以方法為基礎的查詢語法範例：巡覽關聯性 (LINQ to Entities)

發行項
08/21/2008

實體資料模型 (EDM) 中的導覽屬性是用來尋找位於關聯兩端之實體的捷徑屬性。導覽屬性可讓使用者在不同實體之間巡覽，或是透過關聯集從某個實體巡覽至相關的實體。本主題提供之以方法為基礎的查詢語法範例，將說明如何透過 LINQ 到實體查詢中的導覽屬性來巡覽關聯性。

這些範例中使用的 AdventureWorks Sales Model 是從 AdventureWorks 範例資料庫中的 Contact、Address、Product、SalesOrderHeader 和 SalesOrderDetail 資料表所建立。

此主題中的範例將使用下列 using/Imports 陳述式：

Option Explicit On
Option Strict On
Imports L2EExamplesVB.AdventureWorksModel
Imports System.Data.Objects
Imports System.Globalization

using System;
using System.Data;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Objects;
using AdventureWorksModel;
using System.Globalization;

如需詳細資訊，請參閱 HOW TO：在 Visual Studio 中建立 LINQ to Entities 專案。

範例

下列以方法為基礎的查詢語法範例會使用 SelectMany 方法取得姓氏為 "Zhou" 之連絡人的所有訂單。 Contact.SalesOrderHeader 導覽屬性是用來取得每一個連絡人之 SalesOrderHeader 物件的集合。

Using AWEntities As New AdventureWorksEntities
    Dim ordersQuery = AWEntities.Contact _
    .Where(Function(c) c.LastName = "Zhou") _
    .SelectMany(Function(o) o.SalesOrderHeader)

    For Each order In ordersQuery
        Console.WriteLine("Order ID: {0}, Order date: {1}, Total Due: {2}", _
                order.SalesOrderID, order.OrderDate, order.TotalDue)
    Next
End Using

using (AdventureWorksEntities AWEntities = new AdventureWorksEntities())
{
    IQueryable<SalesOrderHeader> ordersQuery = AWEntities.Contact
        .Where(c => c.LastName == "Zhou")
        .SelectMany(c => c.SalesOrderHeader);

    foreach (var order in ordersQuery)
    {
        Console.WriteLine("Order ID: {0}, Order date: {1}, Total Due: {2}",
            order.SalesOrderID, order.OrderDate, order.TotalDue);
    }
}

範例

下列以方法為基礎的查詢語法範例會使用 Select 方法來取得所有連絡人識別碼以及姓氏為 "Zhou" 之每位連絡人的應付總額。 Contact.SalesOrderHeader 導覽屬性是用來取得每一個連絡人之 SalesOrderHeader 物件的集合。 Sum 方法會使用 Contact.SalesOrderHeader 導覽屬性來加總每位連絡人之所有訂單的應付總額。

Using AWEntities As New AdventureWorksEntities
    Dim ordersQuery = AWEntities.Contact _
    .Where(Function(c) c.LastName = "Zhou") _
    .Select(Function(c) New With _
                {.ContactID = c.ContactID, _
                .Total = c.SalesOrderHeader.Sum(Function(o) o.TotalDue)})

    For Each order In ordersQuery
        Console.WriteLine("Contact ID: {0} Orders total: {1}", order.ContactID, order.Total)
    Next
End Using

using (AdventureWorksEntities AWEntities = new AdventureWorksEntities())
{
    var ordersQuery = AWEntities.Contact
        .Where(c => c.LastName == "Zhou")
        .Select(c => new
        {
            ContactID = c.ContactID,
            Total = c.SalesOrderHeader.Sum(o => o.TotalDue)
        });

    foreach (var contact in ordersQuery)
    {
        Console.WriteLine("Contact ID: {0} Orders total: {1}", contact.ContactID, contact.Total);
    }
}

範例

下列以方法為基礎之查詢語法的範例會取得姓氏為 "Zhou" 之連絡人的所有訂單。 Contact.SalesOrderHeader 導覽屬性是用來取得每一個連絡人之 SalesOrderHeader 物件的集合。該連絡人的名稱和訂單會以匿名型別的形式傳回。

Using AWEntities As New AdventureWorksEntities
    Dim ordersQuery = AWEntities.Contact _
    .Where(Function(c) c.LastName = "Zhou") _
    .Select(Function(o) New With _
                {.LastName = o.LastName, _
                 .Orders = o.SalesOrderHeader})

    For Each order In ordersQuery
        Console.WriteLine("Name: {0}", order.LastName)
        For Each orderInfo In order.Orders

            Console.WriteLine("Order ID: {0}, Order date: {1}, Total Due: {2}", _
                    orderInfo.SalesOrderID, orderInfo.OrderDate, orderInfo.TotalDue)
        Next

