Cómo: Ejecutar consultas por lotes (WCF Data Services)
La biblioteca de cliente de WCF Data Services le permite ejecutar más de una consulta en el servicio de datos de un solo lote. Para obtener más información, vea Realizar operaciones por lotes (WCF Data Services).
En el ejemplo de este tema se usa el servicio de datos de ejemplo Northwind y las clases del servicio de datos del cliente generadas automáticamente. Se crean este servicio y las clases de datos del cliente al completar el tutorial rápido de WCF Data Services.
Ejemplo
En el ejemplo siguiente se muestra cómo llamar al método ExecuteBatch para ejecutar una matriz de los objetos DataServiceRequest que contiene consultas que devuelven objetos Products y Customers del servicio de datos de Northwind. La colección de objetos QueryOperationResponse del objeto DataServiceResponse devuelto es de tipo enumerado y la colección de objetos contenida en cada QueryOperationResponse también lo es.
Dim customerId = "ALFKI"
' Create the DataServiceContext using the service URI.
Dim context = New NorthwindEntities(svcUri)
' Create the separate query URI's, one that returns
' a single customer and another that returns all Products.
Dim customerUri = New Uri(svcUri.AbsoluteUri & _
"/Customers('" & customerId & "')/?$expand=Orders")
Dim productsUri = New Uri(svcUri.AbsoluteUri & _
"/Products")
' Create the query requests.
Dim customerQuery = New DataServiceRequest(Of Customer)(customerUri)
Dim productsQuery = New DataServiceRequest(Of Product)(productsUri)
' Add the query requests to a batch request array.
Dim batchRequests = _
New DataServiceRequest() {customerQuery, productsQuery}
Dim batchResponse As DataServiceResponse
Try
' Execute the query batch and get the response.
batchResponse = context.ExecuteBatch(batchRequests)
If batchResponse.IsBatchResponse Then
' Parse the batchResponse.BatchHeaders.
End If
' Enumerate over the results of the query.
For Each response As QueryOperationResponse In batchResponse
' Handle an error response.
If response.StatusCode > 299 OrElse response.StatusCode < 200 Then
Console.WriteLine("An error occurred.")
Console.WriteLine(response.Error.Message)
Else
' Find the response for the Customers query.
If response.Query.ElementType Is GetType(Customer) Then
For Each customer As Customer In response
Console.WriteLine("Customer: {0}", customer.CompanyName)
For Each order As Order In customer.Orders
Console.WriteLine("Order ID: {0} - Freight: {1}", _
order.OrderID, order.Freight)
Next
Next
' Find the response for the Products query.
ElseIf response.Query.ElementType Is GetType(Product) Then
For Each product As Product In response
Console.WriteLine("Product: {0}", product.ProductName)
Next
End If
End If
Next
' This type of error is raised when the data service returns with
' a response code < 200 or >299 in the top level element.
Catch ex As DataServiceRequestException
' Get the response from the exception.
batchResponse = ex.Response
If (batchResponse.IsBatchResponse) Then
' Parse the batchResponse.BatchHeaders.
End If
For Each response As QueryOperationResponse In batchResponse
If response.Error IsNot Nothing Then
Console.WriteLine("An error occurred.")
Console.WriteLine(response.Error.Message)
End If
Next
End Try
string customerId = "ALFKI";
// Create the DataServiceContext using the service URI.
NorthwindEntities context = new NorthwindEntities(svcUri);
// Create the separate query URI's, one that returns
// a single customer and another that returns all Products.
Uri customerUri = new Uri(svcUri.AbsoluteUri +
"/Customers('" + customerId + "')/?$expand=Orders");
Uri productsUri = new Uri(svcUri.AbsoluteUri +
"/Products");
// Create the query requests.
DataServiceRequest<Customer> customerQuery =
new DataServiceRequest<Customer>(customerUri);
DataServiceRequest<Product> productsQuery =
new DataServiceRequest<Product>(productsUri);
// Add the query requests to a batch request array.
DataServiceRequest[] batchRequests =
new DataServiceRequest[]{customerQuery, productsQuery};
DataServiceResponse batchResponse;
try
{
// Execute the query batch and get the response.
batchResponse = context.ExecuteBatch(batchRequests);
if (batchResponse.IsBatchResponse)
{
// Parse the batchResponse.BatchHeaders.
}
// Enumerate over the results of the query.
foreach (QueryOperationResponse response in batchResponse)
{
// Handle an error response.
if (response.StatusCode > 299 || response.StatusCode < 200)
{
Console.WriteLine("An error occurred.");
Console.WriteLine(response.Error.Message);
}
else
{
// Find the response for the Customers query.
if (response.Query.ElementType == typeof(Customer))
{
foreach (Customer customer in response)
{
Console.WriteLine("Customer: {0}", customer.CompanyName);
foreach (Order order in customer.Orders)
{
Console.WriteLine("Order ID: {0} - Freight: {1}",
order.OrderID, order.Freight);
}
}
}
// Find the response for the Products query.
else if (response.Query.ElementType == typeof(Product))
{
foreach (Product product in response)
{
Console.WriteLine("Product: {0}", product.ProductName);
}
}
}
}
}
// This type of error is raised when the data service returns with
// a response code < 200 or >299 in the top level element.
catch (DataServiceRequestException e)
{
// Get the response from the exception.
batchResponse = e.Response;
if (batchResponse.IsBatchResponse)
{
// Parse the batchResponse.BatchHeaders.
}
foreach (QueryOperationResponse response in batchResponse)
{
if (response.Error != null)
{
Console.WriteLine("An error occurred.");
Console.WriteLine(response.Error.Message);
}
}
}