SliverLight Web part

做了一个简单的SilverLight WebPart，但第一次做起来并不轻松，除了各种各样的Issue，譬如OnRequestSucceeded没有被触发是因为没有注册OnRequestFailed而执行Fail的原因，但是在OnRequestFailed里面的代码(简单的弹出消息)失败的原因应该与线程有关，总结了各种经验：

第一，当我们使用context.ExecuteQueryAsync(new ClientRequestSucceededEventHandler(OnRequestSucceeded), new ClientRequestFailedEventHandler(OnRequestFailed));来注册事件的时候，不要在OnRequestSucceeded或者OnRequestFailed事件里直接写代码，这个会报线程冲突的错误。应该使用代理。

Dispatcher.BeginInvoke(delegate()
{
      MessageBox.Show("inside OnRequestSucceeded Method" + args.StackTrace.ToString() + args.ErrorDetails);
});

第二个，context的参数指定一定要使用ApplicationContext.Current.Url，否则在运行的时候会报Security的错误（太搞了，我直接使用ClientContext(“http://localhost”)一直报这个错误，SharePoint的设计也太次了，难道是因为不确认是否在本站运行？有些网站里面提到要部署ClientAccessPolicy.xml在IIS根站点目录下，至少对SilverLight WebPart是没有意义的。）

ClientContext context = new ClientContext(ApplicationContext.Current.Url);

第三个，总结学到的SilverLight里两种异步执行的方式

1)clientContext.ExecuteQueryAsync(onQuerySucceeded, onQueryFailed)，注册成功执行后的时间以及失败后的事件

2)通过多线程调用System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(ThreadCallback), context);

一个小技巧点：

Silverlight重新部署后不需要重启IIS或者重置Application Pool，删除IE的客户端缓存就可以。

源码：

public partial class MainPage : UserControl
    {
        public class Project
        {
            public string Title
            {
                get;
                set;
            }

            public DateTime DueDate
            {
                get;
                set;
            }

            public string Description
            {
                get;
                set;
            }
        }
        private ListItemCollection _projects;

        public MainPage()
        {
            InitializeComponent();
            ClientContext context = new ClientContext(ApplicationContext.Current.Url); 
            //System.Threading.SynchronizationContext thread = System.Threading.SynchronizationContext.Current; if (thread == null)
                //thread = new System.Threading.SynchronizationContext();
            //ClientContext context = new ClientContext("http://localhost");
            //context.AuthenticationMode = Microsoft.SharePoint.Client.ClientAuthenticationMode.Default;
            context.Load(context.Web);
            
            List Projects = context.Web.Lists.GetByTitle("Tasks");
            context.Load(Projects);

            CamlQuery query = new Microsoft.SharePoint.Client.CamlQuery();
            string camlQueryXml = "<View><Query><Where><Gt>" +
                "<FieldRef Name='DueDate' />" +
                "<Value Type='DateTime'>2008-01-1T00:00:00Z</Value>" +
                "</Gt></Where></Query><ViewFields>" +
                "<FieldRef Name=\"Title\" /><FieldRef Name=\"Body\" />" +
                "<FieldRef Name=\"DueDate\" />" +
                "</ViewFields></View>";

            query.ViewXml = camlQueryXml;
            _projects = Projects.GetItems(query);
            context.Load(_projects);
            //MessageBox.Show("Test!");
            //context.ExecuteQuery();
            //System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(ThreadCallback), context);
            context.ExecuteQueryAsync(new ClientRequestSucceededEventHandler(OnRequestSucceeded), new ClientRequestFailedEventHandler(OnRequestFailed));
            
        }

        /*private void ThreadCallback(object s)
        {
           // var context = (ClientContext)s;
           // context.ExecuteQuery();
           this.Dispatcher.BeginInvoke(BindData);
        }*/

        private void OnRequestFailed(Object sender, ClientRequestFailedEventArgs args)
        {
            // this is not called on the UI thread 
            //MessageBox.Show("inside OnRequestFailed Method");
            this.Dispatcher.BeginInvoke(delegate()
            {
                MessageBox.Show("inside OnRequestSucceeded Method" + args.StackTrace.ToString() + args.ErrorDetails);
            });
        }

       

        private void OnRequestSucceeded(Object sender, ClientRequestSucceededEventArgs args) 
        { 
            // this is not called on the UI thread 
            //MessageBox.Show("inside OnRequestSucceeded Method");
            this.Dispatcher.BeginInvoke(BindData); 
        }

        private void Failed(ClientRequestFailedEventArgs args)
        {
            MessageBox.Show("inside OnRequestFailed Method" + args);
        }
        
        private void BindData() 
        { 
            List<Project> projects = new List<Project>();
           foreach (ListItem li in _projects) 
            { 
                projects.Add(new Project() 
                { 
                    Title = li["Title"].ToString(), 
                    DueDate = Convert.ToDateTime(li["DueDate"].ToString()), 
                    Description = li["Body"].ToString() 
                }); 
            }
            dataGrid1.ItemsSource = projects; 
        }
    }