Just think of it a short-cut way of accessing a member of a collection. If you saw the example I posted earlier and added a method:

public  Invoice GetInvoice( string s)
        {
            return Invoices.Find(x => x.Id == s);
        }

then you could get an instance from the collection using either of these methods:

Invoice i = InvoiceList.GetInvoice("A1234");
Invoice x = InvoiceList["A1234"];

the idea being that the second version is more concise....



>Truth is, I don't really know what I'm asking. I'm trying to understand the point behind an indexer. On the surface it appears to be nothing more than a collection attached to a class. But I don't see why you would use one when you can create a collection as a property.
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>>Hi,
>>Sorry, that makes no sense to me. Can you explain more how you envisage that working?
>>
>>>I think I may havee a good use for an indexer:
>>>
>>>Assume I create a Customer class. It has a RecordKey property and a LoadData method. If Recordkey is set to a key value and LoadData is called, then the class is loaded for that customer.
>>>
>>>If Recordkey is set to a 0 and LoadData is called, then the class's indexer is used to load all customers.
>>>
>>>Anyone?
>>>
>>>
>>>
>>>>Does this help? http://stackoverflow.com/questions/609594/what-is-the-use-of-indexers
>>>>
>>>>>I have this customer class:

>public class Customer
>>>>>{
>>>>>    private List<Invoice> _Invoices = new List<Invoice>();
>>>>>    public Invoice this[int item]
>>>>>    {
>>>>>        get
>>>>>        {
>>>>>            return _Invoices[item];
>>>>>        }
>>>>>        set
>>>>>        {
>>>>>            _Invoices[item] = value;
>>>>>        }
>>>>>    }
>>>>>}

>I then do this:

>static void Main(string[] args)
>>>>>{
>>>>>    Invoice InvA = new Invoice();
>>>>>    InvA.InvoiceId = "A0001";
>>>>>
>>>>>    Invoice InvB = new Invoice();
>>>>>    InvB.InvoiceId = "B0002";
>>>>>
>>>>>    Customer cust = new Customer();
>>>>>    cust[0] = InvA;
>>>>>    cust[1] = InvB;
>>>>>}>

>I'm not really seeing a usage for indexers. It seems to me that an Invoices collection would be better. What's the point of indexers?