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This article mainly explains "ADO. NET data service is what". The explanation content in this article is simple and clear, easy to learn and understand. Please follow the idea of Xiaobian slowly and deeply to study and learn "ADO. NET data service is what" together!

The ADO. NET Data Services Framework supports functionality beyond representational state transfer (REST) semantics. For example, service operations and listeners can be used to add validation logic or security procedures to queries and updates. Service operations can be written using the standard syntax defined by ADO. NET data services to filter or sort the output. The above example query string uses sort syntax, where the $orderby and $top operators are applied to the operation result.

Listeners allow you to insert custom application logic into the request or response process of a data service. Listener methods must be explicitly registered for a given set of entities exposed by the data service. When a query, insert, update, or delete operation is performed on the specified entity set, the appropriate listener is invoked. The listener may then change the data, enforce authorization policies, or even terminate the operation.

ADO. NET data services also support stored procedures implemented by relational database management systems. The entity data model supports mapping data retrieval and modification to stored procedures. ADO. NET Data Services has adapted this functionality. Service scope visibility for service operations is controlled in much the same way as entity set visibility. For example, to make the CustomersByCity method in the example above accessible, add the code in the following figure to a class derived from DataService.

public class Northwind : DataService { public static void InitializeService( IDataServiceConfiguration config) { config.SetServiceOperationAccessRule("CustomersByCity", ServiceOperationRights.All); } [WebGet] public IQueryable CustomersByCity(string city) {… } }

listener

With ADO. NET data services, data service developers can intercept the request/response pipeline and inject custom validation logic. In ADO. NET data services, listeners serve two main purposes: enabling you to add authentication logic to the processing pipeline; and providing a place to insert custom authentication policies into each request. Query listeners cannot take arguments.

Request/URI Handling

When the data service receives a GET request, it processes the request URI and invokes any query interception methods defined on the data service. The following example demonstrates an implementation of the query listener method, which intercepts GET requests for orders. This listener returns only orders assigned to customers who meet the CustomerID=="AROUT" condition. More code is required to authenticate the user who sent the request so that this method will return an order assigned to each user.

[QueryInterceptor("Orders")]

public Expression FilterOrdersByCustomer()

{

return o => o.Customers.CustomerID == "AROUT";

}

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