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Multiple Indexers in C#

, 25 Jan 2012
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An elegant programmatic solution for having multiple indexers in C#
In C#, you can't have multiple indexers like you can do in VB, so the following code is not supported:
class C
    public Foo Foos[int i]
    public Bar Bars[int i]
On the other hand, exposing internal IEnumerable is not always a desired solution (because you want to limit access to your internal collections - that's why indexers are for in the first place.)


I came up with this simple class that you can add to your code:
public class IndexProperty<T,I>
       private Func<I,T> getter;
       private Action<I, T> setter;
       public IndexProperty(Func<I, T> g, Action<I, T> s)
           if (g == null || s == null)
               throw new ArgumentNullException();
           getter = g;
           setter = s;
       public T this[I index]
               return getter(index);
               setter(index, value);
Now, you can add multiple indexers to your class, but make sure you initialize the indexers properly. The following example demonstrates how to expose multiple indexers:
public class MyClass
       private List<string> myList = new List<string>();
       public MyClass()
           myList.AddRange(new string[]{"1","2","3"});
           // Init the IndexProperty with your methods (or lambdas)
           this.Keys=new IndexProperty<string,int>(
               i=> myList[i],
               (j,val)=> myList[j]=val);
       public IndexProperty<string,int> Keys { get; set; }
The following code demonstrates how your class can be used:
static void SampleMethod()
           MyClass c = new MyClass();
           c.Keys[0] = "value";


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Sion Cohen
Israel Israel
No Biography provided

Comments and Discussions

GeneralGood work around PinmemberDean Oliver25-Jan-12 18:55 
QuestionInteresting PinmemberPIEBALDconsult25-Jan-12 14:45 
AnswerRe: Interesting PinmemberSion Cohen25-Jan-12 22:50 
GeneralRe: Interesting PinmemberPIEBALDconsult26-Jan-12 2:08 
GeneralRe: Interesting PinmemberSion Cohen26-Jan-12 3:17 
GeneralRe: Interesting PinmemberPIEBALDconsult30-Jan-12 3:11 

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