private void bt_Tim_Click(object sender, EventArgs e) { if (tb_Loai.Text != "") { lv_dsketqua.Items.Clear(); client = new ServiceReference1.Service1Client(); client.TimkhonggianCompleted += new EventHandler<ServiceReference1.TimkhonggianCompletedEventArgs>(TimkhonggianCallBack); client.TimkhonggianAsync(tb_Loai.Text); } else { lv_dsketqua.Items.Clear(); client = new ServiceReference1.Service1Client(); client.LoadNHCFCompleted += new EventHandler<ServiceReference1.LoadNHCFCompletedEventArgs>(LoadNHCFCallBack); client.LoadNHCFAsync(); } }