How to select mult items in listbox from backend code(VB)?

Question

I am using VB. How to select mult items in listbox frombackend code?

Below, I have a listbox where user can select muti items.

<asp:ListBox ID="lb" SelectionMode="multiple" runat="server"  DataValueField="dv">
        <asp:ListItem>red r</asp:ListItem>
        <asp:ListItem>blue b</asp:ListItem>
        <asp:ListItem>green g</asp:ListItem>
</asp:ListBox>

What I have tierd so far:

How can I set so the value of "blue b" and "green g" is already selected? I tried setSelected but this method is not supported

lb.SetSelected(1, True)
lb.SetSelected(2, True)

I also tried this below which kind of works. It does select 1 value but I need to able to select multi values.

lb.Text = "blue b"
lb.Text = "green g"

I tried this also and it doesn't select any values.

lb.Text = "blue b green g"

I wanted to come back here and let you know why .Text was behaving the way it is for you. The Text property lets you get or set the currently selected item. By selected in this case, I'm not referring to it being highlighted. Instead, selected means the item that currently has focus. You can see this when you select an item. When focused it should have a border around it in addition to the highlight. Understanding this then you should understand what your code is doing. — Michael Z.
– Michael Z., Commented May 21, 2016 at 3:48

Michael Z. · Accepted Answer · 2016-05-20 15:44:28Z

1

Try using this loop. You need to change the hard-coded blue b value for a variable. I responded to a similar post that I thought was .Net instead of ASP.net. The SetSelected method is not available in ASP.net.

For Loop:

For i As Integer = 0 To listbox.Items.Count - 1 Step 1
  If listbox.Items(i).Value = "blue b" Then
      listbox.Items(i).Selected = true
  End If
Next

For Each Loop:

For Each item As ListItem In ListBox.Items
    If item.Value = "blue b" Then
        item.Selected = True
    End If
Next

You could also try this without a loop:
I would say this is the preferred method because you can just loop through your list of values you want selected and use this line of code. All you need to change is the string inside FindByValue.

listbox.Items(listbox.Items.IndexOf(listbox.Items.FindByValue("blue b"))).Selected = True

edited May 20, 2016 at 15:44

answered May 20, 2016 at 13:56

Michael Z.

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3 Comments

user1924249 Over a year ago

Thanks! getting an error on ListBoxItem"-- ListBoxItem is not defined

Michael Z. Over a year ago

I'm looking for an IndexOf() method that you could use in place of the loop. There should be an IndexOf() in the Items collection where you can pass in your string and it will find the index of that item.

Michael Z. Over a year ago

I added a way to do this without a loop.

Ed Gibbs · Accepted Answer · 2016-05-20 13:36:27Z

0

This should do the trick:

lb.Items(1).Selected = True
lb.Items(2).Selected = True

And in your postback code, get the user-selected values with lb.GetSelectedIndices.

answered May 20, 2016 at 13:36

Ed Gibbs

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