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Wednesday, April 16, 2014
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Computer Programming : How to change data without postback in ASP.NET

12:00 AMWednesday, April 16, 2014
News From Computer Programming: In ASP.NET you can't change the data without post-back, if you want to change data without post back, you can use AJAX technology. In previous article we have already learned more about AJAX like, How to install AJAX control Toolkit to the Toolbox or many more. Today we will learn How to update your GridView data in every seconds, for this you can use Timer control.
The Timer control is used for updating contents of the UpdatePanel control at predefined intervals. Single Timer control can refresh  more than one UpdatePanel control simultaneously. The Timer control  has an Interval property for defining the timer limit after which the content gets refreshed. When this interval limit gets over, the Tick event is raised . You can handle this event for updating the content values defined in the UpdatePanel control. The Timer control can be used either inside the UpdatePanel control or outside the UpdatePanel control. Now, let's try to understand the UpdatePanel control in both ways.

Timer control Inside the UpdatePanel Control

To use the Timer control inside the UpdatePanel control, drag and drop from the Toolbox as a sub-element of the <ContentTemplate>tag and follow the following steps:
1. Set the interval property of the Timer control as 1000 that equal to 1 second as it takes value in milliseconds.
2.Now, double-click the Timer control in design mode. It will generate event handler function in the code-behind file to handle the Tick event.

Timer Control Outside the UpdatePanel Control

You can use the Timer control outside the UpdatePanel control. This approach is appropriate when there are more than one UpatePanel control in the same Web page and you need to use same Timer control for all or some of them. To do so, you need to perform some changes in your application. However, these changes will not affect the output of your application. First, drag-and-drop the Timer control from the toolbox. Drop it after the ScriptManager control and before the UpdatePanel control; and configure its properties in the following way:
The ScriptManager Tag:
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>


The Timer control outside the UpdatePanel control and after the ScriptManager Tag:
<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>

        <asp:Timer ID="Timer1" runat="server" Interval ="1000" OnTick ="Timer1_Tick"></asp:Timer>
Configure the UpdatePanel Control's <Triggers> Element for referencing the timer control in the following way:

   <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID ="Timer1" EventName ="Tick" />
            </Triggers>
        </asp:UpdatePanel>
Lets take a simple example to update GridView Data:
Step-1 : Add ScriptManager and UpdatePanel control after Form tag
Step-2 : Add Content template inside UpdatePanel Control.  
Step-3 : Add Timer control inside ContentTemplate with Tick event and Interval property.
Step-4 : Also add GridView control inside the Content Template.
Step-5 : Bind GridView Control in Tick event.
 Complete Code
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default3.aspx.cs" Inherits="Default3" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">



        <asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
       
       
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
           <ContentTemplate>



               <asp:Timer ID="Timer1" runat="server" Interval ="1000" OnTick ="Timer1_Tick"></asp:Timer>



               <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="Id" DataSourceID="SqlDataSource1">
                   <Columns>
                       <asp:BoundField DataField="Id" HeaderText="Id" InsertVisible="False" ReadOnly="True" SortExpression="Id" />
                       <asp:BoundField DataField="Name " HeaderText="Name " SortExpression="Name " />
                       <asp:BoundField DataField="Address" HeaderText="Address" SortExpression="Address" />
                   </Columns>
               </asp:GridView>

               <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>" SelectCommand="SELECT * FROM [Table]"></asp:SqlDataSource>
           </ContentTemplate>
        </asp:UpdatePanel>
    <div>
   
    </div>
    </form>
</body>
</html>
Code File
 protected void Timer1_Tick(object sender, EventArgs e)
    {
        GridView1.DataBind();
    } 
Output
Computer Programming : How to update data, without postback
in above snap, if you change data in database table from server explorer, output affected on browser. 
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