如何在C＃中设置组合框的选定值

Question

I have two combo box ( say cbo_zone & cbo_floor ) which are having table as the data source

private void load_cbo_zone() 
    { 
        clz_Common_References ccr = new clz_Common_References ();
        DataTable dt_zone = ccr.get_zone_detail();
        cbo_zone.DataSource = dt_zone;
        cbo_zone.ValueMember = "ID";
        cbo_zone.DisplayMember = "zone";
        cbo_zone.SelectedIndex = -1;
    }

`

    private void load_cbo_floor()
    {
        int ID_zone_ref = Convert.ToInt16(cbo_zone.SelectedValue);
        clz_Common_References ccr = new clz_Common_References();
        DataTable dt_flr = ccr.get_floor_data_fr_Ref_IDZone(ID_zone_ref);
        cbo_floor.DataSource = dt_flr;
        cbo_floor.DisplayMember = "Floor";
        cbo_floor.ValueMember = "ID";
        cbo_floor.SelectedIndex = -1;
    }

` . I wrote the code to update the cbo_floor as following .

private void cbo_zone_SelectionChangeCommitted(object sender, EventArgs e)
    {
        load_cbo_floor();
    }

Now I need to update the cbo_zone & cbo_floor when I click a data row of datagridview .

int ref_area_id, ref_floor_id, ref_zone_id;

        int.TryParse(dt_issued_mat.Rows[0][11].ToString(), out ref_area_id);
        DataTable dt_area_detail = ccr.get_area_data_fr_area_id(ref_area_id);
        int.TryParse(dt_area_detail.Rows[0][2].ToString(), out ref_floor_id);
        DataTable dt_floor_detail = ccr.get_floor_data_fr_floor_id(ref_floor_id);
        int.TryParse(dt_floor_detail.Rows[0][2].ToString(), out ref_zone_id);
        DataTable dt_zone_detail = ccr.get_zone_data_fr_zone_id(ref_zone_id);

after that using

cbo_zone.Text  = dt_zone_detail.Rows[0][1].ToString();
cbo_floor.Text  = dt_floor_detail.Rows[0][1].ToString();

I was able to display the values on the combo boxes but once I tried to get the cbo_floor.SelectedValue code doesn't work .

Then I was able to get the relevant SelectedIndex by using ,

int index = cbo_zone.FindString(dt_zone_detail.Rows[0][1].ToString());
        cbo_zone.SelectedIndex  = index ;

still the combo box shows nothing & "cbo_zone.SelectedValue" doesn't show a value.my target is to get the cbo_floor.SelectedValue . Please help .

Answer 1

Instead of cbo_zone.Text = dt_zone_detail.Rows[0][1].ToString(); cbo_floor.Text = dt_floor_detail.Rows[0][1].ToString(); cbo_zone.Text = dt_zone_detail.Rows[0][1].ToString(); cbo_floor.Text = dt_floor_detail.Rows[0][1].ToString();

Use

cbo_zone.Items.Add( dt_zone_detail.Rows[0][1].ToString());

cbo_floor.Items.Add ( dt_floor_detail.Rows[0][1].ToString());

Answer 2

First working with indexes is not a good idea. You have the value, use them. Using the index will cause you trouble.

cbo_zone.SelectedValue = myValue.ToString();//find the value from your data

Secondly for selecting the floor, you need to fill it with the relevant values first, since it already has the data for the last selection.

  load_cbo_floor();
  cbo_floor.SelectedValue = myValue.ToString();//find the value from your data