Behind The Scene: Astoria Data Source Control

Hi

Probably some of you are confused with the declarative configuration that you need to set up when you want to use Astoria Data Source control from Intersoft DataSource™. In this post I’ll try to elaborate the things one by one so hopefully its easier to understand how the Astoria Data Source control works.

First of all let me show you one way to select data from Astoria Data Service manually. I assumed you already know how to establish Astoria Data Service, or you can always learn it from my earlier post, or from MSDN references.

As you can see we need to do lots of things, creating the service proxy / object, create the query, call the asynchronous call. Then attached the asynchronous call back where we can grab the data then apply it to our UI control. Furthermore we’re going to need similar process for Create, Update and Delete operation which might take some time to manage it properly.

Here where Astoria Data Source tries to help, it tries to simply the CRUD operation to ADO.NET Data Service. Please see the note i put in the picture above. Those are the information we need for Astoria Data Source declarative configuration.

The Reference Namespace was defined when you set the service reference in your silverlight project.

The Service TypeName is your ADO.NET Data Service’s Object Context where you define in your MyNorthwind.svc.cs file.

The Service Host is basically the host that contains the ADO.NET Data Service file, while the Service Target is the actual ADO.NET Data Service file. Later when you deploy the project, you need to adjust the Service Host accordingly to where you host your application.

The Data Object TypeName is object type that available in your ADO.NET Data Service, in this case i used Northwind Database therefore I’ll have Customers, Products, Employees, etc as my Data Object TypeName.

Here is what its how the declarative configuration looks like:

Given this info, its enough for us to help you perform CRUD operation in more elegant way. One thing you should note that you can also specified the configuration individually per AstoriaDataService, something like:

In this configuration, the AstoriaDataService[Customers] will look to http://localhost:52026/MyNorthwind1.svc instead of http://localhost:52025/MyNorthwind.svc. So if you have multiple services you don’t need to create additional data source control and configure other integrated features, you just need to set this individual settings to each data service and you’re set.

To do Data Binding with this Astoria Data Source: Data Binding to Silverlight Data Bound Control using Intersoft Data Source(tm)

To do CRUD operation using Astoria Data Source: Performing CRUD to Silverlight Data Grid using Intersoft Data Source ™

To do Child Data Retrieval using Astoria Data Source: Performing Child Data Retrieval using Intersoft DataSource™

Next I want to show you event handlers that Astoria Data Source has, and what you can do at each event.

• Object Creating Event
  This is called when Service Object is going to be created.
  

–> at this point
proxy = new MySilverlightApplication.MyServiceReference.NorthwindEntities(new Uri(“http://localhost:52025/MyNorthwind.svc”));

• Object Created Event
  This event is called when Service Object has been created.

proxy = new MySilverlightApplication.MyServiceReference.NorthwindEntities(new Uri(“http://localhost:52025/MyNorthwind.svc”));
–> at this point

You can grab the Service Object from the event argument, and probably change some property inside it if necessary.

• Object Disposing Event
  This event is called when the Service Object is going to be disposed.
  Again we passed the Service Object here, just in case you need to do additional clear up before the Service Object is disposed.
• Selecting Event
  This event is called before we perform asynchronous call to perform data selection. You can add / change additional select argument or supply your own query like what i did in Performing Child Data Retrieval using Intersoft DataSource™ .

–> at this point
serviceQuery.BeginExecute(new AsyncCallback(GetCustomersCompleted), serviceQuery);

• Selected Event
  This event is called when the asynchronous call is finished, and the data has been retrieved.private void

GetCustomersCompleted(IAsyncResult result)
{–> at this point

In this event you can grab the data using args.ReturnValue, and probably perform additional sub query as necessary before returning it to the UI. You can also check for Exception if the ADO.NET Data Service returns an exception from args.Exception.

• Inserting Event
  This event is called before the inserting process is executed, you can grab the actual object that going to be inserted at e.NewObjectInstance where you might want to change things if necessary.
• Inserted Event
  This event is called after the inserting process is executed, you can grab the Exception as usual if the ADO.NET Data Service returns an exception from args.Exception. You can also grab the return object from ADO.NET Data Service using args.ReturnValue.
• Updating Event
  This event is called before the updating process is executed, you can grab the actual object that going to be updated at e.NewObjectInstance where you might want to change things if necessary. If you supply the original object (for Concurrency checking purpose) you can grab the object using e.OldObjectInstance.
• Updated Event
  This event is called after the updating process is executed, you can grab the Exception as usual if the ADO.NET Data Service returns an exception from args.Exception. You can also grab the return object from ADO.NET Data Service using args.ReturnValue.
• Deleting Event
  This event is called before the deleting process is executed, you can grab the actual object that going to be deleted at e.OldObjectInstancewhere you might want to change things if necessary.
• Deleted Event
  This event is called after the deleting process is executed, you can grab the Exception as usual if the ADO.NET Data Service returns an exception from args.Exception. You can also grab the return object from ADO.NET Data Service using args.ReturnValue.

In all of this event you have e.ServiceName to distinguish operation between AstoriaDataService, so you can target the action accordingly per service.

Thats all for now.
Hope this clear things about how Astoria Data Source control works.

Regards
Andry