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.NET Forum / Languages / C# / March 2008Define operator == and !=
Hello! If I define operator == and != is then nessesary to override method Equals and GetHashCode that is inherited from System.Object ? If yes will Equals have the same functionalitty as operator == ? So can I then just restrict the functionality to one method and just call this method from the other ? Does this sound correct ? //Tony > If I define operator == and != is then nessesary to override method Equals > and GetHashCode that is inherited from > System.Object ? It's at least a very good idea to do so. > If yes will Equals have the same functionalitty as operator == ? Again, it's a very good idea to make Equals and == do the same thing. > So can I then just restrict the functionality to one method and just call > this method from the other ? > > Does this sound correct ? Yes.  SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet World class .NET training in the UK: http://iterativetraining.co.uk > Hello! > [quoted text clipped - 10 lines] > > //Tony They are not strictly identical, as operator== might be called with two null references, whereas this cannot arise when you are overriding object's virtual Equals method. If using VS2005, overriding GetHashCode is very simple - when you type "public override" the intellisense suggests things you can override - if you click GetHashCode it writes the whole function for you, calling "base.GetHashCode()". You only need to rewrite the code in it if your redefinition of equality causes two objects that are "equal" give different hash codes. <snip> > If using VS2005, overriding GetHashCode is very simple - when you type > "public override" the intellisense suggests things you can override - if you > click GetHashCode it writes the whole function for you, calling > "base.GetHashCode()". You only need to rewrite the code in it if your > redefinition of equality causes two objects that are "equal" give different > hash codes. On the other hand, that's true of all of ==, !=, Equals and GetHashCode. If the default implementation isn't appropriate for one of them, chances are it won't be appropriate for any of them - at least for reference types. SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet World class .NET training in the UK: http://iterativetraining.co.uk
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