Indexers (C# Programming Guide)
Indexers permit instances of a class or struct to be indexed in the same way as arrays. Indexers are similar to properties except that their accessors take parameters.
In the following example, a generic class is defined and provided with simple get and set accessor methods as a means for assigning and retrieving values. The class Program creates an instance of this class for storing strings.
class SampleCollection<T> { private T[] arr = new T[100]; public T this[int i] { get { return arr[i]; } set { arr[i] = value; } } } // This class shows how client code uses the indexer class Program { static void Main(string[] args) { SampleCollection<string> stringCollection = new SampleCollection<string>(); stringCollection[0] = "Hello, World"; System.Console.WriteLine(stringCollection[0]); } }
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Indexers enable objects to be indexed in a similar way to arrays.
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A get accessor returns a value. A set accessor assigns a value.
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The this keyword is used to define the indexers.
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The value keyword is used to define the value being assigned by the set indexer.
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Indexers do not have to be indexed by an integer value; it is up to you how to define the specific look-up mechanism.
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Indexers can be overloaded.
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Indexers can have more than one formal parameter, for example, when accessing a two-dimensional array.
For more information, see the following sections in the C# Language Specification:
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1.6.6.3 Indexers
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10.2.7.3 Member names reserved for indexers
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10.8 Indexers
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13.2.4 Interface indexers
