced by obj is an instance of SomeType or any type derived from SomeType. If the check succeeds, the code inside the if statement is executed.

"as" Operator: The "as" operator is used for safe type casting. It attempts to cast an object to a specified type. If the cast is successful, it returns the object as the specified type. If the cast fails, it returns null instead of throwing an exception.

Syntax:

object obj = // some object or expression;
SomeType result = obj as SomeType;
if (result != null)
{
    // Code executed if obj can be successfully cast to SomeType
}

The "as" operator attempts to cast the object referenced by obj to SomeType. If the cast succeeds, the result will be assigned to the variable result, which can be used further in the code. If the cast fails, result will be assigned null. This allows you to check the success of the cast using a null check.

To summarize:

• "is" operator: Checks if an object is of a specific type or derived from a specific type.
• "as" operator: Attempts to cast an object to a specified type, returning null if the cast fails.

It's important to note that the "as" operator only works with reference types and nullable value types, while the "is" operator can be used with any type, including value types.