        Console.WriteLine("")
    Next
End Using

using (AdventureWorksEntities AWEntities = new AdventureWorksEntities())
{
    var ordersQuery = AWEntities.Contact
        .Where(c => c.LastName == "Zhou")
        .Select(c => new { LastName = c.LastName, Orders = c.SalesOrderHeader });

    foreach (var order in ordersQuery)
    {
        Console.WriteLine("Name: {0}", order.LastName);
        foreach (SalesOrderHeader orderInfo in order.Orders)
        {
            Console.WriteLine("Order ID: {0}, Order date: {1}, Total Due: {2}",
                orderInfo.SalesOrderID, orderInfo.OrderDate, orderInfo.TotalDue);
        }
        Console.WriteLine("");
    }
}

範例

下列範例會使用 SalesOrderHeader.Address 和 SalesOrderHeader.Contact 導覽屬性來取得與每筆訂單相關聯之 Address 和 Contact 物件的集合。到西雅圖城市之每一筆訂單的連絡人姓氏、街道地址、銷售訂單編號及應付總額會以匿名型別的形式傳回。

Using AWEntities As New AdventureWorksEntities
    Dim ordersQuery = AWEntities.SalesOrderHeader _
             .Where(Function(o) o.Address.City = "Seattle") _
             .Select(Function(o) New With { _
                            .ContactLastName = o.Contact.LastName, _
                            .ContactFirstName = o.Contact.FirstName, _
                            .StreetAddress = o.Address.AddressLine1, _
                            .OrderNumber = o.SalesOrderNumber, _
                            .TotalDue = o.TotalDue _
             })

    For Each orderInfo In ordersQuery
        Console.WriteLine("Name: {0}, {1}", orderInfo.ContactLastName, orderInfo.ContactFirstName)
        Console.WriteLine("Street address: {0}", orderInfo.StreetAddress)
        Console.WriteLine("Order number: {0}", orderInfo.OrderNumber)
        Console.WriteLine("Total Due: {0}", orderInfo.TotalDue)
        Console.WriteLine("")
    Next

End Using

using (AdventureWorksEntities AWEntities = new AdventureWorksEntities())
{
    var ordersQuery = AWEntities.SalesOrderHeader
        .Where(o => o.Address.City == "Seattle")
        .Select(o => new
        {
            ContactLastName = o.Contact.LastName,
            ContactFirstName = o.Contact.FirstName,
            StreetAddress = o.Address.AddressLine1,
            OrderNumber = o.SalesOrderNumber,
            TotalDue = o.TotalDue
        });

    foreach (var orderInfo in ordersQuery)
    {
        Console.WriteLine("Name: {0}, {1}", orderInfo.ContactLastName, orderInfo.ContactFirstName);
        Console.WriteLine("Street address: {0}", orderInfo.StreetAddress);
        Console.WriteLine("Order number: {0}", orderInfo.OrderNumber);
        Console.WriteLine("Total Due: {0}", orderInfo.TotalDue);
        Console.WriteLine("");
    }
}

範例

下列範例會使用 Where 方法來尋找在 2003 年 12 月 1 日之後下單的訂單，然後使用 order.SalesOrderDetail 導覽屬性來取得每筆訂單的詳細資料。

Using AWEntities As New AdventureWorksEntities
    Dim orders As ObjectQuery(Of SalesOrderHeader) = AWEntities.SalesOrderHeader

    Dim query = _
        From order In orders _
        Where order.OrderDate >= New DateTime(2003, 12, 1) _
        Select order

    Console.WriteLine("Orders that were made after December 1, 2003:")
    For Each order In query
        Console.WriteLine("OrderID {0} Order date: {1:d} ", _
                order.SalesOrderID, order.OrderDate)
        For Each orderDetail In order.SalesOrderDetail
            Console.WriteLine("  Product ID: {0} Unit Price {1}", _
                orderDetail.ProductID, orderDetail.UnitPrice)
        Next
    Next
End Using

using (AdventureWorksEntities AWEntities = new AdventureWorksEntities())
{
    ObjectQuery<SalesOrderHeader> orders = AWEntities.SalesOrderHeader;

    IQueryable<SalesOrderHeader> query =
        from order in orders
        where order.OrderDate >= new DateTime(2003, 12, 1)
        select order;


    Console.WriteLine("Orders that were made after December 1, 2003:");
    foreach (SalesOrderHeader order in query)
    {
        Console.WriteLine("OrderID {0} Order date: {1:d} ",
            order.SalesOrderID, order.OrderDate);
        foreach (SalesOrderDetail orderDetail in order.SalesOrderDetail)
        {
            Console.WriteLine("  Product ID: {0} Unit Price {1}",
                orderDetail.ProductID, orderDetail.UnitPrice);
        }
    }
}

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 以方法為基礎的查詢語法範例 (LINQ to Entities)

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以方法為基礎的查詢語法範例：巡覽關聯性 (LINQ to Entities)

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