What's the correct way to have Singleton class in c# [duplicate]

问题

I am learning Singleton design pattern in C#, and I have written below code in two ways, and I want to know Which one is the right way to create a Singleton class:

public sealed class TranslationHelper
{
    // first way
    private static readonly TranslationHelper translationHelper = new TranslationHelper();
    // second way
    public static readonly TranslationHelper translationHelpers = new TranslationHelper(); // Direct call

    public static TranslationHelper GetTranslationHelper()
    {
        return translationHelper;
    }

    private TranslationHelper()
    {
    }
}

CALL:

TranslationHelper instance = TranslationHelper.GetTranslationHelper();
TranslationHelper ins = TranslationHelper.translationHelpers;

I am beginner so I am not sure if both methods are same. Please guide me.

回答1:

If you are using .Net 4 or higher you can use the Lazy<T> type like this:

public sealed class Singleton
{
    private static readonly Lazy<Singleton> lazy =
        new Lazy<Singleton>(() => new Singleton());

    public static Singleton Instance { get { return lazy.Value; } }

    private Singleton()
    {
    }
}

By using this design pattern with a private constructor you are insuring that the class and it is only created at the time it is used. This is ensured because

It can only be called by itself so it does not get instantiated ahead of time.
The Lazy<T> keyword when used with the private static readonly lambda function now provides a visually clear way of lazily creating an instance of the class from within the function itself.
The public Singleton Instance property provides a way to access that singleton from outside the class.

来源：https://stackoverflow.com/questions/52173966/whats-the-correct-way-to-have-singleton-class-in-c-sharp

标签

.net

design-patterns