"I have a question about retrieving entities from cache using DevForce Silverlight.  I was wondering why you have to write an async query in order to retrieve cached entities?  I figured since the cached data is already on the client, I can just access it using client side LINQ."

Excellent question. The answer is: you can query the cache synchronously J

 

Here is a little experiment using PrismExplorer.

 

·         Launch it

·         Run the query “Get Customers with Orders in Oregon” query (this populates the cache with some customers and some orders)

·         Put breakpoint on line in “Infrastructure.Repository” class that reads:
EntityManager.DefaultQueryStrategy = QueryStrategy.Normal;
That’s line 31 in the version on my desktop.

·         Back in the UI, select “Get Orders in Cache”

·         It will break here

·         Open the Immediate Window

·         Enter “query”; you should see something like this:

query

{value(IdeaBlade.EntityModel.EntityQueryProxy`1[DomainModel.Order])}

    [IdeaBlade.EntityModel.EntityQuery<DomainModel.Order>]: {value(IdeaBlade.EntityModel.EntityQueryProxy`1[DomainModel.Order])}

    CommandTimeout: 0

    ElementType: {DomainModel.Order}

    EntityManager: {DomainModel.DomainModelEntityManager}

    QueryableType: {DomainModel.Order}

    QueryStrategy: {IdeaBlade.EntityModel.QueryStrategy}

    Tag: null

 

If you dig in, you will see that the QueryStrategy is CacheOnly

 

·         Enter “EntityManager.ExecuteQuery(query)”; you should see something like this:

Count = 28

    [0]: {DomainModel.Order}

    [1]: {DomainModel.Order}

    [2]: {DomainModel.Order}

    [3]: {DomainModel.Order}

    [4]: {DomainModel.Order}

    ...

    [25]: {DomainModel.Order}

    [26]: {DomainModel.Order}

    [27]: {DomainModel.Order}

 

Yup. The query is executing immediately and synchronously.

 

 

One common tactic is to set the EntityManager.DefaultQueryStrategy to a CacheOnly strategy. Then DevForce will attempt to satisfy all queries without an explicit strategy from the cache. You can always take a query and change its strategy by saying “q.With(QueryStrategy)” .

 

Just make sure the EntityManager can do what you ask of it.