msgbox error ค่ะ ฟ้อง error แบบนี้ค่ะ Showing a modal dialog box or when the application is not running in UserInteractive mode is not a valid operation. Specify the ServiceNotification or DefaultDesktopOnly

using System; 

using Microsoft.VisualBasic; 

using System.Text; 

using System.Collections; 

using System.Web; 

using System.Web.UI; 

using System.Web.UI.WebControls; 

  


namespace TestWebMsgApp 

{ 

      public class WebMsgBox 

      { 

            protected static Hashtable handlerPages = new Hashtable();             

            private WebMsgBox() 

            { 

            } 

  

            public static void Show(string Message) 

            { 

                  if (!(handlerPages.Contains(HttpContext.Current.Handler))) 

                  { 

                        Page currentPage = (Page)HttpContext.Current.Handler; 

                        if (!((currentPage == null))) 

                        { 

                              Queue messageQueue = new Queue(); 

                              messageQueue.Enqueue(Message); 

                              handlerPages.Add(HttpContext.Current.Handler, messageQueue); 

                              currentPage.Unload += new EventHandler(CurrentPageUnload); 

                        } 

                  } 

                  else 

                  { 

                        Queue queue = ((Queue)(handlerPages[HttpContext.Current.Handler])); 

                        queue.Enqueue(Message); 

                  } 

            } 

  

            private static void CurrentPageUnload(object sender, EventArgs e) 

            { 

                  Queue queue = ((Queue)(handlerPages[HttpContext.Current.Handler])); 

                  if (queue != null) 

                  { 

                        StringBuilder builder = new StringBuilder(); 

                        int iMsgCount = queue.Count; 

                        builder.Append("<script language='javascript'>"); 

                        string sMsg; 

                        while ((iMsgCount > 0)) 

                        { 

                              iMsgCount = iMsgCount - 1; 

                              sMsg = System.Convert.ToString(queue.Dequeue()); 

                              sMsg = sMsg.Replace("\"", "'"); 

                              builder.Append("alert( \"" + sMsg + "\" );"); 

                        } 

                        builder.Append("</script>"); 

                        handlerPages.Remove(HttpContext.Current.Handler); 

                        HttpContext.Current.Response.Write(builder.ToString()); 

                  } 

            } 

      } 

  

}