HOW TO：使用查詢路徑來設定結果外觀 (Entity Framework)
本主題提供的範例將示範如何指定查詢路徑，以便定義在 Entity Data Model (EDM) 中查詢特定物件時所傳回的相關物件。這個範例中的查詢會傳回單一 Contact 物件，以及所有相關的 SalesOrderHeader 和 SalesOrderDetail 物件。此外，也會顯示使用下列每一個 實體架構 查詢技術的相同範例：
LINQ to Entities
使用 ObjectQuery<T> 的 Entity SQL
ObjectQuery<T> 的查詢產生器方法
本主題的範例是根據 Adventure Works Sales Model。若要執行此範例中的程式碼，您必須已經將 AdventureWorks Sales Model 加入到專案中，並設定您的專案使用 Entity Framework。若要這樣做，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。您也可以使用 [Entity Data Model 精靈] 定義 AdventureWorks Sales Model。如需詳細資訊，請參閱 HOW TO：使用 Entity Data Model 精靈 (Entity Framework)。
範例
這是 LINQ 到實體 範例。
Using context As New AdventureWorksEntities
' Define a LINQ query with a path that returns
' orders and items for a contact.
Dim contacts = (From contact In context.Contact _
.Include("SalesOrderHeader.SalesOrderDetail") _
Select contact).FirstOrDefault()
Try
' Execute the query and display information for each item
' in the orders that belong to the contact.
For Each order As SalesOrderHeader In contacts.SalesOrderHeader
Console.WriteLine(String.Format("PO Number: {0}", _
order.PurchaseOrderNumber))
Console.WriteLine(String.Format("Order Date: {0}", _
order.OrderDate.ToString()))
Console.WriteLine("Order items:")
For Each item As SalesOrderDetail In order.SalesOrderDetail
Console.WriteLine(String.Format("Product:{0}" _
+ "Quantity: {1}", item.ProductID.ToString(), _
item.OrderQty.ToString()))
Next
Next
Catch ex As EntitySqlException
Console.WriteLine(ex.ToString())
Catch ex As EntityCommandExecutionException
Console.WriteLine(ex.ToString())
End Try
End Using
using (AdventureWorksEntities context =
new AdventureWorksEntities())
{
// Define a LINQ query with a path that returns
// orders and items for a contact.
var contacts = (from contact in context.Contact
.Include("SalesOrderHeader.SalesOrderDetail")
select contact).FirstOrDefault();
try
{
// Execute the query and display information for each item
// in the orders that belong to the contact.
foreach (SalesOrderHeader order in contacts
.SalesOrderHeader)
{
Console.WriteLine(String.Format("PO Number: {0}",
order.PurchaseOrderNumber));
Console.WriteLine(String.Format("Order Date: {0}",
order.OrderDate.ToString()));
Console.WriteLine("Order items:");
foreach (SalesOrderDetail item in order.SalesOrderDetail)
{
Console.WriteLine(String.Format("Product: {0} "
+ "Quantity: {1}", item.ProductID.ToString(),
item.OrderQty.ToString()));
}
}
}
catch (EntitySqlException ex)
{
Console.WriteLine(ex.ToString());
}
catch (EntityCommandExecutionException ex)
{
Console.WriteLine(ex.ToString());
}
}
這是 實體 SQL 範例。
Using context As New AdventureWorksEntities
' Define an object query with a path that returns
' orders and items for a specific contact.
Dim queryString As String = _
"SELECT VALUE TOP(1) Contact FROM " + _
"AdventureWorksEntities.Contact AS Contact"
' Define the object query with the query string.
Dim contactQuery As New ObjectQuery(Of Contact)(queryString, _
context, MergeOption.NoTracking)
Dim contact As Contact = _
contactQuery.Include("SalesOrderHeader.SalesOrderDetail") _
.FirstOrDefault()
Try
' Execute the query and display information for each item
' in the orders that belong to the first contact.
