Casting an expression to the type that it already has serves no purpose and clutters the code. It indicates confusion about the type of the expression, or that the code has been partially refactored.

This query applies to both the () operator and the as operator.

In all cases, the redundant cast should simply be removed.

The following example shows a getter where the return value is explicitly cast to an int. However this is unnecessary because the type of the expression properties["Size"] is already int.

The problem is resolved by deleting the useless (int).

MSDN, C# Programming Guide: Casting and Type Conversions.