Really Slow WindowsTokenRoleProvider - asp.net

Question

In an MVC5 application I am using Windows Authentication and wanted to use our Active Directory Groups as roles as this is strictly and intranet application. I am using the WindowsTokenRoleProvider as so:
<roleManager defaultProvider="WindowsProvider" enabled="true" cacheRolesInCookie="false">
<providers>
<add name="WindowsProvider" type="System.Web.Security.WindowsTokenRoleProvider" applicationName="/" />
</providers>
</roleManager>
I have tried a few other variations of that config including using the cookie cache, but the end result is that it takes ~20 seconds per group check. I check role like this:
User.IsInRole(#"Domain\UserName")
Is there something I have completely missed in setting this up? I can't believe it would be normal for authentication to take 20 seconds per check. The user I am checking is in ~50 groups, but I didn't think that would be enough to slow it down so much.

Answer 1

So best solution at this point seems to be this stackoverflow question
I will probably play around with how the roles get checked/added to see if I can pinpoint the issue, but I wouldn't expect this slowness from only being in 50 groups.
UPDATE:
So while actually enumerating my groups I found my user was in over 400 groups which might explain why it took so long. I still don't under stand why the IsInRole method on user would call GetRolesForUser instead of just calling IsUserInRole directly, but this makes things exponentially faster
UPDATE 2:
Old answer was deleted so here is my class:
public class CustomWindowsTokenRoleProvider : WindowsTokenRoleProvider
{
public override string[] GetRolesForUser(string username)
{
List roles = null;
string key = String.Concat(username, ":", base.ApplicationName);
Cache cache = HttpContext.Current.Cache;
if (cache[key] != null)
{
roles = new List(cache[key] as string[]);
}
if (roles == null)
{
roles = new List();
// AppSettings.APPLICATION_GROUPS is an IEnumerable that returns just the groups that my application is interested in checking against
foreach (string role in AppSettings.APPLICATION_GROUPS)
{
if (base.IsUserInRole(username, role));
{
roles.Add(role);
}
}
cache.Insert(key, roles.ToArray(), null, DateTime.Now.AddHours(1), Cache.NoSlidingExpiration);
}
return roles.ToArray();
}
}