inserting a single column value using linq to entity

public ActionResult Invite(string txt_inviteemail)
{
     E2EEntities1 entities = new E2EEntities1();
    E2E_Mstuserdetails userdetails = new E2E_Mstuserdetails();

    var validuser = entities.E2E_Mstuserdetails.Select(email => email.email).ToList();
    //string valid = validuser[0].ToString();

    foreach (string vEmail in validuser)
    {
        if (vEmail != txt_inviteemail)
        {
            userdetails.email = txt_inviteemail;
            //entities.E2E_Mstuserdetails.Add(userdetails.email);
           
            entities.E2E_Mstuserdetails.Add(userdetails);
            
            entities.SaveChanges();
        }
    }