C# Override MethodThis C# article shows how the override keyword works on virtual base methods.
Override affects virtual method usage. Virtual methods are meant to be re-implemented in derived classes. The override keyword specifies that a method replaces its virtual base method.
illustrates the difference between an override method in a derived class, and a method that is not an override method. It does nothing useful but helps us learn about override methods.
Here: In the example, the class A is the base class. It has the virtual method Y.Virtual
And: In class B, we override Y. In class C, we implement Y but do not specify that it overrides the base method.Class
C# program that uses override modifier
public virtual void Y()
// Used when C is referenced through A.
class B : A
public override void Y()
// Used when B is referenced through A.
class C : A
public void Y() // Can be "new public void Y()"
// Not used when C is referenced through A.
static void Main()
// Reference B through A.
A ab = new B();
// Reference C through A.
A ac = new C();
The A type is used to reference the B and C types. When the A type references a B instance, the Y override from B is used. But when the A type references a C instance, the Y method from the base class A is used.
Note: The override modifier was not used. The C.Y method is local to the C type.
Warning: In the above program, the C type generates a warning because C.Y hides A.Y. Your program is confusing and could be fixed.
Tip: If you want C.Y to really "hide" A.Y, you can use the new modifier, as in "new public void Y()" in the declaration.New
The C# specification helps us understand override methods. With override, we specialize an "existing inherited virtual method." We provide a new implementation for it. This is at first confusing.
Tip: I recommend writing a test program to see how this works. This may help you understand.
Quote: Whereas a virtual method introduces a new method, an override method specializes an existing inherited virtual method by providing a new implementation of that method (The C# Programming Language).
The override modifier is needed for implementing polymorphic behaviors in derived classes. You can re-implement a virtual base method. This causes the base implementation to be ignored in favor of the "override" method.
And: This polymorphic behavior is core to object-oriented design in many programs.
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