AspNetCore.Docs/aspnetcore/security/authorization/dependencyinjection.md

title	author	description	ms.author	ms.date	no-loc	uid
Dependency injection in requirement handlers in ASP.NET Core	rick-anderson	Learn how to inject authorization requirement handlers into an ASP.NET Core app using dependency injection.	riande	10/14/2016	Kestrel appsettings.json ASP.NET Core Identity cookie Cookie Blazor Blazor Server Blazor WebAssembly Identity Let's Encrypt Razor SignalR	security/authorization/dependencyinjection

Dependency injection in requirement handlers in ASP.NET Core

Authorization handlers must be registered in the service collection during configuration using dependency injection.

Suppose you had a repository of rules you wanted to evaluate inside an authorization handler and that repository was registered in the service collection. Authorization resolves and injects that into the constructor.

For example, to use ASP.NET's logging infrastructure, inject ILoggerFactory into the handler. Such a handler might look like the following code:

public class LoggingAuthorizationHandler : AuthorizationHandler<MyRequirement>
   {
       ILogger _logger;

       public LoggingAuthorizationHandler(ILoggerFactory loggerFactory)
       {
           _logger = loggerFactory.CreateLogger(this.GetType().FullName);
       }

       protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, MyRequirement requirement)
       {
           _logger.LogInformation("Inside my handler");
           // Check if the requirement is fulfilled.
           return Task.CompletedTask;
       }
   }

The preceding handler can be registered with any service lifetime. The following code uses AddSingleton to register the preceding handler:

services.AddSingleton<IAuthorizationHandler, LoggingAuthorizationHandler>();

An instance of the handler is created when the app starts, and DI injects the registered ILoggerFactory into the constructor.

[!NOTE] Handlers that use Entity Framework shouldn't be registered as singletons.