Collection with multiple keys

Question

Hi,

I've seen collections where elements can be accessed using different 'keys' or accessors in an overloaded array sort of way. Let me show you what I mean:

MyCollection[3] would get the 4th object in the collection
MyCollection["title"] would get the object with a title of 'title'
MyCollection[SomeObj] would get the object with the matching SomeObj

I'm not sure how this is done; through some type of extended collection or using some type of interface. Does anyone have any simple examples of doing this? Or any suggestions on what I might be trying to do?

Many thanks,

Rob

Bechir Bejaoui · Answer

I give a code supose that you want to create your customized container object witch called MyCollection that contains ints If you are using the classic way (without generics) using System.Collection; public class MyCollection { private ArrayList list; public MyCollection() { list = new ArrayList(); } public int this[int Index] { get { return (int)list[Index]; } set { list[Index] = value; } } public int this[string ID] { get { return (int)list[ID]; } set { list[ID] = value; } } ............ } If you are using the new way (with generics) introduced within the 2.0 version here you is the code class MyCollection { private T[] arr; public MyCollection(int Dimension) { arr = new T[Dimension]; } public T this[int Index] { get { return arr[Index]; } set { arr[Index] = value; } } public T this[string ID] { get { return arr[ID]; } set { arr[ID] = value; } } .... }

Jan Montano · Answer

This will give you an idea: Creating Your Own Collections

Dipal Choksi · Answer

Check out Indexers in .Net. You will need to overload indexers to setup the multiple access mechanisms.

Collection with multiple keys

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Answers (3)