Can you Query me now?
(Silverlight, WCF, Webservices, and Mobile)
EntitySpaces 2009 Q2 is going to revolutionize your ability to use the EntitySpaces 2009 architecture on the client side of any two-way conversation, whether it be a Silverlight, WCF, or a webservices conversation. In fact, you will be able to work on the client side as if the full EntitySpaces architecture was at your disposal but without actually requiring the EntitySpaces architecture be present on the client. "But how can that be?" you wonder. Continue reading and we will explain.
EntitySpaces has always had good support for mobile applications via our Compact Framework support. We even generate "smarter" proxies than the ones generated by Visual Studio for WCF or webservices scenarios. Our proxies maintain row state such as (inserted, updated, and deleted) such that all that is required is that you send the data back to the server and commit it. But this client side proxy support is about to become much, much more powerful and can be used for non-mobile scenarios such as Silverlight, WCF, and webservices. With our enhanced proxies (especially for mobile applications where space is limited) this can prove to be a very powerful way to use EntitySpaces. We like to think of this as a sort of "Virtual EntitySpaces Mode" as it feels just like EntitySpaces only it really doesn't require the full architecture on the client side. So, let's dive into this and see how it works starting with a review of our current proxy support.
Our Current Client Side Proxy Functionality
The EntitySpaces Client Side proxies offer the ability to easily work with EntitySpaces on the client side of a two way conversation without requiring any of the EntitySpaces assemblies. Our proxies also track the dirty state for you so that when you send data back to the server EntitySpaces automatically knows whether to insert, update, or delete the data. This functionality is already built into the currently shipping ES2009 Q1 release. The template that you use to create the Client Side proxies is highlighted below.
When you execute the "Client Side Proxy/Stub" template there are currently two classes generated for you, the Collection and Entity class. Shown below are the proxy stub classes that were generated by the "Client Side Proxy/Stub" template for the Microsoft Northwind Suppliers table. Notice that the classes do not inherit from any base classes nor do they require any of the EntitySpaces assemblies. Also, in the SuppliersProxyStub (entity) class notice the esRowState property. This is the property that EntitySpaces uses to determine the state of the entity (inserted, updated, or deleted) and the proxy is smart enough to set this property for you based on the actions you take (you do not have to worry about setting it). These two classes are extremely small and lightweight in size.
With these two classes you work with data on the client side of a conversation without EntitySpaces being present, but something is missing, a feature that hooks most EntitySpaces developer once they start using it.
New Functionality Coming in ES2009 Q2
In our ES2009 Q2 release the Client Side template will now generate a new, optional, third class, the "QueryProxyStub" class. Yes, you guessed it, the full EntitySpaces DynamicQuery API now available on the client side of a two-way conversation. Take a look at the SuppliesQueryProxyStub class below. This class is just like the DynamicQuery classes you are accustomed to using already only it inherits from a new class named esDynamicQuerySerializable. If you take a close look at the methods in the esDynamicQuerySerializable class you will notice that there are no methods to load or execute the query itself (more on this later). This query can only be created, defined, and then serialized back to the server (a very cool way to write a Silverlight application). If you have never seen how powerful our DynamicQuery API is check out our Showcase post HERE.
Now, imagine that you're on the client side of a WCF conversation or even running down inside the browser in a Silverlight application and you need to query your Supplier table for data. No problem, here is how you would accomplish that task with the new proxy query class.
SuppliersQueryProxyStub sQuery = new SuppliersQueryProxyStub ();
sQuery.Select(sQuery.SupplierID, sQuery.Region);
sQuery.Where(sQuery.Country == "Spain");
Notice that we do not call sQuery.Load(). This is because the esDynamicQuerySerializable has no way to actually load data, it represents the query only, the ability to load it (or execute it) exists on the server side of the conversation. Also, the full join syntax is available although it is not shown above in the query. The proxy queries are fully serializable which is the key to how it works. At a very high level this is how you would fetch data from the server, imagine a method like this:
public SuppliersCollectionProxyStub FetchSupplers(SuppliersQueryProxyStub query)
You would transmit the proxy stub query to the server, where it will be deserialized, assigned to a full server query object, executed, and then the resulting proxy stub collection would be returned. The code will look very much like this.
public SuppliersCollectionProxyStub FetchSupplers(SuppliersQueryProxyStub query)
{
SuppliersCollection coll = new SuppliersCollection();
coll.Query = query as esDynamicQuerySerializable;
coll.Query.Load();
// more code below ...
}
Notice how we are able to merely assign our SuppliersQueryProxyStub object to the full blown SuppliersCollection's query object and then execute it. Could it be any easier?
EntitiySpaces.DynamicQuery - A New Assembly
Just where does this esDynamicQuerySerializable class that our SuppliersQueryProxyStub inhertis from live? The answer is a new assembly that will ship with ES2009 Q2 named EntitySpaces.DynamicQuery.dll. This is very tiny (less that 50k) assembly that only references System.Core and System.XML and is fully Silverlight 2.0 compliant. It does not link with EntitySpaces.Core or EntitySpaces.Interfaces. However, even better we are not maintaining two separate DynamicQuery API's. This new assembly and class is used on the server side as well, which means this new assembly is required now for EntitySpaces applications. Look at the diagram below which shows the hierarchy of a normal DynamicQuery class as generated by the ES2009 Q2 Generated Master template. This preserves your current API.
Notice the the original base class esDynamicQuery is still there, however, it now inherits from the esDynamicQuerySerializable class. In order to run under Silverlight our client side DynamicQuery assembly could not reference the System.Data namespace, so we have separated the original esDynamicQuery into the two classes you see above.
What Does it All Mean?
Our new enhanced client side proxies will allow you to have a "Virtual EntitySpaces Architecture" running almost anywhere including mobile devices, Silverlight applications, WCF scenarios, and webservices. It will act and feel just like EntitySpaces Of course, we can already run in all of these environments but with ES2009 Q2 and the addition of the DynamicQuery proxy and the massive DynamicQuery API enhancements that are also coming you will truly be blown away by the productivity and reach of the EntitySpaces Architecture. The only thing that is required on the client to make this all possible is the tiny EntitySpaces.DynamicQuery assembly (less than 50k) which is completely Silverlight compliant. There are other enhancements that will be made to the proxies but we will keep them small and lightweight.
There are also a few technical issues we must solve yet, though most have been worked out. For example, where do the extra properties go when you bring them back via a join? In the full server side classes this is handled gracefully, and we make those properties appear as if there are in your strongly typed entities via sophisticated binding support. How do we do this on the client side? These are a few of the issues we must solve yet.
We find this new support terribly exciting and it presents almost boundless usage scenarios. Especially when you factor in the enhancements we are making to DynamicQuery API itself, but that is the topic for another post. And keep those comments coming in our ES2009 Wish List forum, we are listening and will implement a lot of your requested features.
From Mobile Devices to large scale enterprise solutions in need of serious transaction support, EntitySpaces can meet your needs. Whether you’re writing an ASP.NET application with Medium Trust requirements, a Mono application, or a Windows.Forms application, the EntitySpaces architecture is there for you. EntitySpaces is provider independent, which means that you can run the same binary code against any of the supported databases. EntitySpaces is available in both C# and VB.NET. EntitySpaces uses no reflection, no XML files, and sports a tiny foot print of less than 200k. Pound for pound, EntitySpaces is one tough, dependable .NET architecture.
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Persistence Layer and Business Objects for Microsoft .NET
http://www.entityspaces.net