查詢運算式語法範例：巡覽關聯性 (LINQ to Entities)
實體資料模型 (EDM) 中的導覽屬性是用來尋找位於關聯結尾之實體的捷徑屬性。 導覽屬性可讓使用者在不同實體之間巡覽，或是透過關聯集合從某個實體巡覽至相關的實體。 本主題提供的查詢運算式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" 之每位連絡人總金額的總和。 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總金額。
Using AWEntities As New AdventureWorksEntities
Dim contacts As ObjectQuery(Of Contact) = AWEntities.Contact
Dim ordersQuery = From contact In contacts _
Where contact.LastName = "Zhou" _
Select New With _
{.ContactID = contact.ContactID, _
.Total = contact.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())
{
ObjectQuery<Contact> contacts = AWEntities.Contact;
var ordersQuery = from contact in contacts
where contact.LastName == "Zhou"
select new
{
ContactID = contact.ContactID,
Total = contact.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 contacts As ObjectQuery(Of Contact) = AWEntities.Contact
Dim ordersQuery = From contact In contacts _
Where contact.LastName = "Zhou" _
Select New With _
{.LastName = contact.LastName, _
.Orders = contact.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())
{
ObjectQuery<Contact> contacts = AWEntities.Contact;
var ordersQuery = from contact in contacts
where contact.LastName == "Zhou"
select new { LastName = contact.LastName, Orders = contact.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 orders As ObjectQuery(Of SalesOrderHeader) = AWEntities.SalesOrderHeader
Dim ordersQuery = From order In orders _
Where order.Address.City = "Seattle" _
Select New With { _
.ContactLastName = order.Contact.LastName, _
.ContactFirstName = order.Contact.FirstName, _
.StreetAddress = order.Address.AddressLine1, _
.OrderNumber = order.SalesOrderNumber, _
.TotalDue = order.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())
{
ObjectQuery<SalesOrderHeader> orders = AWEntities.SalesOrderHeader;
var ordersQuery = from order in orders
where order.Address.City == "Seattle"
select new
{
ContactLastName = order.Contact.LastName,
ContactFirstName = order.Contact.FirstName,
StreetAddress = order.Address.AddressLine1,
OrderNumber = order.SalesOrderNumber,
TotalDue = order.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);
}
}
}