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c#asp.netasp.net-corehttpcontext

Why should I inject IHttpContextAccessor as a Singleton

In all examples that i've seen of IHttpContextAccessor injection, it is set as a Singleton.

Examples:

How to add IHttpContextAccessor in the Startup class in the DI in ASP.NET Core 1.0? Injecting IHttpContextAccessor into ApplicationDbContext ASP.NET Core 1.0 .NET Core IHttpContextAccessor issue

I find it kinda weird, since HttpContext really looks like something that maps to requests. Wouldn't AddScoped be more appropriate in this case?

Is Singleton really the recomended way? Am I not seeeing something?

Solution

  • Is Singleton really the recomended way?

    Yes

    According to comments associated with an issue raised on GitHub

    https://github.com/aspnet/Hosting/issues/793#issuecomment-224828588

    In that sample, you are registering it as a singleton. Shouldn't it be a scoped instance?

    It's fine being a singleton because the backing store is async local.

    Which got a later reply

    https://github.com/aspnet/Hosting/issues/793#issuecomment-224924030

    Actually if you register it as a Transient on .NET Core then it doesn't work properly since the implementation for .NET Core is using a AsyncLocal which relies upon the instance variable to track the thread local storage slot. So it has to be registered as a singleton on .NET Core.