For Each order As SalesOrderHeader In contact.SalesOrderHeader
Console.WriteLine(String.Format("PO Number: {0}", _
order.PurchaseOrderNumber))
Console.WriteLine(String.Format("Order Date: {0}", _
order.OrderDate.ToString()))
Console.WriteLine("Order items:")
For Each item As SalesOrderDetail In order.SalesOrderDetail
Console.WriteLine(String.Format("Product:{0}" _
+ "Quantity: {1}", item.ProductID.ToString(), _
item.OrderQty.ToString()))
Next
Next
Catch ex As EntitySqlException
Console.WriteLine(ex.ToString())
Catch ex As EntityCommandExecutionException
Console.WriteLine(ex.ToString())
End Try
End Using
using (AdventureWorksEntities context =
new AdventureWorksEntities())
{
// Define an object query with a path that returns
// orders and items for a specific contact.
string queryString =
@"SELECT VALUE TOP(1) Contact FROM " +
"AdventureWorksEntities.Contact AS Contact";
// Define the object query with the query string.
ObjectQuery<Contact> contactQuery = new ObjectQuery<Contact>(queryString,
context, MergeOption.NoTracking);
Contact contact =
contactQuery.Include("SalesOrderHeader.SalesOrderDetail")
.FirstOrDefault();
try
{
// Execute the query and display information for each item
// in the orders that belong to the first contact.
foreach (SalesOrderHeader order in contact
.SalesOrderHeader)
{
Console.WriteLine(String.Format("PO Number: {0}",
order.PurchaseOrderNumber));
Console.WriteLine(String.Format("Order Date: {0}",
order.OrderDate.ToString()));
Console.WriteLine("Order items:");
foreach (SalesOrderDetail item in order.SalesOrderDetail)
{
Console.WriteLine(String.Format("Product: {0} "
+ "Quantity: {1}", item.ProductID.ToString(),
item.OrderQty.ToString()));
}
}
}
catch (EntitySqlException ex)
{
Console.WriteLine(ex.ToString());
}
catch (EntityCommandExecutionException ex)
{
Console.WriteLine(ex.ToString());
}
}
這是查詢產生器方法範例。
Using context As New AdventureWorksEntities
' Create an object query with a path that returns orders and items for a contact.
Dim contact As Contact = _
context.Contact.Include("SalesOrderHeader.SalesOrderDetail") _
.FirstOrDefault()
Try
' Execute the query and display information for each item
' in the orders that belong to the returned contact.
Dim order As SalesOrderHeader
For Each order In contact.SalesOrderHeader
Console.WriteLine(String.Format("PO Number: {0}", _
order.PurchaseOrderNumber))
Console.WriteLine(String.Format("Order Date: {0}", _
order.OrderDate.ToString()))
Console.WriteLine("Order items:")
Dim item As SalesOrderDetail
For Each item In order.SalesOrderDetail
Console.WriteLine(String.Format("Product:{0}" _
+ "Quantity: {1}", item.ProductID.ToString(), _
item.OrderQty.ToString()))
Next
Next
Catch ex As EntitySqlException
Console.WriteLine(ex.ToString())
Catch ex As EntityCommandExecutionException
Console.WriteLine(ex.ToString())
End Try
End Using
using (AdventureWorksEntities context =
new AdventureWorksEntities())
{
// Define an object query with a path that returns
// orders and items for a specific contact.
Contact contact =
context.Contact.Include("SalesOrderHeader.SalesOrderDetail")
.FirstOrDefault();
try
{
// Execute the query and display information for each item
// in the orders that belong to the first contact.
foreach (SalesOrderHeader order in contact
.SalesOrderHeader)
{
Console.WriteLine(String.Format("PO Number: {0}",
order.PurchaseOrderNumber));
Console.WriteLine(String.Format("Order Date: {0}",
order.OrderDate.ToString()));
Console.WriteLine("Order items:");
foreach (SalesOrderDetail item in order.SalesOrderDetail)
{
Console.WriteLine(String.Format("Product: {0} "
+ "Quantity: {1}", item.ProductID.ToString(),
item.OrderQty.ToString()));
}
}
}
catch (EntitySqlException ex)
{
Console.WriteLine(ex.ToString());
}
catch (EntityCommandExecutionException ex)
{
Console.WriteLine(ex.ToString());
}
}
另請參閱
工作
HOW TO：執行傳回實體類型的查詢 (Entity Framework)
HOW TO：使用導覽屬性巡覽關聯性 (Entity Framework)
概念
為查詢結果定形 (Entity Framework)
查詢產生器方法 (Entity Framework)
Entity SQL 概觀