gistfile1.txt

using System;
using System.IO;
using System.Linq;
using Tridion.ContentManager.ContentManagement;
using Tridion.ContentManager.Extensibility;
using Tridion.ContentManager.Extensibility.Events;

namespace Tridion.EventSystem
{

    [TcmExtension("ComponentSave")]
    public class ComponentSave : TcmExtension
    {
        public ComponentSave() 
        {
            EventSystem.Subscribe<Component, SaveEventArgs>( ComponentSaveInitiatedHandler, EventPhases.Initiated);
        }

        private void ComponentSaveInitiatedHandler(Component component, SaveEventArgs args, EventPhases phase)
        {
            PreventCircularReferences(component);
        }

        List<string> _metaFieldNames = new List<string>{"mobile", "mobile-alt"};
        /// <summary>
        /// Don't allow a Component to link to itself in the Metadata field
        /// </summary>
        /// <param name="component"></param>
        private void PreventCircularReferences(Component component)
        {
            foreach (string fieldname in _metaFieldNames)
            {
                if ((component.Metadata != null) && (component.Metadata[fieldname] != null) && (component.Metadata[fieldname].Attributes["xlink:href"].Value != ""))
                {
                    string linkedComponentUri = component.Metadata[fieldname].Attributes["xlink:href"].Value;
                    Component linkedComponent = (Component)component.Session.GetObject(linkedComponentUri);

                    if (linkedComponent.Id.ItemId == component.Id.ItemId)
                    {
                        throw new CircularReferenceException("The current Component is linked to itself in the Metadata fields.  This is a problem.  Please remove the Metadata Component Link to this Component. Thank you.");
                    }
                }
            }
        }

        [Serializable]
        public class CircularReferenceException : Exception
        {
            public CircularReferenceException() { }
            public CircularReferenceException(string message) : base(message) { }
            public CircularReferenceException(string message, Exception inner) : base(message, inner) { }
            protected CircularReferenceException(
            System.Runtime.Serialization.SerializationInfo info,
            System.Runtime.Serialization.StreamingContext context)
             : base(info, context) { }
        }
    }
}