Induce Callback script on a PostBack

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BhupathiNaid...

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Induce Callback script on a PostBack

Jun 07, 2012 05:33 AM|BhupathiNaidu S|LINK

Hi All,

I have a peculiar case. the scenario is i have callback functionality implemented and a button. On Button click i modify the parameters passed to the server. please see the attached image of the script induced and when i send the alerted data, i am being being shown some text. I tried to track from where the text is being written to the browser but no luck.

prerequisite is to have Tamper IE installed to add new parameters

could you please provide me a solution to resolve the issue? i.e exception should be caught, instead of junk data written to the browser.

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

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
  <title>Client Callback Example</title>
  <script type="text/ecmascript">
    function LookUpStock()
    {
        var lb = document.getElementById("ListBox1");
        var product = lb.options[lb.selectedIndex].text;
        CallServer(product, "");
    }
    
    function ReceiveServerData(rValue)
    {
        document.getElementById("ResultsSpan").innerHTML = rValue;
        
    }
  </script>
</head>
<body>
  <form id="form1" runat="server">
    <div>
      <asp:ListBox ID="ListBox1" Runat="server"></asp:ListBox>
      <br />
      <br />
      <button type="Button" onclick="LookUpStock()">Look Up Stock</button>
      
      <br />
        <asp:Button ID="Button1" runat="server" Text="Button" onclick="Button1_Click" />
      <br />
      Items in stock: <span id="ResultsSpan" runat="server"></span>
      <br />
    </div>
  </form>
</body>
</html>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class ClientCallback : System.Web.UI.Page, System.Web.UI.ICallbackEventHandler
{
    protected System.Collections.Specialized.ListDictionary catalog;
    protected String returnValue;
    protected void Page_Load(object sender, EventArgs e)
    {

        try
        {

            String cbReference =
             Page.ClientScript.GetCallbackEventReference(this,
             "arg", "ReceiveServerData", "context");
            String callbackScript;
            callbackScript = "function CallServer(arg, context)" +
                "{ " + cbReference + ";}";
            Page.ClientScript.RegisterClientScriptBlock(this.GetType(),
                "CallServer", callbackScript, true);

            catalog = new System.Collections.Specialized.ListDictionary();
            catalog.Add("monitor", 12);
            catalog.Add("laptop", 10);
            catalog.Add("keyboard", 23);
            catalog.Add("mouse", 17);

            ListBox1.DataSource = catalog;
            ListBox1.DataTextField = "key";
            ListBox1.DataBind();

        }
        catch (Exception ex)
        {

            throw ex;
        }
    }

    public void RaiseCallbackEvent(String eventArgument)
    {

        if (catalog[eventArgument] == null)
        {
            returnValue = "-1";
        }
        else
        {
            returnValue = catalog[eventArgument].ToString();
        }


    }
    public String GetCallbackResult()
    {
        return returnValue;
    }
    protected void Button1_Click(object sender, EventArgs e)
    {

    }




}