ComponentArray.cs

using System;
using System.Linq;
using Tridion.ContentManager.ContentManagement.Fields;
using Tridion.ContentManager.Templating;
using Tridion.ContentManager.Templating.Assembly;
using comm = Tridion.ContentManager.CommunicationManagement;

namespace Tridion.Training.Assemblies
{
    [TcmTemplateTitle("Component Array")]
    public class ComponentArray : ITemplate
    {
        public void Transform(Engine engine, Package package)
        {
            // Get the page object from the package
            Item pageItem = package.GetByType(ContentType.Page);

            // Get the content of the page using  the page's TCMURI
            comm.Page page = engine.GetObject(pageItem.GetAsSource().GetValue("ID")) as  
               comm.Page;
            // Get items from  parameters attached to the TBB            
            string m_ItemName = package.GetValue("itemName");
            // Check if parameters are enmpty
            if (String.IsNullOrEmpty(m_ItemName))
            {
                m_ItemName = "Components";
            }
            // check if page is not empty
            if (page != null)
            {
                string fieldName = "heading";
                var sortedList = 
                    from cp in page.ComponentPresentations
                    let componentFields = new ItemFields(cp.Component.Content, cp.Component.Schema)
                    where componentFields.Contains(fieldName)
                    let textField = componentFields[fieldName] as TextField
                    where null != textField.Value
                    orderby textField.Value
                    select new ComponentPresentation(cp.Component.Id, cp.ComponentTemplate.Id);

                var m_cpList = new ComponentPresentationList();
                m_cpList.AddRange(sortedList);
                
                // push component array into the package
                package.PushItem(m_ItemName, 
                   package.CreateStringItem(ContentType.ComponentArray, m_cpList.ToXml()));
            }
        }
    }
}