Question

OK, so I understand how to use the ASP.net GridView control’s paging. You set various methods to allow the control to get a subset of the data, and the number of records matched in total. Here’s my initialization code at the moment:

ObjectDataSource dataSource = new ObjectDataSource();
dataSource.EnablePaging = true;
dataSource.SelectParameters.Add(new Parameter("customerId", TypeCode.Int32, customerId.ToString()));
dataSource.SelectMethod = "SelectSomeRecords";
dataSource.StartRowIndexParameterName = "startRowIndex";
dataSource.MaximumRowsParameterName = "maximumRows";
dataSource.SelectCountMethod = "SelectAllRecordsCount";
dataSource.TypeName = "Name.Of.Data.Class";

grdUserList.DataSource = dataSource;
grdUserList.DataBind();

This works in that it passes the customer ID I’m displaying users for, as well as start row index and maximum rows, to my data class. But one thing puzzles me. Why does the control want a separate method for SelectCountMethod? At the database layer, I have a stored proc that returns the total number of matched rows as an output parameter as well as the subset requested. It would be a LOT easier if the DataGrid simply allowed my SelectMethod to return an int, indicating the total number of records matched before startRowIndex and maximumRows are applied.

This MSDN page seems to suggest (in its examples) that one should store the number of records in HttpRuntime.Cache, with an expiration time of 5 minutes. This seems to me like a far-from-perfect solution. You have potentially 5-minute-old data which may well have changed, when you could just be getting back the total number of records matched at the same time you call the SelectMethod! You’re going to want that information at the same time as you’re rendering the paged control, anyway.

My questions are, is there any way to get GridView to get its ‘all records count’ figure at the same time as it calls the ‘select method’, either through a return value or an out param? If not, how would you suggest working around this strange requirement for there being 2 methods for these 2 pieces of data, given that I will be getting my ‘all records count’ figure when I call SelectMethod? At the moment, I’m leaning towards storing that value in Session, setting it in SelectMethod, and just returning it in SelectCountMethod.

Answer 1

Just to update, what I ended up doing was writing my own paging class and just providing one page of information to the GridView at a time. I found its built-in paging mechanism to be badly implemented. The additional benefit of using your own paging class is that you can use it with other ASP.net controls that don’t have built-in paging, like the Repeater.