Question

What do you guys think about this for a generic singleton?

using System; using System.Reflection;  // Use like this /* public class Highlander : Singleton<Highlander> {     private Highlander()     {         Console.WriteLine('There can be only one...');     } } */  public class Singleton<T> where T : class {     private static T instance;     private static object initLock = new object();      public static T GetInstance()     {         if (instance == null)         {             CreateInstance();         }          return instance;     }      private static void CreateInstance()     {         lock (initLock)         {             if (instance == null)             {                 Type t = typeof(T);                  // Ensure there are no public constructors...                 ConstructorInfo[] ctors = t.GetConstructors();                 if (ctors.Length > 0)                 {                    throw new InvalidOperationException(String.Format('{0} has at least one accesible ctor making it impossible to enforce singleton behaviour', t.Name));                 }                  // Create an instance via the private constructor                 instance = (T)Activator.CreateInstance(t, true);             }         }     } } 

Answer 1

Creating a singleton class is just a few lines of code, and with the difficulty of making a generic singleton i always write those lines of code.

public class Singleton {     private Singleton() {}     static Singleton() {}     private static Singleton _instance = new Singleton();     public static Singleton Instance { get { return _instance; }} } 

The

private static Singleton _instance = new Singleton(); 

line removes the need for locking, as a static constructor is thread safe.