Question

I’ve created an application that exposes a self-hosted OData web service. The web service exposes a collection of objects named “Main”. Each of these Main objects has a reference to a releated “Details” object, which is very large (many properties, nearly a hundred).

I now use LinqPad to test my web service, which seems to work fine.

Often I need information from both the “Main”-collection and the related “Details” object. This can be accomplished by running the following linq query:

 from m in Main.Expand( "Details" )
 where m.ID==57
 select m

This correspons to the url:

 "http://MachineName:port/ServiceName/Main()?$filter=ID eq 57&$expand=Details"

This query works fine and returns the full Main object and the full related Details object.

However, the Details object is very large, and often I only need the value of a single single property from both of the objects.

Manually, I can construct a url that gives me exacly that:

 "http://MachineName/ServiceName/Main()?filter=ID eq 57&$expand=Details&$select=Property1,Details/Property2"

which returns xml containing only the value of Main.Property1 and the value of the related Details.Property2.

Question: Why can’t I create a linq query that does just that?

When I try something like:

 from m in Main.Expand( "Details" )
 where m.ID == 57
 select new{ m.Property1, m.Details.Property2 }

it gives me the an error message: “NotSupportedException: Cannot create projection while there is an explicit expansion specified on the same query.”

I have now given up using Linq to construct the query. But knowing the corrct url like above, how can i use that url directly in code (C# client) and how do I then access the result?

Answer 1

Doesn’t just

from m in Main
where m.ID == 57
select new { m.Property1, m.Details.Property2 }

work for you?