Role:
The purpose of the Singleton pattern is to ensure that there is only one instance of a class, and that there is a global access point to that object.
Design:
- Make the constructor private and add a private static constructor as well.
- Add a private static read-only object that is internally instantialed using the private constructor.
- Add a public static property that accesses the private object.
Implementation:
public sealed class Singleton
{
// Private constructor.
private Singleton()
{
Console.WriteLine("One instance is created.");
} // private object instantiated with private constructor.
private static readonly Singleton instance = new Singleton(); // Public static property to get the object.
public static Singleton UniqueInstance
{
get
{
return instance;
}
}
}
class Program
{
static void Main(string[] args)
{
Singleton s0 = Singleton.UniqueInstance;
Singleton s1 = Singleton.UniqueInstance;
Singleton s2 = Singleton.UniqueInstance;
}
}