<%@ Register Assembly="AsyncControls" Namespace="DelvingWare.AsyncControls" TagPrefix="dw" %>

<dw:AsyncListBox runat="server" ID="drpMain" 
Rows="10" 
OnSelectedIndexChanged="drpMain_IndexChanged">
    <AsyncListItem Value="one" Text="List Item One" />
    <AsyncListItem Value="two" Selected="true" Text="List Item Two" />
    <AsyncListItem Value="three" Text="List Item Three" />
</dw:AsyncListBox>

<dw:AsyncLabel runat="server" ID="lblMain">Change the selected item.</dw:AsyncLabel>

<dw:AsyncButton runat="server" ID="btAdd" 
OnClick="btAdd_Click"
CssClass="greyButton">Add Item</dw:AsyncButton>

<dw:AsyncButton runat="server" ID="btRemove" 
OnClick="btRemove_Click"
CssClass="greyButton">Remove Selected Item</dw:AsyncButton>

using System;
using DelvingWare.AsyncControls;
...
protected void Page_Load( object sender, EventArgs e )
{
    if ( !IsPostBack )
    {
        // add 5 more items during page load
        for ( int i = 0, num = 0 ; i < 5 ; ++i )
        {
            num = drpMain.Items.Count+1;

            // add the list item
            drpMain.Items.Add("List Item "+ num, num.ToString());                
        }
    } 
}

protected void drpMain_IndexChanged( object sender, AsyncEventArgs ae )
{
    // update the label to show all selections
    foreach ( AsyncListItem item in drpMain.SelectedItems )
    {
        lblMain.Text += "Selected Text: "+ item.Text +
            " (Value: "+ item.Value +")<br/>";
    } // end FOREACH

    // adjust button text based on selection count
    if ( drpMain.SelectedItems.Length > 1 )
        btRemove.Text = "Remove Selected Items!";
}

protected void btAdd_Click( object sender, AsyncEventArgs ae )
{
    if ( drpMain.Items.Count == 20 )
    {
        AsyncPage.Alert("This demo only allows 20 items.");
        return;
    } // end iF

    int itemCount = drpMain.Items.Count+1;

    drpMain.ClearSelection();
    drpMain.Items.Add("List Item "+ itemCount, itemCount.ToString(), true);
    
    lblMain.Text = "Selected Text: "+ drpMain.LastItem.Text +
        " (Value: "+ drpMain.LastItem.Value +")";
}

protected void btRemove_Click( object sender, AsyncEventArgs ae )
{
    if ( drpMain.Items.Count == 0 )
    {
        AsyncPage.Alert("No items to remove.");
        return;
    } 

    if ( drpMain.SelectedIndex > -1 )
    {
        foreach( AsyncListItem item in drpMain.SelectedItems )
        {
            drpMain.Items.Remove(item);
        } // end FOREACH

        drpMain.ClearSelection();
        lblMain.Text = "No items selected.";
    } 
    else
        AsyncPage.Alert("Please select an item to remove.");
}

Imports System
Imports DelvingWare.AsyncControls
...

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    If Not IsPostBack Then
        ' add 5 more items during page load
        Dim num As Integer = 0
        Do While (i < 5)
            
        Loop
        Dim i As Integer = 0
        i
        num = (drpMain.Items.Count + 1)
        ' add the list item
        drpMain.Items.Add(("List Item " + num), num.ToString)
    End If
End Sub

Protected Sub drpMain_IndexChanged(ByVal sender As Object, ByVal ae As AsyncEventArgs)
    ' update the label to show all selections
    For Each item As AsyncListItem In drpMain.SelectedItems
        lblMain.Text = (lblMain.Text + ("Selected Text: "  _
                    + (item.Text + (" (Value: "  _
                    + (item.Value + ")<br/>")))))
    Next
    ' end FOREACH
    ' adjust button text based on selection count
    If (drpMain.SelectedItems.Length > 1) Then
        btRemove.Text = "Remove Selected Items!"
    End If
End Sub

Protected Sub btAdd_Click(ByVal sender As Object, ByVal ae As AsyncEventArgs)
    If (drpMain.Items.Count = 20) Then
        AsyncPage.Alert("This demo only allows 20 items.")
        Return
    End If
    ' end iF
    Dim itemCount As Integer = (drpMain.Items.Count + 1)
    drpMain.ClearSelection
    drpMain.Items.Add(("List Item " + itemCount), itemCount.ToString, true)
    lblMain.Text = ("Selected Text: "  _
                + (drpMain.LastItem.Text + (" (Value: "  _
                + (drpMain.LastItem.Value + ")"))))
End Sub

Protected Sub btRemove_Click(ByVal sender As Object, ByVal ae As AsyncEventArgs)
    If (drpMain.Items.Count = 0) Then
        AsyncPage.Alert("No items to remove.")
        Return
    End If
    If (drpMain.SelectedIndex > -1) Then
        For Each item As AsyncListItem In drpMain.SelectedItems
            drpMain.Items.Remove(item)
        Next
        ' end FOREACH
        drpMain.ClearSelection
        lblMain.Text = "No items selected."
    Else
        AsyncPage.Alert("Please select an item to remove.")
    End If
End Sub