Accessing a Collection

Question

I'm trying to make a class where you can access a collection in it and get an item using a string index, (I hope this makes sense), basically I would like to know either what this is called or how to do it?

here is an example of what I mean;

string blah = SomeClass.Items["Item1"].ToString();

Hopefully someone can make some sense of this.

Thank You.

I guess it makes sense but how do you determine what the string name is? You can make your indexers do and return anything you want. — Jeff Mercado, May 20 '12 at 18:34
It's probably a `Dictionary`. Or you can implement your own collection. The indexer (the square brackets) is implemented as the 'this' property. See http://stackoverflow.com/questions/287928/how-do-i-overload-the-square-bracket-operator-in-c — Roger Lipscombe, May 20 '12 at 18:35

David Heffernan · Accepted Answer · 2012-05-20T18:40:36.597

I think you are looking for an indexer.

Indexers allow instances of a class or struct to be indexed just like arrays. Indexers resemble properties except that their accessors take parameters.

In your case you want to index using a string. Something like this:

public MyItem this[string index]
{
    get { return ... }
}

It may be that you would be better off removing the Items layer from your syntax. That would result in your code reading like this:

string blah = SomeClass["Item1"].ToString();

score 1 · Answer 2 · answered May 20 '12 at 18:34

1

You mean a string indexer.

Indexers allow instances of a class or struct to be indexed just like arrays. Indexers resemble properties except that their accessors take parameters.

answered May 20 '12 at 18:34

Oded

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score 0 · Answer 3 · answered May 20 '12 at 18:34

0

Use a Dictionary<string, string>.

answered May 20 '12 at 18:34

Yuriy Faktorovich

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Chris Gessler · Answer 4 · 2012-05-20T18:44:06.977

You can use a wrapper around a List to get the "Items" property.

public class MyClass
{

  private readonly List<string> _myColl = new List<string>();

  public List<string> Items
  { 
    get { return this._myColl; }
  }

}

You can then use it like so:

MyClass c = new MyClass();
c.Items.Add("something");

If you need a string key, you can always switch List to Dictionary<string, string>

public class MyClass
{

  private readonly Dictionary<string, string> _myColl = new Dictionary<string, string>();

  public Dictionary<string, string> Items
  { 
    get { return this._myColl; }
  }

}

Then use it like so:

MyClass c = new MyClass();
c.Items.Add("somekey", "somevalue");

I guess the point is that you can wrap just about any collection with this pattern to fit almost any need.

score 0 · Answer 5 · answered May 20 '12 at 18:36

0

As people have said, an indexed property is one option. Tutorial here

http://msdn.microsoft.com/en-us/library/aa288464(v=vs.71).aspx

answered May 20 '12 at 18:36

Charleh

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Accessing a Collection

5 Answers5