Does .net core dependency injection support Lazy<T>

Question

I am trying to use the generic Lazy class to instantiate a costly class with .net core dependency injection extension. I have registered the IRepo type, but I'm not sure what the registration of the Lazy class would look like or if it is even supported. As a workaround I have used this method http://mark-dot-net.blogspot.com/2009/08/lazy-loading-of-dependencies-in-unity.html

config:

public void ConfigureService(IServiceCollection services) {     services.AddTransient<IRepo, Repo>();     //register lazy } 

controller:

public class ValuesController : Controller  {     private Lazy<IRepo> _repo;      public ValuesController (Lazy<IRepo> repo)     {         _repo = repo;     }      [HttpGet()]     public IActionResult Get()     {          //Do something cheap          if(something)              return Ok(something);          else              return Ok(repo.Value.Get());     } } 

Answer 1

Here's another approach which supports generic registration of Lazy<T> so that any type can be resolved lazily.

services.AddTransient(typeof(Lazy<>), typeof(Lazier<>));  internal class Lazier<T> : Lazy<T> where T : class {     public Lazier(IServiceProvider provider)         : base(() => provider.GetRequiredService<T>())     {     } } 

Answer 2

You only need to add a registration for a factory method that creates the Lazy<IRepo> object.

public void ConfigureService(IServiceCollection services) {     services.AddTransient<IRepo, Repo>();     services.AddTransient<Lazy<IRepo>>(provider => new Lazy<IRepo>(provider.GetService<IRepo>)); }