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The overridden base method must be virtual, abstract, or override. In addition to the modifiers that are used for method overriding, C# allows the hiding of an inherited property or method. This is done using the same signature of a property or method but adding the modifier new in front of it. [6] In the above example, hiding causes the following:
The functions must have different type signatures, i.e. differ in the number or the types of their formal parameters (as in C++) or additionally in their return type (as in Ada). [9] Function overloading is usually associated with statically-typed programming languages that enforce type checking in function calls. An overloaded function is a ...
Method overriding and overloading are two of the most significant ways that a method differs from a conventional procedure or function call. Overriding refers to a subclass redefining the implementation of a method of its superclass. For example, findArea may be a method defined on a shape class, [2] triangle, etc. would each define the ...
C# introduced support for dynamic multimethods in version 4 [8] (April 2010) using the 'dynamic' keyword. The following example demonstrates multimethods. Like many other statically-typed languages, C# also supports static method overloading. [9] Microsoft expects that developers will choose static typing over dynamic typing in most scenarios. [10]
The previous section notwithstanding, there are other ways in which ad hoc polymorphism can work out. Consider for example the Smalltalk language. In Smalltalk, the overloading is done at run time, as the methods ("function implementation") for each overloaded message ("overloaded function") are resolved when they are about to be executed.
This is supposed to avoid confusion between overriding and newly overloading a function (i.e. hiding the former implementation). To do the latter, you have to specify the new keyword. [84] You can use the keyword sealed to disallow further overrides for individual methods or whole classes. [85]
Thus, there is no name collision, and no virtual table lookup. By contrast, dynamic dispatch is based on the type of the calling object, meaning it uses virtual functions (overriding) instead of function overloading, and does result in a vtable lookup. Consider the following example, written in C++, of collisions in a game:
In object-oriented programming, a covariant return type of a method is one that can be replaced by a "narrower" (derived) type when the method is overridden in a subclass. A notable language in which this is a fairly common paradigm is C++. C# supports return type covariance as of version 9.0. [1]