What do you mean by Override?

Question

1.What do you mean by Override?What's the use of it? Any simple example/Article? 2. What's the meaning of keywords in the following: protected override void OnMouseMove(MouseEventArgs e)

alobiuc · Answer

Oh I forgot to mention: -aside methods also properties and indexers can be overriden; -the base method can (must) be marked as virtual or as abstract; -the signature of the overriden property must match exactly the base property. For more info take a look here: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/csref/html/vclrfoverridepg.asp

alobiuc · Answer

1. To override a method means to implement a different behaviour of it than the original one. For example if you have a base class which implements a certain method and you want it to behave differently in a derived class you override it in the derived class. In order for a method to be overriden it must be marked as virtual in the base class: class BaseClass { public BaseClass(){} public virtual void method1(int x) {Console.Writeline(X is: {0}x);} } class DerivedClass: BaseClass { public DerivedClass(){} public override void method1(int x) {Console.Writeline(X+1 is {0}(x+1));} } class MainClass {public MainClass(){} BaseClass b=new BaseClass(); DerivedClass d=new DerivedClass(); b.method1(10);//output: X is 10 d.method1(10);//output: X+1 is 11; } If you hadn't overriden the method1 in DerivedClass and you would call: d.method1(10) the output would be: X is 10. 2. protected -- the access level for the method override -- as described at (1) void -- return type MouseEventArgs e -- this is not a keyword but a parameter of type MouseEventArgs a class that holds informations about a MouseEvent. Also this is a class derived from the Event class.