SF - HierarchicalTaxonField designer -> Control

*** DESIGNER.ascx ***
<li class="sfFormCtrl">
    <h2>Which video content would you like to display?</h2>
    <sitefinity:HierarchicalTaxonField ID="FilterCategory" runat="server" DisplayMode="Write" Expanded="false" ExpandText="Add Category" ShowDoneSelectingButton="true" AllowMultipleSelection="true" BindOnServer="false" TaxonomyMetafieldName="Category" WebServiceUrl="~/Sitefinity/Services/Taxonomies/HierarchicalTaxon.svc" TaxonomyId="E5CD6D69-1543-427B-AD62-688A99F5E7D4" />
    <div class="sfExample">Select the video category your would like to display.</div>
</li>

*** DESIGNER.cs ***
protected virtual HierarchicalTaxonField FilterCategory
{
    get
    {
        return this.Container.GetControl<HierarchicalTaxonField>("FilterCategory", true);
    }
}

public override System.Collections.Generic.IEnumerable<System.Web.UI.ScriptDescriptor> GetScriptDescriptors()
{
    var scriptDescriptors = new List<ScriptDescriptor>(base.GetScriptDescriptors());
    var descriptor = (ScriptControlDescriptor)scriptDescriptors.Last();

    descriptor.AddComponentProperty("FilterCategory", this.FilterCategory.ClientID);

    return scriptDescriptors;
}

*** DESIGNER.js ***
// Called when the designer window gets opened and here is place to "bind" your designer to the control properties
refreshUI: function () {
    var controlData = this._propertyEditor.get_control(); // JavaScript clone of your control - all the control properties will be properties of the controlData too
    controlData.CategoryIdsStr && this.get_FilterCategory().set_value(controlData.CategoryIdsStr.split(','));
},
// Called when the "save" button is clicked. Here you can transfer the settings from the designer to the control
applyChanges: function () {
    var controlData = this._propertyEditor.get_control();
    controlData.CategoryIdsStr = this.get_FilterCategory().get_value() ? this.get_FilterCategory().get_value().join() : "";
},

*** CONTROL.cs ***
using Telerik.Sitefinity.Data.Linq.Dynamic;

public string CategoryIdsStr { get; set; }
private List<Guid> categoryIds
{
    get
    {
        return CategoryIdsStr.IsNullOrWhitespace() ? new List<Guid>() : CategoryIdsStr.Split(',').Where(o => o.IsGuid()).Select(o => o.ToGuid()).ToList();
    }
}
private string categoryIdFilterClause
{
    get
    {
        var clauses = categoryIds.Select(o => string.Format("Category.Contains(({0}))", o));
        return string.Join(" OR ", clauses);
    }
}

private void PopulateControl()
{
    //Videos with a valid (length check only) Youtube video code
    var videoCollection = SitefinityFunctions.GetDynamicContentItemsAsQueryable("VideoContent.Video").Where(o => o.GetValue<string>("VideoCode").Length == 11);

    if (!categoryIdFilterClause.IsNullOrWhitespace())
    {
        videoCollection = videoCollection.Where(categoryIdFilterClause);
    }

    //Sorted please
    var sortedVideoCollection = videoCollection.ToList().OrderBy(o => o.GetValue<decimal>("SortOrder"));

    if (videoCollection.Any())
    {
        rptVideoSlider.DataSource = sortedVideoCollection;
        rptVideoSlider.ItemDataBound += rptVideoSlider_ItemDataBound;
        rptVideoSlider.DataBind();
    }
    else
    {
        this.Visible = false;
    }
}