C#

private int AddUser(UserEntity User)
{
    int retVal = 0;

    using (var dc = getDataContext())
    {
        var user = (from u in dc.tblUsers
                    where u.CompanyId == User.CompanyId &&
                            u.UserName.Trim().ToLower() == User.UserName.Trim().ToLower()
                    select u).FirstOrDefault();

        if (user == null)
        {
            tblUser newUser = new tblUser
            {
                CompanyId = User.CompanyId,
                RoleId = User.RoleId,
                FirstName = User.FirstName,
                LastName = User.LastName,
                UserName = User.UserName,
                Password = User.Password,
                CanLogIn = User.CanLogIn
            };

            // Wrap this in a try/catch, or handle exceptions in the BLL?
            dc.tblUsers.InsertOnSubmit(newUser);
                    
                    
            retVal = newUser.UserId;
        }
        else
        {
            // If here, the user already exists. Throw an exception here?
        }
    }

    return retVal;
}