Multi-Root TreeList

MultiRootTreeList.cs

using System;
using System.Linq;
using Sitecore.Diagnostics;
using Sitecore.Globalization;
using Sitecore.Shell.Applications.ContentEditor;
using Sitecore.Text;
using Sitecore.Web;
using Sitecore.Web.UI.HtmlControls;
using Sitecore.Web.UI.WebControls;

namespace Kamsar.FieldTypes
{
	/// <summary>
	/// This field type is like a tree list, but you can specify more than one root item to select from (for example, videos or photos)
	/// The data source roots are specified using pipe delimiting just like regular Sitecore Query language
	/// </summary>
	public class MultiRootTreeList : TreeList
	{
		protected override void OnLoad(EventArgs args)
		{
			Assert.ArgumentNotNull(args, "args");
			base.OnLoad(args);

			if (!Sitecore.Context.ClientPage.IsEvent)
			{
				// find the existing TreeviewEx that the base OnLoad added, get a ref to its parent, and remove it from controls
				var existingTreeView = (TreeviewEx)WebUtil.FindControlOfType(this, typeof(TreeviewEx));
				var treeviewParent = existingTreeView.Parent;

				existingTreeView.Parent.Controls.Clear(); // remove stock treeviewex, we replace with multiroot

				// find the existing DataContext that the base OnLoad added, get a ref to its parent, and remove it from controls
				var dataContext = (DataContext)WebUtil.FindControlOfType(this, typeof(DataContext));
				var dataContextParent = dataContext.Parent;

				dataContextParent.Controls.Remove(dataContext); // remove stock datacontext, we parse our own

				// create our MultiRootTreeview to replace the TreeviewEx
				var impostor = new Sitecore.Web.UI.WebControls.MultiRootTreeview();
				impostor.ID = existingTreeView.ID;
				impostor.DblClick = existingTreeView.DblClick;
				impostor.Enabled = existingTreeView.Enabled;
				impostor.DisplayFieldName = existingTreeView.DisplayFieldName;

				// parse the data source and create appropriate data contexts out of it
				var dataContexts = ParseDataContexts(dataContext);

				impostor.DataContext = string.Join("|", dataContexts.Select(x => x.ID));
				foreach(var context in dataContexts) dataContextParent.Controls.Add(context);

				// inject our replaced control where the TreeviewEx originally was
				treeviewParent.Controls.Add(impostor);
			}
		}

		/// <summary>
		/// Parses multiple source roots into discrete data context controls (e.g. 'dataSource=/sitecore/content|/sitecore/media library')
		/// </summary>
		/// <param name="originalDataContext">The original data context the base control generated. We reuse some of its property values.</param>
		/// <returns></returns>
		protected virtual DataContext[] ParseDataContexts(DataContext originalDataContext)
		{
			return new ListString(DataSource).Select(x => CreateDataContext(originalDataContext, x)).ToArray();
		}

		/// <summary>
		/// Creates a DataContext control for a given Sitecore path data source
		/// </summary>
		protected virtual DataContext CreateDataContext(DataContext baseDataContext, string dataSource)
		{
			DataContext dataContext = new DataContext();
			dataContext.ID = GetUniqueID("D");
			dataContext.Filter = baseDataContext.Filter;
			dataContext.DataViewName = "Master";
			if (!string.IsNullOrEmpty(DatabaseName))
			{
				dataContext.Parameters = "databasename=" + DatabaseName;
			}
			dataContext.Root = dataSource;
			dataContext.Language = Language.Parse(ItemLanguage);

			return dataContext;
		}
	}
}

So useful thanks! 👯