The indexer in C#(C#中的索引器)

Indexers allow instances of a class or struct to be indexed just like arrays. Indexers resemble 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 of assigning and retrieving values. The Program class creates an instance of this class for storing strings.

class SampleCollection<T>

// This class shows how client code uses the indexer.
class Program
//declaration:
class Mlass

//usage:
Mlass m = new Mlass();
m[2, 2] = 3;
Console.WriteLine(m[2, 2]);

Addition

1. Just like any other class members, indexers can also participate in inheritance. A base class indexer is inherited to the derived class.

2. A Base class indexer can be polymorphicaly overridden in a Derived class. But remember that the modifiers like virtual, override etc are using at property level, not at accessor level.

3. An indexer inside a class can be declared as abstract by using the keyword abstract. Remember that an abstract indexer in a class carries no code at all. The get/set accessors are simply represented with a semicolon. In the derived class we must implement both set and get assessors.

　　If the abstract class contains only set accessor, we can implement only set in the derived class.

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