Batch queries for DomainContext with RIA services

Question

I have a simple Silverlight web page that is displaying dtaa from a remote database using RIA services. I have a DomainContext in which I make queries on the database through.

context.Load(context.GetSitesQuery()).Completed += new EventHandler(Query_Completed);

Notice that I am listening for the query to finish. The problem here is that I need to make at least 20 different queries, with each query involving a different entity object. The application really can't do much until all the data is loaded either. So, I would really only like to know when all the queries are finished. Is there an easy way to create a batch of queries?

I tried this on my own, but I ran into a problem due to the fact that each query involves a different entity. I created a list of EntityQuery<Entity> and figured I could iterate over it and execute all the queries, but the Load method either complains about having the wrong parameters or it fails during runtime.

Answer 1

We have accomplished what you are meaning to do by tracking the number of pending load operations. When it reaches 0, you are effectively done.

using System.ServiceModel.DomainServices.Client;

...

private int _loadCounter;
private TheDomainContext _domainContext;

private void Load<TEntity>(EntityQuery<TEntity> query,
                           Action<LoadOperation<TEntity>> callback)
                       where TEntity : Entity
{
    BeginLoading();
    Action<LoadOperation<TEntity>> internalCallback = 
            loadOp => {
                          callback(loadOP);
                          EndLoading();
                      };
    _domainContext.Load(query, internalCallback , null);
}

private void BeginLoading()
{
    _loadCounter++;
    // You could add logic to indicate the app is busy
}

private void EndLoading()
{
    _loadCounter--;
    if (_loadCounter == 0)
    {
        OnLoadComplete();
    }
}

private void OnLoadComplete()
{
    // TODO Everything is loaded
}

private void BeginLoadingTheQueries()
{
    // Increment once here to prevent the OnLoadComplete from occurring
    // before all queries have started
    BeginLoading();
    Load(_domainContext.GetSitesQuery(), Query_Completed);
    Load(_domainContext.GetOtherQuery(), OtherQuery_Completed);
    EndLoading();
}