protected void btnInterested_Click(object sender, EventArgs e) { if (!Page.User.Identity.IsAuthenticated) { Response.Redirect("./login.aspx"); } WebshopDataContext dc = new WebshopDataContext(); aspnet_User user = (from ev in dc.aspnet_Users where ev.UserName.Equals(Page.User.Identity.Name) select ev).FirstOrDefault(); ListsOfParticipant lists = (from ev in dc.ListsOfParticipants where ev.EventID == m_eventID && ev.UserID == user.UserId select ev).FirstOrDefault(); if (lists == null) { ListsOfParticipant newLists = new ListsOfParticipant { UserID = user.UserId, EventID = m_eventID, Interested = true }; dc.ListsOfParticipants.InsertOnSubmit(newLists); dc.SubmitChanges(); dc.Dispose(); } else if (lists.Interested == false) { //ListsOfParticipant newLists = new ListsOfParticipant //{ // lists.Interested = true //}; lists.Interested = true; dc.ListsOfParticipants.Attach(lists, true); dc.SubmitChanges(); dc.Dispose(); } }