public sealed class Singleton
{
private Singleton() {}
private static volatile Singleton _value;
private static object syncRoot = new Object();
public static Singleton Value
{
get
{
if (_value == null )
{
lock (syncRoot)
{
if (_value == null )
{
_value = new Singleton();
} //end inner if
} //end lock
} //end outer if
return _value;
} //end get
} //end Value
} //end class
• Double-check locking is used to ensure that exactly one instance is ever created and only when needed
• syncRoot is used to lock on rather than locking on the type itself to avoid deadlocks caused by outside code
• The _value instance is declared to be volatile in order to assure that the assignment to _value and any writes inside the Singleton constructor complete before the instance can be accessed