方法: クエリをバッチで実行する (WCF Data Services)
WCF Data Services クライアント ライブラリを使用すると、データ サービスに対する複数のクエリを 1 つのバッチで実行できます。 詳細については、「バッチ処理 (WCF Data Services)」を参照してください。
このトピックの例では、Northwind サンプル データ サービスおよび自動生成されたクライアント データ サービス クラスを使用します。 このサービスおよびクライアント データ クラスは、WCF Data Services クイック スタートを完了したときに作成されます。
使用例
次の例は、ExecuteBatch メソッドを呼び出して、Customers オブジェクトと Products オブジェクトの両方を Northwind データ サービスから返すクエリを含む DataServiceRequest<TElement> オブジェクトの配列を実行する方法を示します。 返された DataServiceResponse 内の QueryOperationResponse<T> オブジェクトのコレクションが列挙され、各 QueryOperationResponse<T> に含まれるオブジェクトのコレクションも列挙されます。
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);
}
}
}