Add Singleton design pattern

Author: ElliotOne

CSharpDesignPatterns.sln

@@ -31,6 +31,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Strategy", "Behavioral\Stra
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Visitor", "Behavioral\Visitor\Visitor.csproj", "{32E13EA5-C3A3-4DC9-9F2C-B938C7632320}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Singleton", "Creational\Singleton\Singleton.csproj", "{DF0DD259-1E2B-4385-922D-90E782C00106}"
+EndProject
 Global
 GlobalSection(SolutionConfigurationPlatforms) = preSolution
 Debug|Any CPU = Debug|Any CPU
@@ -81,6 +83,10 @@ Global
 {32E13EA5-C3A3-4DC9-9F2C-B938C7632320}.Debug|Any CPU.Build.0 = Debug|Any CPU
 {32E13EA5-C3A3-4DC9-9F2C-B938C7632320}.Release|Any CPU.ActiveCfg = Release|Any CPU
 {32E13EA5-C3A3-4DC9-9F2C-B938C7632320}.Release|Any CPU.Build.0 = Release|Any CPU
+{DF0DD259-1E2B-4385-922D-90E782C00106}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+{DF0DD259-1E2B-4385-922D-90E782C00106}.Debug|Any CPU.Build.0 = Debug|Any CPU
+{DF0DD259-1E2B-4385-922D-90E782C00106}.Release|Any CPU.ActiveCfg = Release|Any CPU
+{DF0DD259-1E2B-4385-922D-90E782C00106}.Release|Any CPU.Build.0 = Release|Any CPU
 EndGlobalSection
 GlobalSection(SolutionProperties) = preSolution
 HideSolutionNode = FALSE
@@ -97,6 +103,7 @@ Global
 {A88078BD-72BC-42B3-B834-1DC4B54F78BE} = {5CD94193-53CA-4778-A0AC-316420C95287}
 {74531DF4-FF3D-437C-AE03-775F0EBBE1E4} = {5CD94193-53CA-4778-A0AC-316420C95287}
 {32E13EA5-C3A3-4DC9-9F2C-B938C7632320} = {5CD94193-53CA-4778-A0AC-316420C95287}
+{DF0DD259-1E2B-4385-922D-90E782C00106} = {5059E893-546D-4C2A-95CA-9290FA8BE064}
 EndGlobalSection
 GlobalSection(ExtensibilityGlobals) = postSolution
 SolutionGuid = {7A564543-B6AA-4CF1-940C-AF2C1DEFAF1A}

Creational/Singleton/Program.cs

@@ -0,0 +1,20 @@
+using System;
+
+namespace Singleton
+{
+ class Program
+ {
+ static void Main(string[] args)
+ {
+ var singleton1 = Singleton.Instance();
+ var singleton2 = Singleton.Instance();
+
+ if (singleton1 == singleton2)
+ {
+ Console.WriteLine("Objects are the same instance!");
+ }
+
+ Console.ReadKey();
+ }
+ }
+}

Creational/Singleton/Singleton.cs

@@ -0,0 +1,16 @@
+namespace Singleton
+{
+ public sealed class Singleton
+ {
+ private static Singleton _instance;
+
+ private Singleton()
+ {
+ }
+
+ public static Singleton Instance()
+ {
+ return _instance ?? (_instance = new Singleton());
+ }
+ }
+}

Creational/Singleton/Singleton.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+ <PropertyGroup>
+ <OutputType>Exe</OutputType>
+ <TargetFramework>net5.0</TargetFramework>
+ </PropertyGroup>
+
+</Project>