How to avoid adding repeat submit the same data if you click the 'Refresh' button of Browser?

After reading this book(Programming Microsoft ASP.NET 2.0 Applications - Advanced Topics), I get some ideas about this issue.

Usually, we may need to avoid doing the repeat operation when the user click the 'Refresh' button of Browser. How to prevent it?

Actually, we can save the operation times for each request page in HashTable in Custom HttpModule.

   DownLoad

//Page

using  System;
using  System.Web;
using  System.Web.UI;

namespace  ProAspNet20.Advanced.CS.Components
{
     public   class  Page : System.Web.UI.Page
    {
         #region  New Properties

         public   bool  IsRefreshed 
        {
             get
            {
                 object  o  =  HttpContext.Current.Items[RefreshAction.PageRefreshEntry];
                 if  (o  ==   null )
                     return   false ;
                 return  ( bool ) o;
            }
        }
         #endregion


         #region  Overrides
         //  **************************************************************
         //  Handle the PreRenderComplete event
         protected   override   void  OnPreRenderComplete(EventArgs e)
        {
             base .OnPreRenderComplete(e);
            SaveRefreshState();
        }
         #endregion


         #region  Helpers
         //  **************************************************************
         //  Create the hidden field to store the current request ticket
         private   void  SaveRefreshState()
        {
             int  ticket  =  ( int )HttpContext.Current.Items[RefreshAction.NextPageTicketEntry];
            ClientScript.RegisterHiddenField(RefreshAction.CurrentRefreshTicketEntry, 
                ticket.ToString());
        }
         #endregion
    }
}

//Reresh Action

using  System;
using  System.Web;
using  System.Collections;


namespace  ProAspNet20.Advanced.CS.Components
{
     public   class  RefreshAction
    {
         #region  Constants
         //  ***********************************************************
         //  Constants
         public   const   string  LastRefreshTicketEntry  =   " __LASTREFRESHTICKET " ;
         public   const   string  CurrentRefreshTicketEntry  =   " __CURRENTREFRESHTICKET " ;
         public   const   string  PageRefreshEntry  =   " IsRefreshed " ;
         public   const   string  NextPageTicketEntry  =   " __NEXTPAGETICKET " ;
         #endregion

         static  Hashtable requestHistory  =   null ;

         //  ***********************************************************
         //  Manage to check if the F5 button has been pressed
         public   static   void  Check(HttpContext ctx)
        {
             //  Initialize the ticket slot
            EnsureRefreshTicket(ctx);

             //  Read the last ticket served in the session (from Session)
             int  lastTicket  =  GetLastRefreshTicket(ctx);

             //  Read the ticket of the current request (from a hidden field)
             int  thisTicket  =  GetCurrentRefreshTicket(ctx, lastTicket);

             //  Compare tickets
             if  (thisTicket  >  lastTicket  ||  
                (thisTicket == lastTicket  &&  thisTicket == 0 ))
            {
                UpdateLastRefreshTicket(ctx, thisTicket);
                ctx.Items[PageRefreshEntry]  =   false ;
            }
             else
            {
                ctx.Items[PageRefreshEntry]  =   true ;
            }
        }
         
         //  ***********************************************************
         //  Initialize the internal data store 
         private   static   void  EnsureRefreshTicket(HttpContext ctx)
        {
             //  Initialize the session slots for the page (Ticket) and the module (LastTicketServed)
             if  (requestHistory  ==   null )
                requestHistory  =   new  Hashtable();
        }


         //  ***********************************************************
         //  Return the last-served ticket for the URL
         private   static   int  GetLastRefreshTicket(HttpContext ctx)
        {
             //  Extract and return the last ticket
             if  ( ! requestHistory.ContainsKey(ctx.Request.Path))
                 return   0 ;
             else
                 return  ( int ) requestHistory[ctx.Request.Path];
        }
        

         //  ***********************************************************
         //  Return the ticket associated with the page
         private   static   int  GetCurrentRefreshTicket(HttpContext ctx,  int  lastTicket)
        {
             int  ticket;
             object  o  =  ctx.Request[CurrentRefreshTicketEntry];
             if  (o  ==   null )
                ticket  =  lastTicket;
             else
                ticket  =  Convert.ToInt32(o);

            ctx.Items[RefreshAction.NextPageTicketEntry]  =  ticket  +   1 ;
             return  ticket;
        }
        

