What is the Singleton pattern?

The Singleton pattern guarantees that a class has only one instance and provides a global point of access to that instance.

In C#, this is usually implemented through a private constructor and a static property that creates and stores the single object:

public sealed class Singleton
{
    private static readonly Singleton _instance = new Singleton();

    // Private constructor prevents external instantiation
    private Singleton() { }

    public static Singleton Instance
    {
        get { return _instance; }
    }

    public void SomeMethod()
    {
        // Method logic
    }
}

This approach ensures lazy initialization and thread safety (if other implementation options are used). Singleton is useful when a single shared resource is needed, such as configuration or connection manager.