Question

My app consolidates data from other DBs for reporting purposes. We can’t link the databases, so all the data processing has to be done in code – this is fine as we want to allow manual validation during the imports.

Certain users will be able to start an update through the Silverlight 4 front end.

I have 3 tables in database x that are fed from one EF4 Model (ModelX). I want to join those tables together, select specific columns and return the result as a new entity that exists in a different EF4 Model (ModelY). I’m using this query:

var myQuery = from i in DBx.table1 from it in DBx.table2 from h in DBx.table3 where (i.id==it.id && h.otherid == i.otherid) select new ModelYServer {Name = i.name,Thing = it.thing, Stuff = h.stuff};

The bit i’m stuck on, is how to execute that query, and wait until the Asynchronous call has completed. Normally, i’d use:

DomainContext.Load<T>(myQuery).Completed += (sender,args) =>
{List<T> myList = ((LoadOperation<T>)sender.Entities.ToList();};

but I can’t pass myQuery (an IEnumerable) into the DomainContext.Load() as that expects an EntityQuery. The dataset is very large, and is taking up to 30 seconds to return, so I definitely need to wait before continuing.

So can anyone tell me how I can wait for the IEnumerable query to complete, or suggest a better way of doing this (there very likely is one).

Thanks

Mick

Answer 1

One simple way is just to force it to evaluate by calling ToList:

var query = from i in DBx.table1
            join it in DBx.table2 on i.id equals it.id
            join h in DBx.table3 on i.otherid equals h.otherid
            select new ModelYServer {
                Name = i.name,
                Thing = it.thing,
                Stuff = h.stuff
            };
// This will block until the results have been fetched
var results = query.ToList();

// Now use results...

(I’ve changed your where clause into joins on the earlier tables, as that’s what you were effectively doing and this is more idiomatic, IMO.)