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What Does Mutator Mean?

A mutator, in the context of C#, is a method, with a public level of accessibility, used to modify and control the value of a private member variable of a class. The mutator is used to assign a new value to the private field of a type. It forms a tool to implement encapsulation by only controlling access to the internal field values that must be modified.


The benefits of using a mutator include:

  • Prevents the user from directly accessing the private data of an object instance and allows access only through public methods to prevent data corruption.
  • Provides flexibility in modifying the internal representation of the fields of an object that represents the internal state without breaking the interface used by the object’s clients.
  • Ability to include additional processing logic like validation of a values set, triggering of events, etc., during the modification of the field in the mutator.
  • Provides the synchronization that is necessary for multithreading scenarios.
  • Includes a provision to override the mutator declared in a base class with the code in the derived class.

Techopedia Explains Mutator

A mutator is usually provided with an accessor that returns the value of the member variable. For data members that are immutable, the mutator should not be provided.

For example, StudentData can be a class that stores a student’s details, such as name, address, grade, etc. There can be a public method, SetGrade in the class. StudentData is the mutator to update the StudentData object from the code that uses the object.

While a mutator is implemented in C++ by an explicit public method to modify a private field, C# introduces “properties” as a new feature that implements a mutator to modify field values as well as an accessor to fetch the field. Each property is represented in the common intermediate language code with a pair of methods prefixed with “get_”(accessor) and “set_”(mutator) under the hood. They are called internally by the common language runtime (CLR). This simplifies the code and sometimes allows for the performance of mathematical operations.

The mutator is not often used in objects, where the object’s behavior is considered rather than how it performs.


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Margaret Rouse

Margaret jest nagradzaną technical writerką, nauczycielką i wykładowczynią. Jest znana z tego, że potrafi w prostych słowach pzybliżyć złożone pojęcia techniczne słuchaczom ze świata biznesu. Od dwudziestu lat jej definicje pojęć z dziedziny IT są publikowane przez Que w encyklopedii terminów technologicznych, a także cytowane w artykułach ukazujących się w New York Times, w magazynie Time, USA Today, ZDNet, a także w magazynach PC i Discovery. Margaret dołączyła do zespołu Techopedii w roku 2011. Margaret lubi pomagać znaleźć wspólny język specjalistom ze świata biznesu i IT. W swojej pracy, jak sama mówi, buduje mosty między tymi dwiema domenami, w ten…