Singleton: create instance inside static constructor [duplicate]

Question

I was reading about Singleton design pattern when i come across this implementation:

public class Singleton
{
    private static Singleton Instance { get; private set; }

    private Singleton()
    {
    }

    static Singleton()
    {
        Instance = new Singleton();
    }
}

Is this singleton thread safe? What are pros and cons of such implementation?

For discussion of pros/cons (which are mostly off-topic on Stack Overflow), see e.g. csharpindepth.com/Articles/General/Singleton.aspx — Peter Duniho
– Peter Duniho, Commented Feb 15, 2017 at 19:26
Your example is functionally identical to simply initializing the backing field directly, e.g. static Singleton Instance { get; } = new Singleton();, a variation that is discussed in the article. Of course, the code you posted is useless, because the Instance property is private, and so can only be called by the Singleton class itself (which has no constraints on how many instances of Singleton it can create...singletons are really only useful constructs for outside code). — Peter Duniho
– Peter Duniho, Commented Feb 15, 2017 at 19:36

Casey O'Brien · Accepted Answer · 2017-02-15 19:20:07Z

0

No singletons are not thread safe, I would recommend reading https://msdn.microsoft.com/en-us/library/ff650316.aspx

answered Feb 15, 2017 at 19:20

Casey O'Brien

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1 Comment

Peter Duniho Over a year ago

The singleton initialization the OP is asking about is thread-safe. Of course, whether the singleton object itself is thread-safe is a completely separate matter. Though, it'd be very bad form to write a singleton object that isn't thread-safe in a context where thread-safety is in any way an issue, since by its very nature, a singleton is used repeatedly and potentially concurrently.

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