Can't set Combobox SelectedItem, Value

Question

In my application I have a customer who can have multiple locations. When you select a customer in my dropdownbox, it will load comboboxes in a flowlayoutpanel with all it's locations.

This is my code for this:

        IEnumerable<locatie> opstapPlaatsen = Database.getOpstapplaatsen(klant.klant_id);

        foreach (locatie opstapplaats in opstapPlaatsen)
        {

            if (opstapPlaatsen.Count() <= 0)
            {

            }
            else
            {
                ComboBox cbbOpstap = new ComboBox();
                cbbOpstap.Width = 200;
                cbbOpstap.Height = 20;

                cbbOpstap.DataSource = Database.getLocaties();
                cbbOpstap.ValueMember = "locatie_id";
                cbbOpstap.SelectedValue = opstapplaats.locatie_id;
                cbbOpstap.SelectedItem = opstapplaats;
                cbbOpstap.DisplayMember = "FullAdress";

                flpOpstapplaats.Controls.Add(cbbOpstap);
            }
        }

My problem is that I can't set the SelectedItem or/and Value. When I look with breakpoints there is a value in opstapplaats.locatie_id (the correct one), but SelectedValue stays null.

I do something alike outside of a loop, and for a combobox not created in code, and it works there.

I have no idea what's causing this? Is this because it's in a foreach, because I used it before out of a foreach and then it worked.

Solution 1

Turns out you have to first add the control to the panel, and then set the ValueMember, DisplayMember...

ComboBox cbbOpstap = new ComboBox();

cbbOpstap.Width = 200;
cbbOpstap.Height = 20;

flpOpstapplaats.Controls.Add(cbbOpstap);

cbbOpstap.ValueMember = "locatie_id";
cbbOpstap.DisplayMember = "FullAdress";
bbOpstap.DataSource = LocatieManagement.getLocaties();  

cbbOpstap.SelectedValue = opstapplaats.locatie_id;
cbbOpstap.SelectedItem = opstapplaats;

Then it works, I hope this can help somebody!

Solution 2

When you set the Valuemember and displayMember, please use SelectedIndex to select an item.

cbbOpstap.DataSource = Database.getLocaties();
cbbOpstap.ValueMember = "locatie_id";
cbbOpstap.DisplayMember = "FullAdress";
cbbOpstap.SelectedIndex = cbbOpstap.Items.IndexOf(opstapplaats.locatie_id);

Comments

[Schoof]

The code works, but it also doesn't change the SelectedIndex, it's still always at the default (-1). I have made a screenshot of the problem, to clarify.

[PraveenVenu]

Are you sure that there is an item with the value opstapplaats.locatie_id in the dropdown?

[V4Vendetta]

@ThomasSchoof Just check if the value you are passing is in the same case as in the Items list.

[Schoof]

There appear to be no items in the combobox, but the datasource is filled! Here you can see the filled datasource, I'm not sure what's causing this?

[PraveenVenu]

is it a webapplication or windows application?

[Schoof]

I do exactly the same thing out of the foreach (to just get the adress) and there it just works. i.imgur.com/5g4RR.png

[steven2308]

By the way it has to be in that same order, i.e. If first you set the ValueMember, DisplayMember and DataSource and then you add the control to the form (which is what I was trying to do since my combo is filled dynamically from different tables and it may not find the source) you won't be able to set the SelectedValue.