Do I need to re-retrieve data when paging using asp:GridView

I have a .aspx search screen that displays the results of the search in an asp:GridView component. There can be up to approx 1000 records returned by the search. I want to implememt paging on the grid so that only 15 records are displayed at any one time and the user can page through the results.

I am retrieving the records by passing search parameters to a WCF service which returns a List of particular entity objects. I create a Datatable and insert one DataRow per entity object from the List. I then bind the grid view to the Datatable.

This is how my grid is defined in the .aspx page:

<asp:GridView ID="gridCat" runat="server" AutoGenerateColumns="False" DataKeyNames="CatalogueID" 
   HeaderStyle-CssClass="fieldHeading" RowStyle-CssClass="fieldContent" 
    AlternatingRowStyle-CssClass="alternateFieldContent" Width="100%" 
    AllowPaging="True" AllowSorting="True" AutoGenerateDeleteButton="True" 
    PageSize="15">

and I also have this method in the code behind (.aspx.vb file):

    Sub GridPagingAction(ByVal sender As Object, ByVal e As GridViewPageEventArgs) Handles gridCat.PageIndexChang开发者_高级运维ing
    gridCat.PageIndex = e.NewPageIndex
    gridCat.DataBind()
    gridCat.Visible = True
End Sub

My problem is this: the first page is rendered correctly i.e. the first 15 records are displayed correctly. However, when I navigate to page 2 in the grid, the GridPagingAction method is hit on the server but nothing is displayed in the grid - it is just blank.

I think the reason this is happening is because the Datatable no longer exists on the server when the request for the second page hits the server - is that right? And the asp:GridView, when it is rendering the first page of results, only takes the first 15 records from the Datatble and sends them back to the browser. So when the request for the second page comes in the other records (i.e. records 16 - 1000) don't exist anywhere - is all that correct?

If so, what's the best solution - I can't see how to implement paging without having to do one of the following:

1. re-perform the search each time the user uses the paging option;
2. saving the search results on the Session after the first Search retrieving them each time the user uses the paging option;
3. manually inserting the Search results into ViewState and retrieving them each time the user uses the paging option.

Is there a better way to do this (or am I doing it wrong)? If not, which of the 3 options do you think is the best? I'm leaning towards option 2 as I don't think option 1 is performant and I don't want to be sending loads of unnecessary data back to the browser as per option 3.

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All you said is correct. You could either use ViewState or the Session to keep hold of the data on client- or server-side, but if you really have that many records, it might be a good idea to only collect the data you actually need.

So if you want to show records 1 to 10, you perform a query against the database and only fetch those ten records. If you want to show the next ten, you perform another query with the according parameters.

This will improve your performance and memory usage significantly, IF calling your DB is not overly expensive.

This article might give you a start on how to do this: http://dotnetslackers.com/articles/gridview/Optimized-Paging-and-Sorting-in-ASP-NET-GridView.aspx

If you want an easy solution without any additional efforts, I would query all the records on each postback (your option #1). If you want the best performing solution with not much overhead, use the custom paging.