Code

void dockControl1_ItemLoading(object sender, ItemEventArgs e)
{
    if (e.Item.Content == null)
    {
        if (e.Item.Id == "TabbedDocument")
            e.Item.Content = GetContent("Tabbed Document");
        // Rest of the items omitted for clarity
    }
}

private Control GetContent(string contentType)
{
    Control control = null;

    // ...

    if (contentType == "Tabbed Document")
    {
        Label label = new Label();
        label.Padding = new Padding(10);
        label.BorderStyle = BorderStyle.None;
        label.Margin = new Padding(0);
        label.Text = "...";
        label.BackColor = Color.White;
        control = label;
    }

    // ...

    return control;
}