Singleton

Singleton

• + we can use singletons as parameters
• + control over instantion

Static class

• - lazy initialization
• + easier

• Standard solution using locks.

public sealed class Singleton
{
    static Singleton _instance=null;
    static readonly object _lock = new object();
 
    Singleton()
    {
    }
 
    public static Singleton Instance
    {
        get
        {
            lock (_lock)
            {
                if (_instance==null)
                {
                    _instance = new Singleton();
                }
                return _instance;
            }
        }
    }
}

• Elegant solution without locks.

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

• Solves complications if one static constructor invokes another which invokes the first again. Solution breaks the cycle.

public sealed class Singleton
{
    Singleton()
    {
    }
 
    public static Singleton Instance
    {
        get
        {
            return Nested.instance;
        }
    }
 
    class Nested
    {
        static Nested()
        {
        }
 
        internal static readonly Singleton instance = new Singleton();
    }
}

• http://www.yoda.arachsys.com/csharp/singleton.html
• http://dotnet.dzone.com/news/c-singleton-pattern-vs-static-