Performing Child Data Retrieval using Intersoft DataSource™

Hello,

I promised several of our respondents to have a sample that demonstrate capability to retrieve child collection from parent object using Intersoft Data Source™. So I’ll try to elaborate it in this post in detail with step by step approach.

• Sign up and download the Intersoft Data Source™ CTP release from here.
• Follow the steps to create Astoria (ADO.NET Data Service) connection and set the service reference to your Silverlight Application Project. (Here is the link)
• Don’t forget to add reference to ISNet.Silverlight, ISNet.SIlverlight.DataSource and System.Windows.Controls.Data.
• Lets start by creating the UI first.

In this sample I’m going to use three data grids to show Customers – Orders – Orders Details relationship. So the first Grid will show the list of Customers, the second Grid will show the Orders from selected customer in the Customers Data Grid, and the third Grid will show the Order Details from selected order in Orders Data Grid.

• Insert the Astoria Data Source and configure its settings.

• Since I want my grid to retrieve the child data when ever i select a row in the grid, I’m going to hook the SelectionChanged event in Customers Grid and Orders Grid

• Next we need to attached Selecting and Selected Event Handler in Astoria Data Source, so that we can control the data retrieval process later on.

• Everything is set, and now lets go to the code behind.
• First of all we want the Application to load the data directly when application is loaded, therefore we need to call AstoriaDataSource1.Select(“Customers”) when the application is ready.

• Remember that we attached SelectionChanged event for Customers Grid and Orders Grid? Lets put some action into it.
  So we will retrieve Orders when an item in Customers Grid is selected, and we will retrieve Orders Details when an item in Orders Grid is selected.

• Now is the important part. When we call AstoriaDataSource1.Select(“Orders”) in CustomersGrid_SelectionChanged, we want it only to retrieve the Orders from selected item (Customer with specific CustomerID). So how can we handle this?
  Currently you need to handle it at Astoria Data Source’s Selecting Event Handler as follows.

When you call AstoriaDataSource1.Select(“Orders”), it will asked the AstoriaDataSource to perform data retrieval process. You can interupt the process at two points which are at the beginning (Selecting) and at the ending (Selected). Since we want the AstoriaDataSource to select only Orders of current selected Customer, we need to provide advance query during Selecting event.

Customers customer = CustomersGrid.SelectedItem as Customers;

var query = from c in context.CreateQuery<Customers>(“Customers”).Expand(“Orders”)
where c.CustomerID == customer.CustomerID
select c;

DataServiceQuery<Customers> serviceQuery = query as DataServiceQuery<Customers>;
e.DataServiceQuery = serviceQuery;

By providing e.DataServiceQuery with an advanced query like this, the Astoria Data Source will compile it and send it to Astoria Data Service.

• Lastly what you need to do is to handle the action when the data is retrieved at the Selected Event.

Since Astoria sends the data back as collection of EntityDescriptor, we need to do additional Linq query to get the object collection correctly.

In the query i also put additional checking c.Entity.GetType() == typeof(Orders) is to filter out parent data when we’re doing child data retrieval.

• And we’re done. Run your application and you’ll get something like this.

Regards
Andry

Sample Link