Cómo usar rutas de la consulta para dar forma a los resultados (Entity Framework)
En este tema se proporciona un ejemplo de cómo especificar una ruta de la consulta que defina qué objetos relacionados se devuelven cuando se consulta un objeto concreto en Entity Data Model (EDM). La consulta de este ejemplo devuelve un único objeto Contact y todos los objetos SalesOrderHeader y SalesOrderDetail relacionados. Se muestra el mismo ejemplo con cada una de las siguientes tecnologías de consulta de Entity Framework:
LINQ to Entities
Entity SQL con ObjectQuery<T>
Métodos del generador de consultas de ObjectQuery<T>
El ejemplo de este tema se basa en el modelo AdventureWorks Sales. Para ejecutar el código de este ejemplo, debe haber agregado ya el modelo AdventureWorks Sales al proyecto y haber configurado el proyecto para usar Entity Framework. Para ello, complete los procedimientos de Cómo configurar manualmente un proyecto de Entity Framework y Cómo definir manualmente un modelo Entity Data Model (Entity Framework). También puede utilizar el Asistente para Entity Data Model con el fin de definir el modelo AdventureWorks Sales. Para obtener más información, vea Cómo usar el Asistente para Entity Data Model (Entity Framework).
Ejemplo
Éste es el ejemplo de LINQ to Entities.
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());
}
}
Éste es el ejemplo de Entity SQL.
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());
}
}
A continuación se muestra el ejemplo del método del generador de consultas.
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());
}
}
Vea también
Tareas
Cómo ejecutar una consulta que devuelve un tipo de entidad (Entity Framework)
Cómo navegar por las relaciones mediante propiedades de navegación (Entity Framework)
Conceptos
Dar forma a los resultados de la consulta (Entity Framework)
Métodos del generador de consultas (Entity Framework)
Información general de Entity SQL