[ASP.NET 3.5] Custom Paging for ListView Control

[Bazenga]

Hello,

I'm trying to create a custom paging for a ListView I have. I don't want to use Data Pager since it relies on the viewstate and I cannot afford to fetch all records at once (1 million++ records).

I tried to read a lot of this subject but I couldn't find anything that I can use. What I currently have (since the project is still in development and not production) is the data pager inside the Layout Template for the ListView Control.

Any helps, tips are welcomed. I'm completely stuck!

[Rohdekill]

Your problem doesn't lie within the pager. It lies in the records you are retrieving. By building a more efficient search filtering front end you can retrieve fewer, more relevant results.

Build a search criteria page to allow the user to restrict the results. If the dataset is merely informational data, then filter on a default such as limit to only current year, or 6 months, or top 500.

Not only will doing the above make the end user happy, but your DB server will thank you as well.

[Bazenga]

Thanks for the input Rohdekill, but that's not what I'm looking for. I have a ListView that displays 20 records per page without any kind of filter or searching for whatever. It's a requirement and I cannot change it :-(.

[Rohdekill]

In that case, I would have a talk with someone with knowledge on servers who is involved with the project.

Obtaining such results consumes the DB processing.

If I were stuck in such a scenario, I would still cheat. I would hide the pager. I would then create a series of buttons underneath the display such as:

"Pages 1-10" "1" "2" ... "10" "Pages 11-20"

Then only grab enough results to fill 10 pages (ex. 20 results per page x 10 pages = 200 results).

Upon clicking "Pages 11-20", query and filter so you get results 201-400, and change the text of the buttons.

[Bazenga]

I actually found some code on the internet to deal with paging (a stored procedure that takes startIndex, maxdisplay ... etc ..) It worked fine, but when I use ObjectDataSource you need to supply the SelectCountMethod, and when do that the select parameters gets messed up (I think there is a bug or something since the data source cannot differentiate between the SelectMethod and the SelectCountMethod).

[Antaris Veteran]

Can we see what code you have so far, this works for me:

        <asp:ObjectDataSource 
            ID="ObjectDataSource1" 
            runat="server"
            EnablePaging="true"
            TypeName="Test.CustomerSelector"
            SelectMethod="GetPageOfCustomers"
            SelectCountMethod="GetCountOfCustomers"
            StartRowIndexParameterName="page"
            MaximumRowsParameterName="count" />

With an example selector:

    public class CustomerSelector
    {
        public List<Customer> GetPageOfCustomers(int page, int count)
        {
            return GetCustomers(count).ToList();
        }

        public int GetCountOfCustomers()
        {
            return 100;
        }

        private static IEnumerable<Customer> GetCustomers(int count)
        {
            for (int i = 0; i < count; i++)
                yield return CreateCustomer();
        }

        private static Customer CreateCustomer()
        {
            return new Customer { Title = "Mr", Forename = "Matthew", Surname = "Abbott" };
        }
    }

It's important to note that the function of the SelectCountMethod is not the same function as the SelectMethod, the SelectCountMethod simply gets the total number of entities. The SelectMethod is the method that you want called with your paging instructions.

[Bazenga]

*BUMP*.

I'm sorry for this long delay. This IS NOT WORKING AT ALL :'(. Here's the damned error that I'm always getting:

[i]ObjectDataSource 'obj' could not find a non-generic method 'GetItemsCount' that has parameters: txtSearch, letter, displayType.[/i]

this is the code that I have:

the object data source:

	<asp:ObjectDataSource ID="obj" 
 	EnablePaging="true"
 	runat="server" 
 	SelectMethod="GetItems" 
 	SelectCountMethod="GetItemsCount" 
 	MaximumRowsParameterName="pageSize" StartRowIndexParameterName="startRowIndex"
 	TypeName="App_Code.Items">
 	<SelectParameters>
 	<asp:ControlParameter ControlID="txtSearch" Name="txtSearch" PropertyName="Text" Type="String" />
 	<asp:ControlParameter ControlID="menu" Name="letter" PropertyName="SelectedValue" Type="String" />
 	<asp:ControlParameter ControlID="chk" Name="displayType" PropertyName="SelectedValue" Type="String" />
 	</SelectParameters>
	</asp:ObjectDataSource>

function signature:

public List<object> GetItems(string txtSearch, string letter, string displayType, int startRowIndex, int pageSize)
{
}

public int GetItemsCount() { return 500; }

the stored procedure:

ALTER PROCEDURE [dbo].[GetTitles]

 	@Alpha nvarchar(255),
 	@Letter nvarchar(20),
 	@DisplayType nvarchar(20),
	 @startRowIndex int,
	 @pageSize int

The object data source is bound to a ListView control if that helps? I'm getting frustrated. HELP ME!!!!!!

[sbauer]

Why are using an ObjectDataSource? Why don't you just code it yourself?

[Bazenga]

  On 24/05/2010 at 16:08, sbauer said:

Why are using an ObjectDataSource? Why don't you just code it yourself?

yeah, that's what I did :-). the problem is already solved, but I want to know why the ObjectDataSource is not differentiating between SelectMethod and SelectCountMethod. Is this a bug or something?

[Antaris Veteran]

I think the reason why it's having trouble, is that the two methods should be designed to accept the same parameters. E.g.

GetItems(string txtSearch, string letter, string displayType, int startRowIndex, int pageSize);

and

GetItemsCount(string txtSearch, string letter, string displayType);

The reason for this is you should expect the GetItemsCount method to process the same arguments as the GetItems method, because it should be providing a count of how many items the GetItems method should return. If you had a method which doesn't accept the same parameters, how can you know that the count being returned is the actual count of items from GetItems if it is not accepting the same arguments?

[Bazenga]

That makes sense yeah. Thank you, thank you, thank you.