One, Singleton mode (Singleton)

The initial definition of the singleton pattern appears in design mode (Eddisonvis, 1994): "Guarantees that a class has only one instance, and provides a global access point to access it." ”

Features: First, there can only be one instance of a class;

The second is that it must create this instance on its own;

Thirdly, it must provide this instance to the whole system on its own.

First, the classic realization

usingSystem;namespacesingletonpattern{//Classic notation//sealed prevent other classes from inheriting from this class     Public Sealed classClassicalsample {//used to save unique instances        Private Staticclassicalsample _classicalsample; //Lock Range        Private Static ReadOnly Objectobj =New Object(); //private constructors to prevent external new instantiation        PrivateClassicalsample () {Console.WriteLine ("instantiation of"); }        //unify this class of         Public Staticclassicalsample getinstance () {//reduce the cost of locks            if(_classicalsample = =NULL)            {                //Prevent multithreading concurrency                Lock(obj) {//                     if(_classicalsample = =NULL) {_classicalsample=Newclassicalsample (); }}} Console.WriteLine ("Get Instance"); return_classicalsample; }    }}

Second, the static constructor implementation

usingSystem;namespacesingletonpattern{ Public Sealed classStaticconstructorsample {Private Staticstaticconstructorsample _staticconstructorsample; PrivateStaticconstructorsample () {Console.WriteLine ("instantiation of"); }        //Static constructors: Executes at first use and executes only once        Staticstaticconstructorsample () {_staticconstructorsample=Newstaticconstructorsample (); Console.WriteLine ("Static constructor instantiation"); }         Public Staticstaticconstructorsample getinstance () {Console.WriteLine ("Get Instance"); return_staticconstructorsample; }    }}

Third, static variable implementation

usingSystem;namespacesingletonpattern{ Public Sealed classStaticvariablesample {Private Static ReadOnlyStaticvariablesample _staticvariablesample =Newstaticvariablesample (); PrivateStaticvariablesample () {Console.WriteLine ("instantiation of"); }         Public Staticstaticvariablesample getinstance () {Console.WriteLine ("Get Instance"); return_staticvariablesample; }    }}

Test:

usingSystem;usingSystem.Collections.Generic;usingSystem.Linq;usingSystem.Threading.Tasks;namespacesingletonpattern{classProgram {Static voidMain (string[] args)            {classicalsampletest ();            Staticconstructorsampletest ();            Staticvariablesampletest ();        Console.read (); }        Static voidClassicalsampletest () {Console.WriteLine ("Classic single-case mode test"); TaskFactory TaskFactory=NewTaskFactory (); //task groups for multithreaded testinglist<task> tasks =NewList<task>(); //Each thread gets the instance setlist<classicalsample> list =NewList<classicalsample>();  for(inti =0; I < -; i++) {tasks. ADD (Taskfactory.startnew<ClassicalSample> (() = Classicalsample.getinstance ()). ContinueWith ((r) ={list.                ADD (R.result);            })); } taskfactory.continuewhenall (Tasks. ToArray (), p={Console.WriteLine (""); Console.WriteLine ("a total of {0} occurrences were obtained after the tasks group execution was completed", P.count ()); Console.WriteLine ("number of instances {0}", List. Distinct ().            Count ());        }); }        Static voidStaticconstructorsampletest () {Console.WriteLine ("Static constructor Single-instance mode test"); TaskFactory TaskFactory=NewTaskFactory (); //task groups for multithreaded testinglist<task> tasks =NewList<task>(); //Each thread gets the instance setlist<staticconstructorsample> list =NewList<staticconstructorsample>();  for(inti =0; I < -; i++) {tasks. ADD (Taskfactory.startnew<StaticConstructorSample> (() = Staticconstructorsample.getinstance ()). ContinueWith ((r) ={list.                ADD (R.result);            })); } taskfactory.continuewhenall (Tasks. ToArray (), p={Console.WriteLine (""); Console.WriteLine ("a total of {0} occurrences were obtained after the tasks group execution was completed", P.count ()); Console.WriteLine ("number of instances {0}", List. Distinct ().            Count ());        }); }        Static voidStaticvariablesampletest () {Console.WriteLine ("static variable single-case mode test"); TaskFactory TaskFactory=NewTaskFactory (); //task groups for multithreaded testinglist<task> tasks =NewList<task>(); //Each thread gets the instance setlist<staticvariablesample> list =NewList<staticvariablesample>();  for(inti =0; I < -; i++) {tasks. ADD (Taskfactory.startnew ()= Staticvariablesample.getinstance ()). ContinueWith ((r) ={list.                ADD (R.result);            })); } taskfactory.continuewhenall (Tasks. ToArray (), p={Console.WriteLine (""); Console.WriteLine ("a total of {0} occurrences were obtained after the tasks group execution was completed", P.count ()); Console.WriteLine ("number of instances {0}", List. Distinct ().            Count ());        }); }    }}

One, Singleton mode (Singleton)