R – GridView sorting doesn’t work when I Enable Caching in Custome Paging and sorting

It's possible that after the postback occurs the datasource is not being maintained or refilled and there are no items to populate the grid. Are you handling state correctly for the datasource object (rebinding/keeping the source alive) when paging is enabled?

This may sound like a vague answer, but without an example of how the source is getting the data it's kind of hard to diagnose why the items would be gone.

Edit:
The method I was thinking of was for callback paging/sorting. However I did find some info ont he ODS & Paging.. make sure you have set the following:

1. GridView: AllowPaging and off course you need to set PageSize.
2. ObjectDataSource: EnablePaging, also you need to set the:
   • MaximumRowsParameterName="maxRows"
   • StartRowIndexParameterName="startRowIndex"
   • SelectCountMethod="RecordCount"

I think you only need to set the 3 sub items of item 2 if you want to handle paging size etc manually.

Then you can read more up on this here.

Okay I figured it out. Here is the solution :

1. Tie the BLL to an ObjectDataSource.
2. Provide overloaded methods for the select method in your BLL, to support paging and sorting.
3. Provide the SortParameterName in the ObjectDataSource. This is the the name of the string input parameter of your select method in your BLL.

For more information see : http://msdn.microsoft.com/en-us/library/aa479347.aspx

Here's an example, this is just a quck example for demo I did not support sort direction, or optimized the code etc:

namespace CodeSamples.DAL
{
    public static class DAL
    {
        public static CustomerList GetCustomerList(string SortExpression)
        {
            return GetCustomerList(int.MaxValue, 0, SortExpression);
        }

        public static CustomerList GetCustomerList()
        {
            return GetCustomerList(int.MaxValue, 0,String.Empty);
        }

        public static CustomerList GetCustomerList(int maximumRows, int startRowIndex, string SortExpression)
        {
            const string query = "Select * from Customers";
            CustomerList customers = new CustomerList();


            SqlConnection conn = new SqlConnection("Data Source=Win2k8;Initial Catalog=NorthWind;User ID=sa;Password=XXXXX");
            SqlCommand command = new SqlCommand(query, conn);
            conn.Open();
            SqlDataReader reader = command.ExecuteReader();

            ArrayList rows = new ArrayList();

            while (reader.Read())
            {
                object[] values = new object[reader.FieldCount];
                reader.GetValues(values);
                rows.Add(values);
            }

            conn.Close();

            int currentIndex = 0;
            int itemsRead = 0;
            int totalRecords = rows.Count;

            foreach (object[] row in rows)
            {
                if (currentIndex >= startRowIndex && itemsRead <= maximumRows)
                {
                    customers.Add(new Customer { Name = row[1].ToString(), ID = row[0].ToString(), ContactName = row[2].ToString() });
                    itemsRead++;
                }
                currentIndex++;
            }


        CustomerList sortedCustomers = new CustomerList();

        string sortBy = SortExpression;
        bool isDescending = false;

        if (SortExpression.ToLowerInvariant().EndsWith(" desc"))
        {
            sortBy = SortExpression.Substring(0, SortExpression.Length - 5);
            isDescending = true;
        }         

        var sortedList = from customer in customers
                         select customer;

        switch (sortBy)
        {
            case "ID":
                sortedList = isDescending ? sortedList.OrderByDescending(cust => cust.ID) : sortedList.OrderBy(cust => cust.ID);
                break;

            case "Name":
                sortedList = isDescending ? sortedList.OrderByDescending(cust => cust.Name) : sortedList.OrderBy(cust => cust.Name);
                break;

            case "ContactName":
                sortedList = isDescending ? sortedList.OrderByDescending(cust => cust.ContactName) : sortedList.OrderBy(cust => cust.ContactName);
                break;

        }

        foreach (Customer x in sortedList)
        {
            sortedCustomers.Add(x);
        }    

            return sortedCustomers;
        }
    }  

    public class CustomerList : List<Customer>
    {

    } 

    public class Customer
    {
        public Customer()
        {
        }

        public Customer(string Name, string id)
        {
            this.Name = Name;
            ID = id;
        }
        public string ID
        {
            get;
            set;
        }

        public string Name
        {
            get;
            set;
        }

        public string ContactName
        {
            get;
            set;
        }


    }
}

In the ASPX page :

  <asp:GridView ID="GridView1" runat="server" AllowPaging="True" 
            AutoGenerateColumns="False" DataSourceID="ObjectDataSource1" 
            AllowSorting="True">
            <Columns>
                <asp:BoundField DataField="ID" HeaderText="ID" SortExpression="ID" />
                <asp:BoundField DataField="Name" HeaderText="Name" SortExpression="Name" />
                <asp:BoundField DataField="ContactName" HeaderText="ContactName" SortExpression="ContactName" />
            </Columns>
        </asp:GridView>
        <asp:ObjectDataSource ID="ObjectDataSource1" runat="server" 
            SelectMethod="GetCustomerList" SortParameterName="SortExpression"
            TypeName="CodeSamples.DAL.DAL">
        </asp:ObjectDataSource>

For more information see : http://msdn.microsoft.com/en-us/library/aa479347.aspx