Shulou(Shulou.com)06/02 Report--

This article is about how to use the DataRelation object in ADO.NET. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

The ADO.NET data services framework supports functions beyond the semantics of representational state transfer (REST). For example, service operations and listeners can be used to add validation logic or security procedures to queries and updates.

You can use the standard syntax defined by the ADO.NET data service to write service operations to filter or sort the output. The sorting syntax is used in the query string in the above example, where the $orderby and $top operators are applied to the result of the operation. 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 set of entities, the appropriate listener is called. The listener may then change the data, enforce the authorization policy, or even terminate the operation.

In a DataSet that contains multiple DataTable objects, you can use the ADO.NET DataRelation object to correlate one table to another, to navigate between multiple tables, and to return child or parent rows from related tables. The parameters required to create an ADO.NET DataRelation are the name of the ADO.NET DataRelation you created and an array of one or more DataColumn references to those columns that serve as parent and child columns in the relationship. After you create an ADO.NET DataRelation, you can use it to navigate and retrieve values between multiple tables.

By default, adding an ADO.NET ADO.NET DataRelation to a DataSet adds a UniqueConstraint to the parent table and a ForeignKeyConstraint to the child table. The following code example uses two DataTable objects in DataSet to create an ADO.NET DataRelation. Each DataTable contains a column named CustID, which serves as a link between two DataTable objects. This example adds a single ADO.NET DataRelation to the Relations collection of DataSet. The * * parameters in this example specify the name of the ADO.NET DataRelation created. The second parameter sets the parent DataColumn, and the third parameter sets the child DataColumn.

Visual Basic

CustomerOrders.Relations.Add ("CustOrders", _ customerOrders.Tables ("Customers"). Columns ("CustID"), _ customerOrders.Tables ("Orders"). Columns ("CustID"))

C#

CustomerOrders.Relations.Add ("CustOrders", customerOrders.Tables ["Customers"] .Columns ["CustID"], customerOrders.Tables ["Orders"] .Columns ["CustID"])

ADO.NET DataRelation also has the Nested attribute, and if this attribute is set to true, rows from the child table are nested in the associated rows from the parent table when they are written as XML elements using WriteXml.

Thank you for reading! This is the end of this article on "how to use DataRelation objects in ADO.NET". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it for more people to see!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.