Maintain GridView Scroll Position and Header Inside UpdatePanel

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Introduction

For most kind of web development, we mostly need to show data inside a GridView. Suppose we need to show 500 records inside a GridView and when the user selects a record, the details are displayed in the bottom or any where else in the page. Now for preventing postback for such operations, generally we use the AJAX UpdatePanel and put the GridView inside the UpdatePanel. This will resolve the problem of postback, but then what happens? When you want to check record 100, you just scroll down the records and select the record for checking the details, and now you get the records inside your details area, but look at the GridView scroll position. Ohhhh...no, it should not be happening: it is back at the top of the records. We have to now solve this problem at the time of partial postback of the page.

Problem Statement

Here I am going to describe the actual problem in detail:

This is quite a frustrating scenario for the user. We have a good solution for that by handling the partial post back of the page.

The Solution

When we are using an UpdatePanel, we need more control on the UpdatePanel to solve this problem. For that, we need to use the Sys.WebForms.PageRequestManager class. This is used to manage the partial-page update by using client-side script. We do not need to create an object of the PageRequestManager class directly. For this solution, I have used two events. beginRequest is raised before processing of the asynchronous postback starts. Here I have just retrieved the Div position of the scroll and stored it in a variable. endRequest is raised after an asynchronous postback is finished and control has been returned to the browser. Here I have just assigned the retrieved scroll position to the div again. For more info, click here.

Using the Code

I have written the following JavaScript code for handling the partial postback, which handles the Div scroll position during the postback of the GridView inside the UpdatePanel:

<script language="javascript" type="text/javascript">
// This Script is used to maintain Grid Scroll on Partial Postback
var scrollTop;
//Register Begin Request and End Request 
Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequestHandler);
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);
//Get The Div Scroll Position
Function BeginRequestHandler(sender, args) 
{
var m = document.getElementById('divGrid');
scrollTop=m.scrollTop;
}
//Set The Div Scroll Position
function EndRequestHandler(sender, args)
{
var m = document.getElementById('divGrid');
m.scrollTop = scrollTop;
} 
</script>

Following is the code for the GridView. The Gridview should be placed inside an UpdatePanel and a Div control. The Div allow us to scroll the GridView.

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<div id="divGrid" style="overflow: auto; height: 130px"> 
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" CellPadding="4"
DataSourceID="SqlDataSource1" ForeColor="#333333" GridLines="None" Width="235px"
OnSelectedIndexChanged="GridView1_SelectedIndexChanged">
<FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
<HeaderStyle CssClass="HeaderFreez" />
<Columns>
<asp:BoundField DataField="Roll" HeaderText="Roll" SortExpression="Roll" />
<asp:BoundField DataField="Name" HeaderText="Name" SortExpression="Name" />
<asp:BoundField DataField="Langauge" HeaderText="Language" SortExpression="Langauge" />
<asp:CommandField ShowSelectButton="True" />
</Columns>
<PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
<SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
<HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<EditRowStyle BackColor="#999999" />
<AlternatingRowStyle BackColor="White" ForeColor="#284775" />
</asp:GridView>
</div>
<asp:SqlDataSource ID="SqlDataSource1" runat="server" 
ConnectionString="<%$ ConnectionStrings:DotNetRnDDBConnectionString %>"
SelectCommand="SELECT * FROM [StudDetails]"></asp:SqlDataSource>
</ContentTemplate>
</asp:UpdatePanel>

Here is the CSS code which is used to freeze the Header of the GridView. Just add this class as a HeaderStyle class of the Gridview. This will freeze the grid's header. We can use it in other cases where we need to freeze the header.

.HeaderFreez
{
   position:relative ;
   top:expression(this.offsetParent.scrollTop);
   z-index: 10;
}

Reference

• MSDN Help

History

• Written on 17-Oct-2008.