正在检索用户电子邮件&；显示Team Foundation Server中的名称

我的目标是在TFS中检索整个用户的整个电子邮件地址。我终于成功地获得了用户的SID列表，但我认为这没关系，因为组中有一些组我检索SID，我不知道如何访问它。这是我代码中的重要部分，希望能在这里得到答案。

  TeamFoundationIdentity[] projectGroups = _ims.ListApplicationGroups(projectUri, ReadIdentityOptions.None);
            Dictionary<IdentityDescriptor, object> descSet = new Dictionary<IdentityDescriptor, object>(IdentityDescriptorComparer.Instance);
            foreach (TeamFoundationIdentity projectGroup in projectGroups)
            {
                descSet[projectGroup.Descriptor] = projectGroup.Descriptor;
            }
            // Expanded membership of project groups
            projectGroups = _ims.ReadIdentities(descSet.Keys.ToArray(), MembershipQuery.Expanded, ReadIdentityOptions.None);
            // Collect all descriptors
            foreach (TeamFoundationIdentity projectGroup in projectGroups)
            {
                foreach (IdentityDescriptor mem in projectGroup.Members)
                {
                    TeamFoundationIdentity[] _identities = _ims.ReadIdentities(new IdentityDescriptor[] {mem}, MembershipQuery.Expanded, ReadIdentityOptions.None);
                   foreach(TeamFoundationIdentity id in _identities)
                   {
                      //the sid
                      Console.WriteLine(id.Descriptor.Identifier);
                   }
                }
            }
        }

IGroupSecurityService gss = (IGroupSecurityService)tfsConnection.GetService(typeof(IGroupSecurityService));
Identity SIDS = gss.ReadIdentity(SearchFactor.AccountName, "Project Collection Valid Users", QueryMembership.Expanded);
Identity[] UserId = gss.ReadIdentities(SearchFactor.Sid, SIDS.Members, QueryMembership.None);
foreach (Identity user in UserId)
{    
 // check if group or user
 if (!user.SecurityGroup)
 {
  Console.Writeln(user.DisplayName +" -> "+ user.Domain + "'" + user.AccountName + "-" + user.MailAddress);
 }
}