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As you know, GetHashCode returns a semi-unique value that can be used to identify an object instance in a collection. As a good practice, it is recommended to override this method and implement your own.
My question is - do you override this method when working on custom objects? If so, what algorithm do you use to generate the unique ID?
I was thinking about generating a GUID and then getting integer data from that identificator.
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Why is it important to override GetHashCode ? It s important to implement both equals and gethashcode, due to collisions, in particular while using dictionaries. if two object returns same hashcode, they are inserted in the dictionary with chaining. While accessing the item equals method is used.
If you're implementing a reference type, you should consider overriding the Equals method if your type looks like a base type, such as Point, String, BigNumber, and so on. Override the GetHashCode method to allow a type to work correctly in a hash table.
You must override hashCode() in every class that overrides equals(). Failure to do so will result in a violation of the general contract for Object. hashCode(), which will prevent your class from functioning properly in conjunction with all hash-based collections, including HashMap, HashSet, and Hashtable.
Overriding only equals() method without overriding hashCode() causes the two equal instances to have unequal hash codes, which violates the hashCode contract (mentioned in Javadoc) that clearly says, if two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two ...
If you use resharper it can generate the GetHashCode(), Equals and operator method bodies for you.
Access this menu by pressing Alt+Insert.
http://www.jetbrains.com/resharper/webhelp/Code_Generation__Equality_Members.html
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When you override GetHashCode() you also need to override Equals(), operator== and operator!= . And be very careful to meet all the requirements for those methods.
The guidelines are here on MSDN. Most important quote:
It is not a good idea to override operator == in mutable types.
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