ASP.NET中的Per-Request静态数据

Question

I'm wanting to cache the roles a user is in for each request that comes in. There are several places throughout any given page where where we have something like:

<% if(Roles.IsUserInRole("RoleName")) {%>
    <!-- Conditional Rendering -->
<% } else if(Roles.IsUserInRole("AnotherRole") {%>
    <!-- You get the point -->
<% } %>

Since this is all stored in a sql database, each of these requests hit the database. I know there are ways to cache the roles in a cookie, but I don't want to do that. Anyway, What I was thinking was something like this.

public static class SecurityUtils
    {
        public static string[] UserRoles()
        {
            var context = HttpContext.Current;

            if (context == null) return Enumerable.Empty<string>();

            string[] roles;

            roles = context.Items["UserRoles"] as string[];

            if (roles == null)
            {
                roles = Roles.GetRolesForUser();
                context.Items["UserRoles"] = roles;
            }

            return roles;
        }
    }

Anyone see any issues with this? I know that ever call to UserRoles() will lookup the item in the context and maybe this isn't the most effecient thing to do. What I really want to know is if this will cache it on a per-request basis so there's no overlap with other users request.

Answer 1

That looks safe enough at a quick glance. HttpContext.Current.Items is a per-HTTP request cache. Another option to consider to further reduce database calls would be to use session state.

Consider a scenario where you have a page with a lot of ajax stuff going on. Each ajax request will invoke a database call to load security roles, since they are all separate HTTP requests.

Answer 2

It will cache it per request, since you are using the current HttpContext .

If you were using a static member, it would be cached till the web application was recycled.

As such it looks fine - a fairly common pattern in fact (using a static member as an in-memory cache or the current HttpContext ).