         //  ***********************************************************
         //  Store the last-served ticket for the URL
         private   static   void  UpdateLastRefreshTicket(HttpContext ctx,  int  ticket)
        {
             //  Item overwrites, Add does not
            requestHistory[ctx.Request.Path]  =  ticket;
        }
    }
}

//RereshModule

using  System;
using  System.Web;
using  System.Web.SessionState;


namespace  ProAspNet20.Advanced.CS.Components
{
     public   class  RefreshModule : IHttpModule
    {
         #region  IHttpModule
         //  ***********************************************************
         //  IHttpModule::Init
         public   void  Init(HttpApplication app)
        {
             //  Register for pipeline events
            app.BeginRequest  +=   new  EventHandler( this .OnAcquireRequestState);
        }
         //  ***********************************************************
         //  IHttpModule::Dispose
         public   void  Dispose() 
        {
        }
         #endregion


         #region  Helpers
         //  ***********************************************************
         //  Determine if a F5 or back/fwd action is in course
         private   void  OnAcquireRequestState( object  sender, EventArgs e)
        {
             //  Get access to the HTTP context 
            HttpApplication app  =  (HttpApplication)sender;
            HttpContext ctx  =  app.Context;

             //  Check F5 action
            RefreshAction.Check(ctx);

             return ;
        }
         #endregion
    }
}

//TestRefresh

<% @ Page Language = " C# "  AutoEventWireup = " true "  CodeFile = " TestRefresh.aspx.cs "  Inherits = " TestRefresh "   %>

<! DOCTYPE html PUBLIC  " -//W3C//DTD XHTML 1.1//EN "   " http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd " >

< html xmlns = " http://www.w3.org/1999/xhtml "   >
< head runat = " server " >
     < title > Test Refresh </ title >
</ head >
< body >
         < form id = " Form1 "  method = " post "  runat = " server " >
             < table border = " 2 " >
                 < tr >
                     < td bgcolor = " yellow "  rowspan = " 2 " >
                         < h1 id = " Msg "  runat = " server " ></ h1 >
                     </ td >
                 </ tr >
             </ table >
             < hr >
             < asp:textbox id = " FName "  runat = " server "  text = " Dino "   />
             < asp:textbox id = " LName "  runat = " server "  text = " Esposito "   />< br >
             < asp:button id = " AddContactButton "  runat = " server "  text = " Add Contact "  Font - Bold = " True "  OnClick = " AddContactButton_Click " ></ asp:button >< asp:button id = " ResetButton "  runat = " server "  text = " Clear Contacts "  Font - Bold = " True "  OnClick = " ResetButton_Click " ></ asp:button >
             < br >
             < a target = " _blank "  href = " TestRefresh.aspx " > Display a copy of me </ a >
             < hr >
             & nbsp; < asp:GridView ID = " grid "  runat = " server " >
             </ asp:GridView >
         </ form >
</ body >
</ html >

//Code

using  System;
using  System.Data;
using  System.Configuration;
using  System.Collections;
using  System.Web;
using  System.Web.Security;
using  System.Web.UI;
using  System.Web.UI.WebControls;
using  System.Data.OleDb;

public   partial   class  TestRefresh : ProAspNet20.Advanced.CS.Components.Page
{
     protected   void  AddContactButton_Click( object  sender, EventArgs e)
    {
        Msg.InnerText  =   " Added " ;
         if  ( ! this .IsRefreshed)
            AddRecord(FName.Text, LName.Text);
         else
            Msg.InnerText  =   " Page refreshed " ;
    }

     protected   void  ResetButton_Click( object  sender, EventArgs e)
    {

    }

     #region  Helpers
     private   void  AddRecord( string  fname,  string  lname)
    {
        
    }

     private   void  BindData()
    {
         
    }
     #endregion

}

 //web.config

< httpModules >
       < add  name ="ScriptModule"  type ="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
       < add  name ="Refresh"  type ="ProAspNet20.Advanced.CS.Components.RefreshModule,ProAspCompLib" />
</ httpModules >