PROGRAMMING IN C#

Collection Classes (C# Programming Guide)

The .NET Framework provides specialized classes for data storage and retrieval. These classes provide support for stacks, queues, lists, and hash tables. Most collection classes implement the same interfaces, and these interfaces may be inherited to create new collection classes that fit more specialized data storage needs.

ArrayList list = new ArrayList(); list.Add(10);

list.Add(20);

Collection Classes Overview

Collection Classes have the following properties Collection classes are defined as part of

the System.Collections or System.Collections.Generic namespace. Most collection classes derive from the

interfaces ICollection, IComparer, IEnumerable, IList, IDictionary, and IDictionaryEnumerator and their generic equivalents.

Generic collection classes provide increased type-safety and in some cases can provide better performance, especially when they store value types

Generics

Generics were added to version 2.0 of the C# language and the common language runtime (CLR). Generics introduce to the .NET Framework the concept of type parameters, which make it possible to design classes and methods that defer the specification of one or more types until the class or method is declared and instantiated by client code. For example, by using a generic type parameter T you can write a single class that other client code can use without incurring the cost or risk of runtime casts or boxing operations, as shown here:

Generics

Structs 

Structs share most of the same syntax as classes, although structs are more limited than classes:

Within a struct declaration, fields cannot be initialized unless they are declared as const or static.

A struct cannot declare a default constructor (a constructor without parameters) or a destructor.

Structs are copied on assignment. When a struct is assigned to a new variable, all the data is copied, and any modification to the new copy does not change the data for the original copy. This is important to remember when working with collections of value types such as Dictionary<string, myStruct>.

Structs are value types and classes are reference types. Unlike classes, structs can be instantiated without using a new operator. Structs can declare constructors that have parameters. A struct cannot inherit from another struct or class, and it cannot be the base of a

class. All structs inherit directly from System.ValueType, which inherits from System.Object.

A struct can implement interfaces. A struct can be used as a nullable type and can be assigned a null value.

Structs 

A struct type is a value type that is typically used to encapsulate small groups of related variables, such as the coordinates of a rectangle or the characteristics of an item in an inventory. The following example shows a simple struct declaration:

public struct Book { public decimal price; public string title; public string author; }

Iterators (C# Programming Guide)

An iterator is a method, get accessor, or operator that performs a custom iteration over an array or collection class by using the yield keyword. The yield return statement causes an element in the source sequence to be returned immediately to the caller before the next element in the source sequence is accessed. Although you write an iterator as a method, the compiler translates it into a nested class that is, in effect, a state machine. This class keeps track of the position of the iterator as long the foreach loop on the client code continues