HOW TO：執行可傳回巢狀集合的查詢 (EntityClient)

本主題提供的範例將說明如何藉由使用 EntityCommand 對 Entity Data Model 執行命令，以及如何藉由使用 EntityDataReader 擷取巢狀集合結果。

若要執行這個範例中的程式碼

1. 將 AdventureWorks Sales Model 加入至專案中，並將專案設定成使用 Entity Framework。若要這麼做，必須執行下列其中一項：

   • 如果已經安裝 Entity Dada Model 工具，請完成 HOW TO：使用 Entity Data Model 精靈 (Entity Framework) 中的程序。

   • 不然的話，請完成 HOW TO：手動設定 Entity Framework 專案和 HOW TO：以手動方式定義 Entity Data Model (Entity Framework) 中的程序。

2. 在應用程式的字碼頁中加入下列 using 陳述式 (在 Visual Basic 中為 Imports)：

   Imports System
   Imports System.Collections.Generic
   Imports System.Collections
   Imports System.Data.Common
   Imports System.Data
   Imports System.Data.SqlClient
   Imports System.Data.EntityClient
   Imports System.Data.Metadata.Edm
   Imports System.IO
   ' Add AdventureWorksModel prepended with the root namespace for the project.
   'Imports ProjectName.AdventureWorksModel
   

   using System;
   using System.Collections.Generic;
   using System.Collections;
   using System.Data.Common;
   using System.Data;
   using System.IO;
   using System.Data.SqlClient;
   using System.Data.EntityClient;
   using AdventureWorksModel;
   using System.Data.Metadata.Edm;
   

範例

「巢狀集合」(Nested Collection) 是某個位於另一個集合內的集合。下列程式碼會擷取 Contacts 的集合以及與每一個 Contact 有關聯的 SalesOrderHeaders 巢狀集合。

Using conn As EntityConnection = New EntityConnection("name=AdventureWorksEntities")
    conn.Open()
    Try
        ' Create an EntityCommand.
        Using cmd As EntityCommand = conn.CreateCommand()

            ' Create a nested query.
            Dim esqlQuery As String = "Select c.ContactID, c.SalesOrderHeader " & _
                    "From AdventureWorksEntities.Contact as c"

            cmd.CommandText = esqlQuery
            ' Execute the command.
            Using rdr As EntityDataReader = cmd.ExecuteReader(CommandBehavior.SequentialAccess)
                ' The result returned by this query contains 
                ' ContactID and a nested collection of SalesOrderHeader items.
                ' associated with this Contact.
                Do While rdr.Read
                    ' the first column contains Contact ID.
                    Console.WriteLine("Contact ID: {0}", rdr.Item("ContactID"))

                    ' The second column contains a collection of SalesOrderHeader 
                    ' items associated with the Contact.
                    Dim nestedReader As DbDataReader = rdr.GetDataReader(1)
                    Do While nestedReader.Read
                        Console.WriteLine("   SalesOrderID: {0} ", nestedReader.Item("SalesOrderID"))
                        Console.WriteLine("   OrderDate: {0} ", nestedReader.Item("OrderDate"))
                    Loop
                Loop
            End Using
        End Using
    Catch ex As EntityException
        Console.WriteLine(ex.ToString())
    End Try

    conn.Close()
End Using

using (EntityConnection conn =
    new EntityConnection("name=AdventureWorksEntities"))
{
    conn.Open();
    try
    {
        // Create an EntityCommand.
        using (EntityCommand cmd = conn.CreateCommand())
        {
            // Create a nested query.
            string esqlQuery =
                @"Select c.ContactID, c.SalesOrderHeader
            From AdventureWorksEntities.Contact 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"]);
                    }
                }
            }
        }
    }
    catch (EntityException ex)
    {
        Console.WriteLine(ex.ToString());
    }
    conn.Close();
}

另請參閱

其他資源

使用 EntityClient (Entity Framework 工作)