I would like to add dynamically a tab ...

I assume that you would like to add WebTab item dynamically from client-side. The snippet code below shows a JavaScript function that is used to add WebTab item from client-side.

Please let me know if this is not what you're after to.

<script type="text/javascript">
    <!--
    var tabNewIndex = 1;

    function AddNewTab() {
        var tab = ISGetObject("WebTab1");
        var newItem = tab.AddNewTabItem("Untitled" + tabNewIndex, "Untitled " + tabNewIndex, null);

        newItem.SetActive(); // set the newly created tab item as active.
        tabNewIndex++;
    }
    //-->
</script>

... I would like to load an ascx (or aspx) on tab...

By default, the WebTab will operate in "UseInlineContent" mode when a new instance is dropped to designer surface. UseInlineContent is the most suitable when the contents inside each tab page are relatively small. You can also determine the "content load" by inspecting the performance during page load as well as the size of the output. UseInlineContent mode utilized .NET Framework's Templating archictecture and therefore all contents are loaded at once in first load (although the inactive pages are set to hidden).

In most cases where you want to develop a more reusable form, you should use UseIFrame for the content mode. When using IFrame mode, you would need to specify the ContentURL which page you want to load for the designated Tab item.

The ContentURL accepts three formats of URL:

• .NET specific application relative URL. This format starts with "~" character, for instance, "~/FolderA/Page1.aspx".
• Absolute URL. This format starts with "/" character, for instance, "/SharedModule/Page1.aspx".
• Relative URL. This format usually starts with "." character or no special characters (which assume the page can be found in the current folder's context).

You can configure different ContentMode for each TabItem. To apply all TabItem to use a specific ContentMode, configure the ContentMode in WebTab control level and leave TabItem's ContentMode to Default.

For more detail information, please kindly check the WebDesktop documention, specifically in WebTab section.

Glad to hear the good news.

Should you need further assistance or run into any problems regarding our controls, feel free to post it into our community. We would be happy to assist you again.