A singleton class example in C#.

SingletonPatternExample.cs

public sealed class SingletonExample
{
  // internal singleton instance
  private static SingletonExample _instance;

  // lock for thread-safety laziness
  private static readonly object _mutex = new object();

  // private empty constuctor
  private SingletonExample()
  {
  }

  // public method, used to obtain an instance of this class
  // implements double-locking
  public static SingletonExample Instance
  {
    get
    {
      if (_instance == null)
      {
        lock (_mutex)
        {
          if (_instance == null)
          {
            _instance = new SingletonExample();
          }
        }
      }

      return _instance;
    }
  }
}

so can use Instance in any class in the common namespace now?