>What's a Singleton? An example would be nice?


Here is an example. I hear this was one of the most over used patterns but there are times when this is the best way to keep from having multiple instances of a class. For a good example, I often work with devices such as a Gps or an RFID reader. The class that talks to the device can only have a single instance because there can only be a single connection to the port the device is on. However I often need to subscribe to the events from the device class from multilple places. So I use a singleton pattern to always just get the instance of the existing class if it already exists. It looks like this:

public class GpsWrapper : System.ComponentModel.Component
{

#region Singleton

private static GpsWrapper instance = null;
public static GpsWrapper Instance
{
     get
     {
          if(instance == null)
               instance = new GpsWrapper();

          return instance;
     }
}

/// <summary>
/// Constructor
/// Private due to Singleton use
/// </summary>
private GpsWrapper()
{
     this.Initialize();
}

#endregion Singleton

Notice the constructor is private so it can't be called from outside the class. When a class makes a call to this it references the singleton like this:

GpsWrapper Gps = GpsWrapper.Instance;

If the Gps already exists, the existing instance is passed back, otherwise it is created first.

I hope that helps
Tim