Get active directory group membership

[jimbennett57]

Due to a *quirk* in our domain forest, I need to change how I'm getting a logged on user's group membership. When a user authenticates into this application I need to see if they belong to one of 4 groups. In our test environment I was using:

ArrayList groups = new ArrayList();
            foreach (System.Security.Principal.IdentityReference group in
            System.Web.HttpContext.Current.Request.LogonUserIdentity.Groups)
            {
                groups.Add(group.Translate(typeof(System.Security.Principal.NTAccount)).ToString());
            }
            return groups;

Which works perfectly. However I need to modify my approach to query a specific A/D server, and have not been able to figure out how to do this. Does anyone know how I can take the functionality in the code above, and reference a specific domain controller (i.e. LDAP://{domaincontrollername/DC={domain},DC={com} ... etc) to pull a users group membership?

Thanks!