How to: Execute a Query that Returns Nested Collections
.NET Framework 4.5
This shows how to execute a command against a conceptual model by using an EntityCommand object, and how to retrieve the nested collection results by using an EntityDataReader.
To run the code in this example
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Add the AdventureWorks Sales Model to your project and configure your project to use the Entity Framework. For more information, see How to: Use the Entity Data Model Wizard (Entity Framework).
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In the code page for your application, add the following using statements (Imports in Visual Basic):
Example
A nested collection is a collection that is inside another collection. The following code retrieves a collection of Contacts and the nested collections of SalesOrderHeaders that are associated with each Contact.
using (EntityConnection conn = new EntityConnection("name=AdventureWorksEntities")) { conn.Open(); // Create an EntityCommand. using (EntityCommand cmd = conn.CreateCommand()) { // Create a nested query. string esqlQuery = @"Select c.ContactID, c.SalesOrderHeaders From AdventureWorksEntities.Contacts as c"; cmd.CommandText = esqlQuery; // Execute the command. using (EntityDataReader rdr = cmd.ExecuteReader(CommandBehavior.SequentialAccess)) { // The result returned by this query contains // ContactID and a nested collection of SalesOrderHeader items. // associated with this Contact. while (rdr.Read()) { // the first column contains Contact ID. Console.WriteLine("Contact ID: {0}", rdr["ContactID"]); // The second column contains a collection of SalesOrderHeader // items associated with the Contact. DbDataReader nestedReader = rdr.GetDataReader(1); while (nestedReader.Read()) { Console.WriteLine(" SalesOrderID: {0} ", nestedReader["SalesOrderID"]); Console.WriteLine(" OrderDate: {0} ", nestedReader["OrderDate"]); } } } } conn.Close(); }
See Also
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