How to add/edit DataServiceQuery LINQ Projections in Silverlight? - linq

Question

Silverlight 5 / WCF Data Services 5.6.0 / Entity Framework 5 / Asynchronous LINQ DataServiceQuery
How can I reset/delete/uncache/remove the projections from my DataServiceQuery LINQ query in subsequent executions ?
Consider the below code:
var query =
(
from c in context.Customers
select new Customers()
{
ID = c.ID,
Name = c.Name,
}
) as DataServiceQuery<Customers>;
query.BeginExecute((result) =>
Dispatcher.BeginInvoke(() =>
{
// process results from query...
// query.EndExecute(result).ToList();
}), null);
In the above snippet, I'm creating a LINQ query with two projections (columns) which will return the ID and Name fields via WCF Data Services. This works fine; issue starts below...
In another method which executes later, I have a similar query to fetch additional columns/projections. However, the below LINQ query returns the same resultset as above and ignores the additional columns:
var query =
(
from c in context.Customers
select new Customers()
{
ID = c.ID,
Name = c.Name,
Age = c.Age, // additional columns returning null
Height = c.Height // additional columns returning null
}
) as DataServiceQuery<Customers>;
query.BeginExecute((result) =>
Dispatcher.BeginInvoke(() =>
{
// process results from query...
// query.EndExecute(result).ToList();
}), null);
Removing all projections to return all columns fails too; I just get back the initial ID and Name fields specified earlier:
var query =
(
// No projections, just get ALL columns please!
from c in context.Customers
select c
) as DataServiceQuery<Customers>;
query.BeginExecute((result) =>
Dispatcher.BeginInvoke(() =>
{
// process results from query...
// query.EndExecute(result).ToList();
}), null);
How can I get the DataServiceQuery object to discard the previously specified projections? I don't have the option to execute the query which returns all columns first.

Answer 1

Issue resolved: Before executing any LINQ query, set the below MergeOption on the WCF Data Service context:
context.MergeOption = MergeOption.OverwriteChanges;
Related info:
http://social.msdn.microsoft.com/Forums/silverlight/en-US/f36d2643-661e-4048-88cf-a38df36a0b1a/linq-expand-and-dataservicequery
WCF Data Service and Silverlight: DataServiceQuery<T> will not re-perform query