EF Inserts already existing item
protected void Application_BeginRequest(Object sender, EventArgs e)
{
    //-- Create an instance of EntityContext
    HttpContext.Current.Items[Constants.ENTITYCONTEXT] = new EntityContext();
}
protected void Application_EndRequest(Object sender, EventArgs e)
{
    //-- Clean up the entitycontext
    var entityContext = HttpContext.Current.Items[Constants.ENTITYCONTEXT] as EntityContext;
    if (entityContext != null)
        entityContext.Dispose();
}

//-- EntityContext
private EntityContext CurrentContext
{
    get { return HttpContext.Current.Items[Constants.ENTITYCONTEXT] as EntityContext; }
}

private Domain.Model.Club LoadClubByIdentifier(Guid identifier)
{
    return this.CurrentContext.Clubs.SingleOrDefault(c => c.Identifier == identifier);
}

Domain.Model.User user = Mapper.Map<Web.Content.Code.Models.User.CreatePlayer, Domain.Model.User>(model);
user.Identifier = new Guid().NewSequentialGuid();

//-- Get current club
user.Clubs.Add(base.CurrentClub);

//-- Get all teams and add them to user
foreach (string teamIdentifier in model.Team)
{
    Domain.Model.Team team = new Domain.Services.TeamServices().LoadByIdentifier(
        Domain.Helper.CryptationHelper.DecryptIdentifier(teamIdentifier));

    user.Teams.Add(new TeamUser() { Team = team, User = user, UserTeamRelation = UserTeamRelationEnum.Player });
}

//-- Create this user
new Domain.Services.UserServices().CreatePlayer(user);

public void CreatePlayer(Domain.Model.User user)
{
    Password password = Password.GenerateRandomPassword();
    user.Password = password;

    //-- Save the user to storage
    _userRepository.SaveUser(user);
}

//-- Methods
private void SaveUser(Domain.Model.User user)
{
    this.CurrentContext.Users.Add(user);
    this.CurrentContext.SaveChanges();
}