Question

All I wish to do is simply click a button and the text in a textbox is automatically added as an item in the listbox. Shouldn’t this be straight forward? Whilst debugging, the item is added and I can see the text by watching ListBox1.Items[0], but nothing is displayed in the web page. I had the same problem which i did not solve, in a console application! Can some one please guide me to what I am doing wrong?

protected void Button1_Click(object sender, EventArgs e)
    {
        ListBox1.Items.Add(new ListItem(TextBox1.Text));
    }

Many thanks

Edit:

In a past project, I used the DataSource property, which worked perfectly. I have never yet managed to use the add Items! May be there is some sort of refresh or update?

Page code:

<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>

<asp:ListBox ID="ListBox1" runat="server" Height="150px" Width="295px"></asp:ListBox>

<asp:UpdatePanel ID="updatePanel1" runat="server">
    <ContentTemplate>
        <asp:Button ID="Button1" runat="server" Text="Submit" OnClick="Button1_Click" />
        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    </ContentTemplate>
</asp:UpdatePanel>

Answer 1

Looks like your listbox is outside of the update panel. Pop it inside the update panel:

<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
    <asp:DropDownList ID="DropDownList1" runat="server">
    </asp:DropDownList>
<asp:Button ID="Button1" runat="server" Text="Button" onclick="AddItem" />
</ContentTemplate>
</asp:UpdatePanel>