private void AddUser(object sender, DataGridViewCellEventArgs e) { var rows = this.dataGridView1.CurrentRow; if (rows == null) { return; } var user = BusinessUser.GetUserById(new Guid(rows.Cells["UserId"].Value.ToString())); if (_buys == null) { this._sellTickets.AddUser(user); } else { this._buys.AddUser(user); } this.Hide(); }