Performance (C# Programming Guide)
This section covers two issues that can adversely effect performance, and links to resources on performance issues.
Boxing and Unboxing
Boxing and unboxing are computationally expensive processes. When a value type is boxed, an entirely new object must be created. This can take up to 20 times longer than an assignment. When unboxing, the casting process can take four times as long as an assignment. For more information, see Boxing and Unboxing.
Empty destructors should not be used. When a class contains a destructor, an entry is created in the Finalize queue. When the destructor is called, the garbage collector is invoked to process the queue. If the destructor is empty, this simply results in a loss of performance. For more information, see Destructors.