Microsoft CRM插件无限循环

恐怕我还有另一个MS CRM问题.我已经在更新联系人记录时执行了以下代码，但是它给我一个错误，指出该作业被取消，因为它包含无限循环.谁能告诉我为什么会这样吗?

Another MS CRM question from me, I'm afraid. I've got the following code being executed on the update of a contact record but it gives me an error saying the job was cancelled because it includes an infinite loop. Can anyone tell me why this is happening, please?

// <copyright file="PostContactUpdate.cs" company="">
// Copyright (c) 2013 All Rights Reserved
// </copyright>
// <author></author>
// <date>8/7/2013 2:04:26 PM</date>
// <summary>Implements the PostContactUpdate Plugin.</summary>
// <auto-generated>
//     This code was generated by a tool.
//     Runtime Version:4.0.30319.1
// </auto-generated>
namespace Plugins3Test
{
    using System;
    using System.ServiceModel;
    using Microsoft.Xrm.Sdk;
    using Microsoft.Xrm.Sdk.Query;

    /// <summary>
    /// PostContactUpdate Plugin.
    /// Fires when the following attributes are updated:
    /// All Attributes
    /// </summary>    
    public class PostContactUpdate: Plugin
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="PostContactUpdate"/> class.
        /// </summary>
        public PostContactUpdate()
            : base(typeof(PostContactUpdate))
        {
            base.RegisteredEvents.Add(new Tuple<int, string, string, Action<LocalPluginContext>>(40, "Update", "contact", new Action<LocalPluginContext>(ExecutePostContactUpdate)));

            // Note : you can register for more events here if this plugin is not specific to an individual entity and message combination.
            // You may also need to update your RegisterFile.crmregister plug-in registration file to reflect any change.
        }

        /// <summary>
        /// Executes the plug-in.
        /// </summary>
        /// <param name="localContext">The <see cref="LocalPluginContext"/> which contains the
        /// <see cref="IPluginExecutionContext"/>,
        /// <see cref="IOrganizationService"/>
        /// and <see cref="ITracingService"/>
        /// </param>
        /// <remarks>
        /// For improved performance, Microsoft Dynamics CRM caches plug-in instances.
        /// The plug-in's Execute method should be written to be stateless as the constructor
        /// is not called for every invocation of the plug-in. Also, multiple system threads
        /// could execute the plug-in at the same time. All per invocation state information
        /// is stored in the context. This means that you should not use global variables in plug-ins.
        /// </remarks>
        protected void ExecutePostContactUpdate(LocalPluginContext localContext)
        {
            if (localContext == null)
            {
                throw new ArgumentNullException("localContext");
            }

            // TODO: Implement your custom Plug-in business logic.

            // Obtain the execution context from the service provider.
            IPluginExecutionContext context = localContext.PluginExecutionContext;
            IOrganizationService service = localContext.OrganizationService;
            IServiceProvider serviceProvider = localContext.ServiceProvider;
            ITracingService tracingService = localContext.TracingService;


            // Obtain the target entity from the input parmameters.
            //Entity contextEntity = (Entity)context.InputParameters["Target"];




                Entity targetEntity = null;
                targetEntity = (Entity)context.InputParameters["Target"];
                Guid cid = targetEntity.Id;
                ColumnSet cols = new ColumnSet("jobtitle");

                Entity contact = service.Retrieve("contact", cid, cols);
                contact.Attributes["jobtitle"] = "Sometitle";
                service.Update(contact);





        }
    }
}