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>