How to deselect item on single select listbox?

Discussion in 'ASP .Net Web Controls' started by rpress, Jan 3, 2006.

  1. rpress

    rpress Guest

    In a multi-select listbox one may deselect items, but this does not
    work in a single select listbox. Has anyone come across a way to do
    this? (deselect so that no items are selected)

    rpress, Jan 3, 2006
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  2. 1- Add a HtMLinputButton in the markup
    <input type="button" onclick="ClearList();" value="Clear Selections">

    and add a corresponding javascript:

    <script language="javascript">
    function ClearList()
    var list = document.getElementById("ListBox1");
    if (list) list.selectedIndex =-1;

    2- Add a Button server control:
    <asp:Button ID="btnDeselect" Runat="server" Text="De-Select"></asp:Button>

    and in the codebehind:

    Private Sub btnDeselect_Click(ByVal sender As System.Object, ByVal e As
    System.EventArgs) Handles btnDeselect.Click
    End Sub

    3- You can insert a list item with a blank value for the user to click if
    you wish them to deselect a previously selected item, e.g.

    Dim li As New ListItem("No Selection", "")
    listbox1.Items.Insert(0, li)
    Phillip Williams, Jan 3, 2006
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  3. rpress

    rpress Guest

    Thanks for the input - I was hoping for a way to deselect simply by
    clicking on the selected item.
    rpress, Jan 3, 2006
  4. Unfortunately the default behavior of the ListBox does not allow for
    deselecting a selected item by clicking on it. You can try handling the
    onclick event to the ListBox (client-side):

    <asp:ListBox ID="ListBox1" Runat="server" onclick="toggle();">
    <%-- here are the list items --%>

    and in the Javascript

    function toggle()
    var list = window.event.srcElement;
    if (list)
    if (list.selectedIndex == prevIndex) list.selectedIndex=-1;
    prevIndex = list.selectedIndex;

    This should produce the effect that you were hoping for; namely "to deselect
    simply by clicking on the selected item."
    Phillip Williams, Jan 3, 2006
  5. rpress

    rpress Guest

    Thanks, Phillip - I will give it a try!
    rpress, Jan 3, 2006
  6. rpress

    rpress Guest

    Thanks again - I decided to use the following code on the mousedown
    event to give the effect that a right mouse click clears the listbox.

    function toggle()// toggle clears single select listbox on mouse down
    var list = window.event.srcElement;

    works for me. ;>)
    rpress, Jan 9, 2006
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