C# 4 and .NET 4

Using WCf Data services with the aDo.neT entity framework ❘ 895
Now, use the Data Service template and create RestaurantDataService.svc . The .svc fi le contains the
ASP.NET ServiceHost directive and uses the DataServiceHostFactory to instantiate the data service on
request.
< %@ ServiceHost Language="C#" Factory="System.Data.Services.DataServiceHostFactory,
System.Data.Services, Version=4.0.0.0, Culture=neutral,
PublicKeyToken=b77a5c561934e089"
Service="Wrox.ProCSharp.DataServices.RestaurantDataService" % >
code snippet RestaurantDataServiceWeb/RestaurantDataService.svc
With the code - behind, you need to change the template parameter of the DataService < T > class to reference
the previously created entity data service context class, and change the entity set access rule and service
operations access rule to allow access:
using System.Data.Services;
using System.Data.Services.Common;
namespace Wrox.ProCSharp.DataServices
{
public class RestaurantDataService : DataService < RestaurantEntities >
{
// This method is called only once to initialize service - wide policies.
public static void InitializeService(DataServiceConfiguration config)
{
config.SetEntitySetAccessRule(“Menus”, EntitySetRights.All);
config.SetEntitySetAccessRule(“Categories”, EntitySetRights.All);
}
}
}
config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2;
code snippet RestaurantDataServiceWeb/RestaurantDataService.svc.cs
Now, you can use a web browser to invoke queries as before to this data service; for example, you can use
http://localhost:13617/RestaurantDataService.svc/Menus to receive the AtomPub of all menus
from the database. Next, you create a client application that makes use of the client part of Data Services.
With a large database you shouldn’t return all the items with a query. Of course, the
client can restrict the query to just request a certain limit of items. However, can you
trust the client With confi guration options you can restrict limits on the server. For
example, by setting config.MaxResultsPerCollection you can restrict the number
of items that are returned from a collection to a maximum. You can also confi gure the
maximum batch count, the maximum number of objects on an insert, and the maximum
depth of objects in the tree. As an alternative, to allow any query you can also
defi ne service operations as was shown in the section “Additional Service Operations.”
.neT applications using system.data.service.Client
Earlier in this chapter, you read how a .NET client application can be created that simply sends HTTP
requests by using the HttpWebRequest class. The client part of Data Services, with the namespace
System.Data.Services.Client , offers functionality for the client to build HTTP requests. The two most
important classes with this namespace are DataServiceContext and DataServiceQuery < TElement > .
DataServiceContext represents the state that is managed on the client. This state keeps track of objects
that are loaded from the server as well as all the changes made on the client. DataServiceQuery < TElement >
represents an HTTP query to a data service.
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