private void InitializePagedView() {
// Let's look at all customers. The query can be of any complexity, but must be an EntityQuery<T>.
// If the query contains an OrderBy, that sort order will always be primary and any sort columns
// selected by the user in the grid will be added as "ThenBy" clauses when sorting the results.
// Don't execute the query (unless you do want the view to work with CacheOnly paging queries).
// The EntityQueryPagedCollectionView (PCV) will execute paged queries, first DataSourceOnly to load
// the page, and then using the QueryStrategy in effect for the query or EM.
// We haven't logged in with this EntityManager, so the PCV will do an implicit login with null
// credentials before executing the query. If you require real login credentials, then you should
// be sure to login the EM first.
// We're deferring the load here to add a SortDescription (instead of an OrderBy on the query).
// Once the SortDescription is set we can load the view.
var query = _entityManager.Customers;
View = new EntityQueryPagedCollectionView(
query, // Source of data
PageSize, // Page size
PageSize, // Load size - no lookahead caching here
true, // Whether to defer the load
false); // Whether to add primary key to sort columns
// Listen for errors now - we can catch connection/login errors when refresh occurs.
View.PageLoadError += pcv_PageLoadError;
// Set a sort column here - user choices in grid will override.
View.SortDescriptions.Add(new SortDescription("CompanyName", ListSortDirection.Ascending));
View.Refresh();
// Listen for a few events.
View.PageChanging += PageChanging;
View.CurrentChanged += CurrentItemChanged;
}
private void LoadView() {
// Create and start loading the PCV.
// Neither EQPCV nor PCV will work with anonymous types.
if (AnonymousFns.IsAnonymousType(Query.ElementType)) {
throw new NotSupportedException("Anonymous types are not currently supported. To work around this limitation, you can instead project into a custom type.");
}
if (IsEntityQuery) {
EntityManager.GetEntityGroup(Query.ElementType).EntityChanged += ObjectDataSource_EntityChanged;
}
IsLoadingData = true;
HasChanges = false;
// Convert from our "descriptors" to the "descriptions" known by a PCV.
var sortFields = new SortDescriptionCollection();
SortDescriptors.ForEach(s => sortFields.Add(s.ToSortDescription()));
var groupFields = new ObservableCollection<GroupDescription>();
GroupDescriptors.ForEach(g => groupFields.Add(g.ToGroupDescription()));
// We'll use an EQPCV or PCV depending on a few factors: 1) an EntityQuery (so we can issue skip/take, 2) paging
bool useEqpcv = Query is EntityQuery && PageSize > 0;
if (useEqpcv) {
EntityQueryPagedCollectionView pcv = null;
var query = Query as EntityQuery;
var filter = GetQueryFilter();
if (sortFields.Count > 0 || groupFields.Count > 0) {
pcv = new EntityQueryPagedCollectionView(query, PageSize, LoadSize, sortFields, groupFields, filter);
} else {
pcv = new EntityQueryPagedCollectionView(query, PageSize, LoadSize, true, true);
pcv.SetQueryFilter(filter);
pcv.Refresh();
}
Data = pcv;
DataView = pcv;
} else {
// Use the standard PagedCollectionView (when paging isn't wanted or not an EntityQuery)
IEntityQuery query = Query;
if (Query is EntityQuery) {
query = GetFilteredQuery();
}
EntityManager.ExecuteQueryAsync(query, args => {
PagedCollectionView pcv = new PagedCollectionView(args.Results);
sortFields.ForEach(d => pcv.SortDescriptions.Add(d));
groupFields.ForEach(d => pcv.GroupDescriptions.Add(d));
pcv.PageSize = PageSize;
Data = pcv;
DataView = pcv;
});
}
}