Singleton is a creational design pattern, which ensures that only one object of its kind exists and provides single point of access to it for any other code.
Singleton has almost the same pros and cons as global variables. Although they are super-handy, they break modularity of your code.
You can just use a class, which depends on Singleton, in some other context. You'll have to carry the Singleton class as well. Most of the time, this limitation comes up during the creation of unit tests.
Application of the pattern in C#
Usage examples: A lot of developers consider the Singleton pattern an antipattern. That's why its usage is on the decline in C# code.
Identification: Singleton can be recognized by a static creational method, which returns same cached object.
Example: Structure of the Pattern
This example illustrates the structure of the Singleton design pattern. It focuses on answering these questions:
- What classes does it consists of?
- What roles do these classes play?
- In what way the elements of the pattern are related?