Does c# have the same issues like Java with equals and gethashcode?
issues like: http://onjava.com/pub/a/onjava/2006/09/13/dont-let-hibernate-steal-your-identity.html
+3
A:
Not sure which issues you're talking about since you're a little vague...
But if you mean that you have should (if you don't want a compiler warning, or possibly unexpected behavior in your code) to override GetHashCode when you override Equals, then yes.
Justin Niessner
2010-04-16 18:18:18
+11
A:
If you mean that equality is hard to define when it comes to inheritance, yes.
However, .NET has the IEqualityComparer<T> interface which is frequently used for equality and hashing - for containers such as Dictionary<TKey, TValue>. Almost everything in the framework which needs equality/hashing allows the behaviour to be specified by an IEqualityComparer<T>, which means you can express whichever notion of equality you want, if the form given by the type itself is inappropriate for your needs.
Jon Skeet
2010-04-16 18:20:24
Issues like: http://onjava.com/pub/a/onjava/2006/09/13/dont-let-hibernate-steal-your-identity.html
Blankman
2010-04-16 18:49:31
@Blankman: Right - so basically you want two different concepts of equality; one by ID and one by various fields. That's exactly what `IEqualityComparer<T>` is for.
Jon Skeet
2010-04-16 19:54:07
so Collections use IEqualityComparer<T>? if yes, it seems a little more robust than Java.
Blankman
2010-04-16 21:14:58
@Blankman: Yes, things like `HashSet<T>` allow you to specify a custom comparator when you create them.
Jon Skeet
2010-04-16 21:31:58