实例介绍
【实例简介】
【实例截图】
【实例截图】
【核心代码】
using System; using System.Data; using System.Data.SqlClient; using System.Security.Principal; using System.Threading; using System.Net; using System.Diagnostics; using System.Collections; using System.ComponentModel; using System.Web; using System.Web.Mail; using System.Web.Caching; using System.Web.SessionState; using System.IO; using System.Messaging; namespace TestCacheTimeout { /// <summary> /// Summary description for Global. /// </summary> public class Global : System.Web.HttpApplication { private const string DummyPageUrl = "http://localhost/TestCacheTimeout/WebForm1.aspx"; private const string CONNECTION_STRING = "Data Source=(local);Initial Catalog=tempdb;Integrated Security=SSPI;"; private const string LOG_FILE = @"c:\temp\Cachecallback.txt"; private const string MSMQ_NAME = ".\\private$\\ASPNETService"; private const string DummyCacheItemKey = "GagaGuguGigi"; public static ArrayList _JobQueue = new ArrayList(); /// <summary> /// Required designer variable. /// </summary> private System.ComponentModel.IContainer components = null; public Global() { InitializeComponent(); } protected void Application_Start(Object sender, EventArgs e) { RegisterCacheEntry(); } /// <summary> /// Register a cache entry which expires in 1 minute and gives us a callback. /// </summary> /// <returns></returns> private void RegisterCacheEntry() { // Prevent duplicate key addition if( null != HttpContext.Current.Cache[ DummyCacheItemKey ] ) return; HttpContext.Current.Cache.Add( DummyCacheItemKey, "Test", null, DateTime.MaxValue, TimeSpan.FromMinutes(1), CacheItemPriority.NotRemovable, new CacheItemRemovedCallback( CacheItemRemovedCallback ) ); } /// <summary> /// Callback method which gets invoked whenever the cache entry expires. /// We can do our "service" works here. /// </summary> /// <param name="key"></param> /// <param name="value"></param> /// <param name="reason"></param> public void CacheItemRemovedCallback( string key, object value, CacheItemRemovedReason reason ) { Debug.WriteLine("Cache item callback: " DateTime.Now.ToString() ); // Do the service works DoWork(); // We need to register another cache item which will expire again in one // minute. However, as this callback occurs without any HttpContext, we do not // have access to HttpContext and thus cannot access the Cache object. The // only way we can access HttpContext is when a request is being processed which // means a webpage is hit. So, we need to simulate a web page hit and then // add the cache item. HitPage(); } /// <summary> /// Hits a local webpage in order to add another expiring item in cache /// </summary> private void HitPage() { WebClient client = new WebClient(); client.DownloadData(DummyPageUrl); } /// <summary> /// Asynchronously do the 'service' works /// </summary> private void DoWork() { Debug.WriteLine("Begin DoWork..."); Debug.WriteLine("Running as: " WindowsIdentity.GetCurrent().Name ); DoSomeFileWritingStuff(); DoSomeDatabaseOperation(); DoSomeEmailSendStuff(); DoSomeMSMQStuff(); ExecuteQueuedJobs(); Debug.WriteLine("End DoWork..."); } /// <summary> /// Execute jobs that are queued for execution at a specific time /// </summary> private void ExecuteQueuedJobs() { ArrayList jobs = new ArrayList(); // Collect which jobs are overdue foreach( Job job in _JobQueue ) { if( job.ExecutionTime <= DateTime.Now ) jobs.Add( job ); } // Eecute the jobs that are overdue foreach( Job job in jobs ) { lock( _JobQueue ) { _JobQueue.Remove( job ); } job.Execute(); } } /// <summary> /// Test file write. Make sure the path allows ASPNET or NETWORK SERVICE account /// to write /// </summary> private void DoSomeFileWritingStuff() { Debug.WriteLine("Writing to file..."); try { using( StreamWriter writer = new StreamWriter(LOG_FILE, true) ) { writer.WriteLine("Cache Callback: {0}", DateTime.Now); writer.Close(); } } catch( Exception x ) { Debug.WriteLine( x ); } Debug.WriteLine("File write successful"); } /// <summary> /// Test database connectivity /// </summary> private void DoSomeDatabaseOperation() { Debug.WriteLine("Connecting to database..."); using( SqlConnection con = new SqlConnection(CONNECTION_STRING) ) { con.Open(); using( SqlCommand cmd = new SqlCommand( "INSERT INTO ASPNETServiceLog VALUES (@Message, @DateTime)", con ) ) { cmd.Parameters.Add("@Message", SqlDbType.VarChar, 1024).Value = "Hi I'm the ASP NET Service"; cmd.Parameters.Add("@DateTime", SqlDbType.DateTime).Value = DateTime.Now; cmd.ExecuteNonQuery(); } con.Close(); } Debug.WriteLine("Database connection successful"); } /// <summary> /// Test email send /// </summary> private void DoSomeEmailSendStuff() { try { MailMessage msg = new MailMessage(); msg.From = "abc@cde.fgh"; msg.To = "ijk@lmn.opq"; msg.Subject = "Reminder: " DateTime.Now.ToString(); msg.Body = "This is a server generated message"; SmtpMail.Send( msg ); } catch( Exception x ) { Debug.WriteLine( x ); } } /// <summary> /// Test MSMQ /// </summary> private void DoSomeMSMQStuff() { using( MessageQueue queue = new MessageQueue(MSMQ_NAME) ) { queue.Send(DateTime.Now); queue.Close(); } } protected void Session_Start(Object sender, EventArgs e) { } protected void Application_BeginRequest(Object sender, EventArgs e) { // If the dummy page is hit, then it means we want to add another item // in cache if( HttpContext.Current.Request.Url.ToString() == DummyPageUrl ) { // Add the item in cache and when succesful, do the work. RegisterCacheEntry(); } } protected void Application_EndRequest(Object sender, EventArgs e) { } protected void Application_AuthenticateRequest(Object sender, EventArgs e) { } protected void Application_Error(Object sender, EventArgs e) { Debug.WriteLine( Server.GetLastError() ); } protected void Session_End(Object sender, EventArgs e) { } protected void Application_End(Object sender, EventArgs e) { } #region Web Form Designer generated code /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> private void InitializeComponent() { this.components = new System.ComponentModel.Container(); } #endregion } }
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