Design Patterns---singleton patterns in. Net

. NET Design Patterns:

NET design Pattern Example Singleton pattern (Singleton pattern)

One: Introduction to the Singleton mode: (Brief Introduction)

Singleton mode (Singleton pattern), which guarantees that a class has only one instance, and provides a global access point to access it. Singleton mode because Singleton encapsulates its only instance, it can strictly control how a customer accesses it and when to access it. Simply said is a single mode: Only you can have a person to visit;

Ii. Problem Solving (what to Solve)

Consider using singleton mode when a class allows only one instance to be created.

Three single-Case Pattern analysis ( Analysis )

Singleton class , which defines a private variable instance; Private constructor Method Singleton () and Method getinstance ();

Private variable instance:

Singleton pattern Structure:

private static Singleton instance;

Private constructor Method Singleton (), you cannot use the New keyword to create an instance of this class.

Private Singleton ()

{

}

Method getinstance (), which is the only global access point for an instance of this class.

public static Singleton getinstance ()

{

If the instance does not exist, then new instance is returned, otherwise an existing instance

if (instance = = null)

{

Instance = new Singleton ();

}

return instance;

}

Singleton Pattern Code

1, single case mode class singleton

public class Singleton { private static Singleton instance; <summary> Create a static read-only process helper when the program is running </summary> private static readonly Object _object = new Object (); <summary> The constructor method is private, and the foreign key cannot instantiate this class through the new class </summary> Private Singleton () { } <summary> This method is the only global access point for this class of instances (Double plus lock double-check Locking) </summary> <returns></returns> public static Singleton getinstance () { First determine if the instance exists, there is no additional lock processing if (instance = = null) { The part of the program with the lock at the same time has only one thread to enter, Lock (_object) { If the instance does not exist, then new instance is returned, otherwise an existing instance if (instance = = null) { Instance = new Singleton (); } } } return instance; } }

2 , client-side code

static void Main (string[] args) { Singleton Singleton2 = Singleton.getinstance (); Singleton Singleton3 = Singleton.getinstance (); if (Singleton2 ==singleton3) { Console.WriteLine ("Instance Singleton2 is the same as instance Singleton3! "); } Console.readkey (); }

The singleton pattern can also be used without shackles, such as using the three-layer technology call class in a class:

#region get its own singleton mode: UserInfo represents the class file in the BLL layer

private static UserInfo instance;

public static UserInfo getinstance ()

{

if (instance==null)

{

Instance = new UserInfo ();

}

return instance;

}

#endregion

Called in the presentation layer:

. Bll. UserInfo BLL = BLL. Userinfo.getinstance ();

Design Patterns---singleton patterns in. Net