如何在 ASP.NET Web API v2 中自动实例化对象（单例）？

Question

I'm loading a large object in memory into a singleton for reuse between GET requests. However when the application starts I want the singleton to initialize automatically, currently I have something like this

    public HttpResponseMessage GetData([FromBody]string text)
    {
        var spc = MySingleton.Instance; //runs some long instantiation process on the first call
        …
    }

So I have to wait until a request comes in before the singleton gets initialized. Is there a way to make the singleton object initialize on its own when I start the application?

I tried putting this line

var spc = MySingleton.Instance;

In the Application_Start() method of global.asax.cs but it didn't do anything.

Answer 1

Trying use Dependency Injection, hopefully the IOC container will create your configured instance of the singleton object before your first request.

In Startup.cs , in the ConfigureServices method you will add something like:

public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<ISingleton, Singleton>();
}

From this Singleton pattern tutorial here .

In your controller that has the method GetData you will change the default constructor from parameter-less to having the Singleton object be a required argument to instantiate that controller. The .NET Core IOC container will take care of instantiating the controller passing your singleton instance configured in in Startup.ConfigureServices .