Tanweer Akhtar

Introduction

A scalable web application uses paging techniques to load large data. Paging enables a web-application to efficiently retrieve only the specific rows it needs from the database, and avoid having to pull back dozens, hundreds, or even thousands of results to the web-server. Today I am going to demonstrate how a custom paging can be implemented in asp.net application. It is a very essential approach to use paging technique in applications where lot of data to be loaded from database. Using a good paging technique can lead to significant performance wins within your application (both in terms of latency and throughput), and reduce the load on your database.

Background

GridView has built-in support for paging but it is very heavy and costly when it comes to deal large amount of data. The idea to develop a custom paging comes from stackoverflow website where lot of data are being divided into many page using custom paging technique very smoothly.

Using the code

First of all the big magic here is the SQL Query which makes it easy to handle the amount of data to be fetch from database. I used the NorthWinddatabase's Orders table which has over 800 records. Here Index and Size are two integer variables which are comes from querystring.

Index is the current page number
Size is the no of records to be shown on a page

select * from (SELECT ROW_NUMBER() OVER (ORDER BY CustomerID asc) as row,* FROM Orders) tblTemp

WHERE row between (" + index + " - 1) * " + size + " + 1 and " + index + "*" + size + " ";

SQL += " select COUNT(*) from Orders

First time when the page loads it has no querystring values so the default Index is 1 and Size is 10. You can latter change the page size, there are options for 10 records per page and 15 records per page. I tried to explain all necessary points within the code.

///Auther: Tanweer Akhtar

///Date: 26-06-2012

///Email: tanweer_bravi@yahoo.com

///License Copyright@tanweerbravi

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Data;

using System.Data.SqlClient;

using System.Web.UI.HtmlControls;

using System.Collections;

using System.Configuration;

public partial class _Default : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

int size = 0; int index = 0;

if (!Page.IsPostBack)

{

//set the page size and current page number here, default is 10 and 1 respectively

size = string.IsNullOrEmpty(Request["Size"]) ? 10 : Convert.ToInt32(Request["Size"]);

index = string.IsNullOrEmpty(Request["Index"]) ? 1 : Convert.ToInt32(Request["Index"]);

//load data from database

BindGrid(size, index);

//////////////////////////////////////////////////////

if (size == 10)

A1.Attributes.Add("class", "page-numbers current");

else if(size==15)

A2.Attributes.Add("class", "page-numbers current");

}

void BindGrid(int size, int index)

{

//page url--get from Web.config file--------change it as your page URL

string url = ConfigurationManager.AppSettings["URL"].ToString();

//string templates for links

string link = "<a href='" + url + "?Index=##Index##&Size=##Size##'><span class='page-numbers'>##Text##</span></a>";

string link_pre = "<a href='" + url + "?Index=##Index##&Size=##Size##'><span class='page-numbers prev'>##Text##</span></a>";

string link_next = "<a href='" + url + "?Index=##Index##&Size=##Size##'><span class='page-numbers next'>##Text##</span></a>";

try

{

//the connectionstring from Web.config file--------change it as per your database settings

String ConnStr = ConfigurationManager.ConnectionStrings["myConnection"].ToString();

//the sql query with paging logics

//here table name is "Orders" change this name as your requirement.

//"CustomerID" is the column by which you can sort the records, change it as per your requirement

String SQL = @"select * from (SELECT ROW_NUMBER() OVER (ORDER BY CustomerID asc) as row,* FROM Orders) tblTemp

WHERE row between (" + index + " - 1) * " + size + " + 1 and " + index + "*" + size + " ";

SQL += " select COUNT(*) from Orders";

//fetching data from database suing SqlDataAdapter Fill method to bind the Gridview

SqlDataAdapter ad = new SqlDataAdapter(SQL, ConnStr);

DataSet ds = new DataSet();

ad.Fill(ds);

//bind the grid with the ist data table---------remember that this dataset consist of two data tables

this.gvPaging.DataSource = ds.Tables[0];

this.gvPaging.DataBind();

////////get the n number of record///////////

Double n = Convert.ToDouble(Convert.ToInt32(ds.Tables[1].Rows[0][0]) / size);

/////////setting page numbers with links

if (index != 1)

lblpre.Text = link_pre.Replace("##Size##", size.ToString()).Replace("##Index##", (index - 1).ToString()).Replace("##Text##", "prev");

else

lblpre.Text = "<span class='page-numbers prev'>prev</span>";

if (index != Convert.ToInt32(n))

lblnext.Text = link_next.Replace("##Size##", size.ToString()).Replace("##Index##", (index + 1).ToString()).Replace("##Text##", "next");

else

lblnext.Text = "<span class='page-numbers next'>next</span>";

//generate dynamic paging

int start;

if (index <= 5) start = 1;

else start = index - 4;

for (int i = start; i < start + 7; i++)

{

if (i > n) continue;

//create dynamic HyperLinks

HyperLink lnk = new HyperLink();

lnk.ID = "lnk_" + i.ToString();

if (i == index)//current page

{

lnk.CssClass = "page-numbers current";

lnk.Text = i.ToString();

