Custom ASP.NET Datagrid Paging With Exact Count

About this Custom Paging...

In a previous article, not the same as the custom paging mentioned in Paging Database Results in ASP.NET, the author (Scott Mitchell) mentioned one downside of the default paging behavior of the DataGrid Web control was that, for each page, all of the database records to be paged through were returned to the ASP.NET Web page, even if only a small portion of them were displayed. Furthermore, the author mentioned that this potential bottleneck could be overcome with custom paging. The custom paging the author was referring to was the custom paging supported by the DataGrid Web control. This article looks at how to implement one's own custom paging - this form of custom paging still suffers from the same limitation as the default DataGrid paging.

Introduction
Anybody in the DB world knows what paging database results is and its effect. From the time I had started getting into good old classic ASP, I was intrigued with the ability to divide large sets of data into sections of x records per page. One thing that I didn't like about paging is that it seemed sites incorporated just a < Prev and Next > link on the search results page. I wasn't satisfied with such a lackluster paging technique, and from there I searched high and low on every ASP Web site I could find to see if there was code to show more advanced paging options, such as how many pages were remaining to be paged through, or, if the next page was the last page of results, how many records were on that last page. Unfortunately, I couldn't find any such code, so I had set out to do it myself. (To see the proposed paging enhancements I like, check out the live demo for this article...)

I have since coded a number of techniques for advanced paging in classic ASP, but my latest challenge has been to incorporate the same paging techniques in ASP.NET! (For more information on ASP.NET, be sure to visit the ASP.NET Article Index.) Pssst, don't ask me to talk about redoing my app in Beta 1, and upon upgrading to Beta 2 was horrified that my code needed to be redone.... by the way, the code in this article is all Beta 2 compliant.

Now, if anyone has looked into the Microsoft .NET SDK and Quickstart samples you will find custom paging samples, but it's the usual next and prev stuff. Now let's see how we can kick this paging up a notch and tell us more detail about our data output.

Accessing our Data
The first step is of course to query our database, and send our data into our datagrid. The first thing we should concern ourselves with in any .Net page is that we import the necessary namespaces for our app. In this case, as with most data access apps, I'm importing System.Data and System.Data.SqlClient for SQL Server. If you use MS Access or another database then System.Data.OleDb namespace and associated classes will work just fine, providing you modify the connection variables and data adapters.

This importing of namespaces is all done before our script tags like so:

<%@ Import Namespace = "System.Data" %> <%@ Import Namespace = "System.Data.SqlClient" %>

Now, within our server-side script tags we include our object-oriented stuff – our Subroutine to access our database and bind our result set into our ASP.NET Datagrid. This subroutine, BindSQL() needs to first create all of our variables that we'll use:

Sub BindSQL() Dim MyConnection As SqlConnection Dim DS as DataSet Dim MyCommand As SqlDataAdapter Dim RcdCount As Integer 'Our SQL string Dim sqlStr As String = "SELECT titles.title, authors.au_lname, " & _ "authors.au_fname, titles.price " & _ "FROM authors INNER JOIN titleauthor ON " & _ "authors.au_id = titleauthor.au_id " & _ "INNER JOIN titles ON " & _ "titleauthor.title_id = titles.title_id" 'The connection to our database Dim strConn As String = "server=(local);uid=sa;pwd=;" & _ "database=pubs;Trusted_Connection=yes;"

Next we need to instantiate our connection and command object, and the fill our DataSet object with the results of the SQL query:

... 'Open up our connection with our connection object MyConnection = New SQLConnection(strConn) 'To execute our Sql Statement and provide our active connection MyCommand = NewSqlDataAdapter(sqlStr, MyConnection) 'Create instance of DataSet object and fill our predetermined 'datagrid with it and we name it DS = new DataSet() MyCommand.Fill(DS, "pubs") ...

Now comes the one part that we'll used for our custom paging – the record count, and you'll see it quite different than our classic ASP way.

RcdCount = DS.Tables("pubs").Rows.Count.ToString()

Now that we have this total count of the records in the DataSet, we'll save it to a global variable, since we'll want to access it from other subroutines. The variable ResultCount should be defined in global-scope, as an Integer. (See the complete source later on in this article to note how to create global-scoped variables)

ResultCount = RcdCount

Next, we display the number of records found in a label control:

RecordCount.Text = "<b><font color=red>" & RcdCount & "</font> records found"

Finally, at this point, we can bind our DataSet to the DataGrid and display a label illustrating what page of results we're currently viewing: which will display :

Pubs.DataSource = DS   Pubs.Databind()   lblPageCount.Text = "Page " & Pubs.CurrentPageIndex + 1 & " of " & Pubs.PageCount

At this point, we need to determine if we need to show the Next/Prev links, as well as the First Page/Last Page links:

'Do we want to show the prev/First Page buttons? If Pubs.CurrentPageIndex <> 0 Then Call Prev_Buttons() Firstbutton.Visible = true Prevbutton.Visible = true Else Firstbutton.Visible = false Prevbutton.Visible = false End If 'Do we want to show the Next/Last Page buttons? If Pubs.CurrentPageIndex <> (Pubs.PageCount-1) then Call Next_Buttons() NextButton.Visible = true Lastbutton.Visible = true Else NextButton.Visible = false Lastbutton.Visible = False End If End Sub

That concludes our BindSQL() subroutine, which is a bit lengthy. Don't worry, that's, by far, the most complex piece of our ASP.NET Web page! We still have three more short server-side subroutines to examine, but let's first look at the HTML portion of our ASP.NET Web page, which we'll do in Part 2.