为什么“ resolve”方法总是调用已经在Unity中注册的类构造函数？

Question

I use Unity and Prism in my WPF application. I have a class that is registered to the Container in the Bootstrapper in this way:

Container.RegisterType<MyClass>();

The class has a constructor has ILoggerFacade interface as a parameter:

private ILoggerFacade _logger;

    public MyClass(ILoggerFacade logger)
    {
        _logger = logger;
        //do some stuff
    }

When I try to resolve that class instance, I realized that class constructor is called while returning the instance. So, all stuff is done from scratch. I resolve the instance this way:

MyClass a = Container.Resolve<MyClass>();

What is the reason behind calling constructor each Resolve method I execute?

Answer 1

If you doesn't want your component to be instancied at each resolve, you need to declare its lifetime as ContainerControlled :

myContainer.RegisterType<MySingletonObject>(new ContainerControlledLifetimeManager());

see https://msdn.microsoft.com/en-us/library/dn178463%28v=pandp.30%29.aspx#sec34 but be careful of side effects, as your object will behave like a singleton

Answer 2

Unity uses the transient lifetime manager by default (when you do not specify another lifetime manager). The transient lifetime manager will give you a NEW instance of the registered type each time you call resolve. There are other lifetime managers that can be specified during registration that will provide different behavior (singleton, etc.)