Get asynchronous data from wcf service - silverlight

Question

I have a wcf which retrieves information from a database.
I also have a Silverlight client application which references that service and uses it to retrieve the data.
public void init(ref Cluster cluster)
{
_SelectedCluster = cluster;
MyEntities svc = new MyEntities(new Uri("http://localhost:49672/MyDataService.svc/"));
docs = new DataServiceCollection<EC_Documents>();
var query = from c in svc.EC_Documents
where c.clusterID == _SelectedNode.ID
orderby c.clusterID
select c;
docs.LoadCompleted += docs_LoadCompleted;
docs.LoadAsync(query);
}
private void docs_LoadCompleted(object sender, LoadCompletedEventArgs e)
{
if (e.Error == null)
{
if (docs.Continuation != null)
{
docs.LoadNextPartialSetAsync();
}
else
{
_SelectedCluster.Value = docs.Count;
}
}
}
Because the call is asynchronous, I had to make docs a member of the class and check its count at the docs_LoadCompleted method.
I also have a _SelectedCluster which is an object of type Cluster as a member in the class,which holds the current cluster object in the iteration.
I have a problem assigning the result to the currently selected node _SelectedCluster.Value member.
Because the call is asynchronous, I cannot iterate on all my clusters objects and assign the result synchronously, If I do that, the assignment is always on the last cluster in the iteration.
Any suggestions?

Answer 1

Re-arrange your code to benefit from closures:-
public void init(Cluster cluster)
{
MyEntities svc = new MyEntities(new Uri("http://localhost:49672/MyDataService.svc/"));
var docs = new DataServiceCollection<EC_Documents>();
var query = from c in svc.EC_Documents
where c.clusterID == _SelectedNode.ID
orderby c.clusterID
select c;
docs.LoadCompleted += (s, e) =>
{
if (e.Error == null)
{
if (docs.Continuation != null)
{
docs.LoadNextPartialSetAsync();
}
else
{
cluster.Value = docs.Count;
}
}
};
docs.LoadAsync(query);
}
Now multiple calls to init can be made each using its own instance DataServiceCollection<EC_Documents>. I'm not sure what you want to do about the _SelectedNode.ID value that looks wrong to me, you ought to be passing that value in as a parameter on the init. Of course with docs now being local you will need to decide what to with it once all the docs for a cluster ID is loaded.