How can I remove the output cache on a per-user basis in ASP.NET MVC?

Question

I'm using VaryByCustom to create an output cache on a per-browser and per-user basis:

[OutputCache(Duration = 6000, VaryByParam = "*", VaryByCustom="browser;userName")]

(I've overridden GetVaryByCustomString() to make this work.)

I need to be able to remove a single user's output cache, without invalidating the output cache of different users, if possible. I've read about HttpResponse.RemoveOutputCacheItem(), but that works by removing the output cache based on path. Is there any way to do this based on the VaryByCustom string?

Answer 1

You can take the advantage of VaryByCustom property in [OutputCache] by overriding HttpApplication.GetVaryByCustomString and check HttpContext.Current.User.IsAuthenticated.

This is what I will create in Global.asax.cs file:

public override string GetVaryByCustomString(HttpContext context, string custom)
    {
        if (custom == "UserName")
        {
            if (context.Request.IsAuthenticated)
            {
                return context.User.Identity.Name;
            }
            return null;
        }

        return base.GetVaryByCustomString(context, custom);
    }

And then use it in OutputCache attribute:

[OutputCache(Duration = 10, VaryByParam = "none", VaryByCustom = "UserName")]
public ActionResult Profiles()
{
    //...
}

but be careful that the username should be immutable in this case!