Imports System.Text
Imports System.Collections.Queue
Imports System.Web.UI.Page
Imports System
Imports System.Web.UI
Imports System.Web
Imports System.Collections
Public Class MessageBox
   Private Shared m_executingPages As Hashtable = New Hashtable

   Private Sub New()
   End Sub

   Public Shared Sub Show(ByVal sMessage As String)
       If Not m_executingPages.Contains(HttpContext.Current.Handler) Then
           Dim executingPage As Page = CType(HttpContext.Current.Handler, Page)
           If Not (executingPage Is Nothing) Then
               Dim messageQueue As Queue = New Queue
               messageQueue.Enqueue(sMessage)
               m_executingPages.Add(HttpContext.Current.Handler, messageQueue)
               AddHandler executingPage.Unload, AddressOf ExecutingPage_Unload
           End If
       Else
           Dim queue As Queue = CType(m_executingPages(HttpContext.Current.Handler), Queue)
           queue.Enqueue(sMessage)
       End If
   End Sub

   Private Shared Sub ExecutingPage_Unload(ByVal sender As Object, ByVal e As EventArgs)
       Dim queue As Queue = CType(m_executingPages(HttpContext.Current.Handler), Queue)
       If Not (queue Is Nothing) Then
           Dim sb As StringBuilder = New StringBuilder
           Dim iMsgCount As Integer = queue.Count
           sb.Append("<script language='javascript'>")
           Dim sMsg As String
           While System.Math.Max(System.Threading.Interlocked.Decrement(iMsgCount), iMsgCount + 1) > 0
               sMsg = CType(queue.Dequeue, String)
               sMsg = sMsg.Replace("" & Microsoft.VisualBasic.Chr(10) & "", "\n")
               sMsg = sMsg.Replace("""", "'")
               sb.Append("alert( """ + sMsg + """ );")
           End While
           sb.Append("</script>")
           m_executingPages.Remove(HttpContext.Current.Handler)
           HttpContext.Current.Response.Write(sb.ToString)
       End If
   End Sub
End Class