Saturday, March 24, 2012

Paging using DataGrid and DataList (referring to ScottGus paging tutorial)

I have a webpage that uses a Datalist adapted from ScottGu's example at It does not seem to benefit from Ajax partial updates (update panel), since as it pages, it actually asks for different pages' urls, etc...(Please see ScottGu's fantastic tutorial there for more details).

Question: If I use a DataGrid that has paging turned on, will it (magically) perform the operations mentioned in Scott's article, that is, sending only that data through each page request that is pertinet to that page?

Question 2 There is a slim chance that ASP.Net Ajax is actually so smart as to do what I said above, however, I need a DataList (for formatting reasons) that does not have paging .

Is there a way for the paging mentioned in ScottGu's article to be applied to the asynchornous paging, and for the paging control on the page (a hyperlink) to fetch data from that stored "stash"?



Dogs Rule!

Just glancing through Scott's post, it doesn't look like this will "just work" inside an UpdatePanel, because as you mention, it's requesting a new page URL with the page number in the query string.

To get something like this to work, you'd need to first convert it to use postbacks instead of page navigation. (So change the hyperlink to a HyperLinkButton and pass the page number as an argument to the event handler instead of as a query string parameter.)

Basically, if you have a page that works with postbacks, it should be easy to use UpdatePanels to get AJAX functionality. If you have navigation, however (new URLs), then the UpdatePanel won't help you.

View this code

Sub BindData()
Dim mydt As New yourdatable()
Dim tba As NewyourobjectTableAdapters.yourtableadaper()

tba.Fill(mydt, Me
dgPager.CurrentPageIndex * Me.dgPager.PageSize , Me.dgPager.PageSize)

Me.dgPager.VirtualItemCount = yourqueryrecordcount

dgPager.DataSource = mydt

Me.DataList1.DataSource = mydt

End Sub

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
If Not Page.IsPostBack Then

End If
End Sub

Protected Sub dgPager_ItemCreated(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DataGridItemEventArgs)
If e.Item.ItemType = ListItemType.Item Or e.Item.ItemType = ListItemType.AlternatingItem Then
e.Item.Visible = False
End If

End Sub

ProtectedSub dgPager_PageIndexChanged(ByVal source As Object, ByVal e AsSystem.Web.UI.WebControls.DataGridPageChangedEventArgs)
Me.dgPager.CurrentPageIndex = e.NewPageIndex

End Sub
ASPX page

<form id="form1" runat="server">
<asp:DataList ID="DataList1" runat="server" RepeatColumns="4" RepeatDirection="Horizontal">
<%# Eval("YourDataField") %><br />
<asp:DataGridID="dgPager" runat="server" AllowPaging="True"AutoGenerateColumns="False" GridLines="None" PageSize="8"ShowHeader="False" OnPageIndexChanged="dgPager_PageIndexChanged"OnItemCreated="dgPager_ItemCreated" AllowCustomPaging="True">
<PagerStyle Mode="NumericPages" />


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