Silverlight paging webservice results - web-services

Question

We have a Silverlight application that calls a web service to retrieve database rows from SQL Server. These are then displayed on the screen in a paged control. However, the entire table is needed and it consists of several thousand rows. On the customer system, if we ask for more than around 1500 rows, we get HttpRequestTimedOutWithoutDetail. On our development system we need about 500,000 rows before this happens.
Obviously, what we should be doing is paging the results and returning them to the silverlight bit by bit. But I don't know how to do this. Can anyone advise, or point me to some web-pages that clearly explain the principles and methods (I am a bit simple!)
Here is the code in the Web Service:
public IQueryable<Referral> GetReferrals()
{
/*
* In the customer's environments it seems that any more than around 1500 referrals will break the system: they will fail to load.
* In the dev environment is takes around 500,000 so it seems to be timeout related.
*
* The code below was an attempt to restrict the number, only returning referrals above a certain size and within a certain age.
* It seems the customer is more interested in the smaller referrals though since they are more likely to be added to existing
* substations so if this method is re-instated, we should be using '<' instead of '>'
*
int mdToBeMet = int.Parse(ConfigurationManager.AppSettings["ReferralMDToBeMet"]);
DateTime minusNYears = DateTime.Today.AddYears(int.Parse(ConfigurationManager.AppSettings["ReferralTargetDate"]) * -1);
int maxReferralsCount = int.Parse(ConfigurationManager.AppSettings["ReferralMaxRecordCount"]);
if (mdToBeMet != 0 && maxReferralsCount != 0)
{
return this.ObjectContext.Referrals.Where(x => x.MD_to_be_Met > mdToBeMet && x.Target_Date > minusNYears).OrderByDescending(y => y.Target_Date).Take(maxReferralsCount);
}
*/
/*
* This is the 2nd attempt: the customer is mainly interested in referrals that have an allocated substation
*/
bool allocatedReferralsOnly = bool.Parse(ConfigurationManager.AppSettings["ReferralAllocatedOnly"]);
int maxReferralsCount = int.Parse(ConfigurationManager.AppSettings["ReferralMaxRecordCount"]);
if (allocatedReferralsOnly)
{
var referrals = this.ObjectContext.Referrals.Where(x => x.Sub_no != "").OrderByDescending(y => y.Target_Date).Take(maxReferralsCount);
return referrals;
}
else
{
/*
* Ideally, we should just page the referrals here and return to retrieving all of them, bit by bit.
*/
var referrals = this.ObjectContext.Referrals;
return referrals;
}
}
Many thanks for any suggestions.

Answer 1

An example to expand on the comment I gave ...
/// <summary>
/// Returns a page of Referrels
/// pageNumber is 0-index based
/// </summary>
public IQueryable<Referrel> GetReferrals(int pageNumber)
{
var pageSize = 100;
return ObjectContext.Referrals.Skip(pageNumber*pageSize).Take(pageSize);
}
Obviously you could pass in the pageSize too if you wanted, or define it as a constant somewhere outside of this method.