}

else

{

lnk.Text = i.ToString();

lnk.CssClass = "page-numbers";

lnk.NavigateUrl = url + "?Index=" + i + "&Size=" + size + "";

}

//add links to page

this.pl.Controls.Add(lnk);

}

//------------------------------------------------------------------

//set up the ist page and the last page

if (n > 7)

{

if (index <= Convert.ToInt32(n / 2))

{

lblLast.Visible = true;

lblIst.Visible = false;

lblLast.Text = link.Replace("##Index##", n.ToString()).Replace("##Size##", size.ToString()).Replace("##Text##", n.ToString());

spDot2.Visible = true;

spDot1.Visible = false;

}

else

{

lblLast.Visible = false;

lblIst.Visible = true;

lblIst.Text = link.Replace("##Index##", (n - n + 1).ToString()).Replace("##Size##", size.ToString()).Replace("##Text##", (n - n + 1).ToString());

spDot2.Visible = false;

spDot1.Visible = true;

}

catch (Exception ee)

{

//catch the exception

}

In the above method you have to change the Config settings like the Connectionstring and page url which can be edited in the web.config file.

On the aspx page there are six labels:

previous page link
ist page link
dot before ist page link
next page link
last page link
dot before ist page link

and a PlaceHolder for other page numbers

<div>

<asp:GridView ID="gvPaging" runat="server" AutoGenerateColumns="false" GridLines="None">

<asp:TemplateField>

<table>

<tr>

Customer ID:

</td>

<%# Eval("CustomerID")%>

</td>

</tr>

<tr>

Employee ID:

</td>

<td>

<%# Eval("EmployeeID") %>

</td>

Ship Name:

</td>

<td>

<%# Eval("ShipName")%>

</td>

Ship Country:

</td>

<td>

<%# Eval("ShipCountry")%>

</td>

</tr>

<tr>

<hr />

</td>

</tr>

</table>

</ItemTemplate>

</asp:TemplateField>

</Columns>

</asp:GridView>

<asp:Label runat="server" ID="lblpre"></asp:Label>

<asp:Label runat="server" ID="lblIst" Visible="false"></asp:Label>

<asp:Label runat="server" ID="spDot1" CssClass="page-numbers prev" Visible="false"

Text="..."></asp:Label>

<asp:PlaceHolder ID="pl" runat="server"></asp:PlaceHolder>

<asp:Label runat="server" ID="spDot2" Visible="false" CssClass="page-numbers prev"

Text="..."></asp:Label>

<asp:Label runat="server" ID="lblLast" Visible="false"></asp:Label>

<asp:Label runat="server" ID="lblnext"></asp:Label>

</div>

<a href="javascript:void(0);" id="A2" runat="server" class="page-numbers">15</a><span

class="page-numbers desc">per page</span>

</div>

HyperLinks are dynamically created and set their Links and css and add in the placeholder at page load.

Another important point is to replace the Table name in the sql Query and the column name in the order by statement.

To change the page size there are two options(html anchor tags) on the right side of the page. You can set 10 records per page or 15 records per page. Using JQuery I capture the click events of these two html anchors and set the currently set page size in a HiddenField and reload the current page by passing Index and Size in querystring.

jQuery Code:

$(document).ready(function () {

$('#A1').click(function () {

$('#hdSize').val('10');

Loadpage();

});

$('#A2').click(function () {

$('#hdSize').val('15');

Loadpage();

});

function Loadpage() {

try {

//reload page using new page size

var url = $(location).attr('href');

var index = "Index=1";

if (url.indexOf('Index') > 0) {

index = url.split('?')[1];

index = index.split('&')[0];

}

url = url.split('?')[0] + "?" + index + "&Size=" + $('#hdSize').val() + "";

window.location.href = url;

} catch (e) {

alert(e);

}

</script>

CSS: CSS plays an important role in this paging. Although all works done but these all looks very poor untill a good css effect is given.

{

color: #55ff00;

}

.text

{

color: #74aacc;

}

.fl

{

float: left;

}

.f2

{

float: right;

padding-right: 200px;

}

.pager

{

margin-top: 20px;

margin-bottom: 20px;

}

.page-numbers

{

font-family: 'Helvetica Neue' ,Helvetica,Arial,sans-serif;

border: 1px solid #CCC;

color: #808185;

display: block;

float: left;

font-size: 130%;

margin-right: 3px;

padding: 4px 4px 3px;

text-decoration: none;

}

.page-numbers.current

{

background-color: #808185;

border: 1px solid #808185;

color: white;

font-weight: bold;

}

.page-numbers.next, .page-numbers.prev

{

border: 1px solid white;

}

.page-numbers.desc

{

border: none;

margin-bottom: 10px;

}

Screenshot

History

It took a whole week to develop this article and ist release date is 26th June 2012

Tanweer Akhtar

Tuesday, 26 June 2012

Custom paging with ASP.NET GridView