How can we implement singleton pattern in .net

The code below implicitly uses LazyThreadSafetyMode. Singleton classes are typically used in applications to create utility classes. A utility classes typically have the following characteristics. The Singleton Pattern should only be used when necessary as it can introduce a potential bottleneck for the application.

Sometimes, the pattern it may be viewed as an anti-pattern because it could introduce Global State. Global state , unknown dependencies within an application are introduced and it then becomes unclear as to how many types might depend on the information.

Additionally, many frameworks and repositories already limit access when required, so introducing an additional mechanism might limit the performance unnecessarily. Singleton Design Pattern C. Buy Now Read Review. WriteLine queueItem. About Latest Posts. Gary Woodfine. Technical Director at threenine. WriteLine "Singleton failed, variables contain different instances. Thread-safe Singleton To fix the problem, you have to synchronize threads during the first creation of the Singleton object.

Start ; process2. Start ; process1. Join ; process2. GetInstance value ; Console. WriteLine singleton. C Singleton The Singleton design pattern ensures a class has only one instance and provide a global point of access to it. Frequency of use:. C Prototype. C Adapter. UML class diagram. Structural code in C. There are suggestions that you can solve this problem with Dependancy Injection which you should also consider.

Singleton pattern is also one of the most commonly asked interview questions. Usually, candidates are asked to write one version of singleton implementation.

Now this will probably pass as a fine answer on an interview, but this code definitely has a lot of problems, apart from not being very impressive one. Yes, now you are using threads and Singleton and everyone will avoid you in the office. There it is, we used locks to make our singleton class thread-safe.

But, locks are not very good synchronization mechanisms in this case. Because the lock is required everytime Instance is asked for, the performance of this code will be degraded.

This problem can be avoided if we ask if the instance is null before locking and then asking is instance null once again after acquiring the lock. Now, that would look ugly. Also, we already have one if-null combo, and we can agree that controlling flow with if-null combos is not such a good idea and that it indicated that we have problems in our design.

Can we try to use the static constructor? Static constructors will assure that it has been run only once per application domain, meaning that our Singleton class can look like this:. The first thread that wants to get property Instance will trigger static constructor, also known as type initializer.