Question

Can anyone help me to understand the benefit of using System.Lazy with Singleton Design Pattern.

Answer 1

The best source on C# Singletons (also covers Lazy<>) belongs to Jon Skeet: http://csharpindepth.com/Articles/General/Singleton.aspx

Suppose you want to have a class that :

• represents a unique resource, so it should have a unique instance,
• the instance needs an expensive initialization,
• the initialization parameters will be available only at the run-time,
• there are cases which you will not use the object after all,
• there are more than one threads that could try to initialize the singleton object simultaneously,
• etc.

If most of the above conditions are true, you will need to ensure that the class is Singleton, and the unique instance is lazily initialized (not initialized until needed) If you target C# 4.0 or later, using Lazy<> makes your design simpler, more readable and easier to remember.