I would like to implement a list picker with item grouping in the destination Asp.Net RadListBox.

Unfortunately the Telerik Asp.net RadListBox control does not seem to support item grouping natively. I have seen a forum post from 2019 that suggests adding custom group items https://www.telerik.com/forums/subheadings-in-radlistbox  We could do this but would prefer a more native solution.

Code to replicate the issue

<telerik:RadListBox
    RenderMode="Lightweight"
    runat="server"
    ID="RadListBoxSource"
    AllowTransfer="true"
    TransferToID="RadListBoxDestination"
    ButtonSettings-AreaWidth="35px">
    <EmptyMessageTemplate>
        empty message
    </EmptyMessageTemplate>
</telerik:RadListBox>
<telerik:RadListBox
    RenderMode="Lightweight"
    runat="server"
    ID="RadListBoxDestination"
    ButtonSettings-AreaWidth="35px">
    <EmptyMessageTemplate>
        empty message2
    </EmptyMessageTemplate>
</telerik:RadListBox>

Enabling/Disabling the ListBox on the client is not persisted across PostBacks.

To replicate the issue

ListBox markup

<telerik:RadListBox runat="server" ID="RadListBoxA" CheckBoxes="true" Enabled="false">
    <Items>
        <telerik:RadListBoxItem Text="Item 1" />
        <telerik:RadListBoxItem Text="Item 2" />
        <telerik:RadListBoxItem Text="Item 3" />
        <telerik:RadListBoxItem Text="Item 4" />
    </Items>
</telerik:RadListBox>

<telerik:RadButton runat="server" ID="RadButton1" Text="Toggle State" AutoPostBack="false" OnClientClicked="ToggleListBoxStates" />
<telerik:RadButton runat="server" ID="RadButton2" Text="Postback" AutoPostBack="true" />

OnClientClicked event handler

function ToggleListBoxStates(sender, args) {
    var listBoxA = $find("<%= RadListBoxA.ClientID %>");
    listBoxA.trackChanges();
    listBoxA.set_enabled(!listBoxA.get_enabled());
    listBoxA.commitChanges();
}

Run the example, change the ListBox state and do a PostBack.

Notice, the state changes back.

RadListBox allows to declaratively bind the Text and Value properties of the ListItems, e.g:

<telerik:RadListBox runat="server" DataTextField="Text" DataValueField="Id">

Unfortunately, this is not possible for the ImageUrl property.

My Suggestion: please allow to also bind the ImageUrl declaratively as known from other controls, e.g:

<telerik:RadListBox runat="server" DataTextField="Text" DataValueField="Id"
    DataImageUrlField="..."

// and maybe even like this:

    DataImageUrlFormatString="..." DataImageUrlFields="...">

Replicate by dragging a RadListBox item vertically in the Drag-and-drop demo, on a mobile device.

Hi,

Would love to have feature for reorder animation and drop placeholder when user is reordering the item(s) in the Radlistbox.

A example would be the list in invisionapp.com as attached.

Another example would be like JQUERYUI's sortable plugin. 
URL: https://jqueryui.com/sortable/#placeholder.

Thanks.

The control should provide support for the JAWS screen readers, which will enable it for use by visually impaired users.

More details are available in the following forum thread - https://www.telerik.com/forums/how-is-listbox-usable-for-screen-readers

A workaround is to disable the embedded jQuery and use an older version (for example, 1.11.1 which is the previous version the suite used): https://docs.telerik.com/devtools/aspnet-ajax/controls/scriptmanager/disabling-the-embedded-jquery

Repro steps:

1. put a listbox on the page
2. configure it so it does postbacks (e.g., on selection changed, or any other feature)
3. ivnoke said postback (e.g., select an item)

Expected: the action is carried off

Actual: Firefox throws TypeError: access to strict mode caller function is censored

Sample markup

        <telerik:RadListBox runat="server" ID="rlb1" OnSelectedIndexChanged="rlb1_SelectedIndexChanged" AutoPostBack="true">
            <Items>
                <telerik:RadListBoxItem Text="first" Selected="true" />
                <telerik:RadListBoxItem Text="second" />
            </Items>
        </telerik:RadListBox>

When using:

Value = "(null)"
Text = "(no user)"

as item in the ListBox, the filter must work correctly, and after opening the menu the item should be checked if previously filtered.

Additionally if the item have NULL value instead of "(null)" The visible value must be localized.