Procedura: aggiungere, modificare ed eliminare entità (WCF Data Services)

Con le librerie client di WCF Data Services è possibile creare, aggiornare ed eliminare dati di entità in un servizio dati eseguendo azioni equivalenti sugli oggetti in DataServiceContext. Per ulteriori informazioni, vedere Aggiornamento del servizio dati (WCF Data Services).

Nell'esempio riportato in questo argomento vengono utilizzati il servizio dati Northwind di esempio e le classi del servizio dati client generate automaticamente. Questo servizio e le classi di dati client vengono creati al completamento della Guida rapida di WCF Data Services.

Esempio

Nell'esempio seguente viene creato una nuova istanza dell'oggetto e viene quindi chiamato il metodo AddObject sull'oggetto DataServiceContext per creare l'elemento nel contesto. Un messaggio POST HTTP viene inviato al servizio dati al momento della chiamata del metodo SaveChanges.

' Create the DataServiceContext using the service URI.
Dim context = New NorthwindEntities(svcUri)

' Create the new product.
Dim newProduct = _
    Product.CreateProduct(0, "White Tea - loose", False)

' Set property values.
newProduct.QuantityPerUnit = "120gm bags"
newProduct.ReorderLevel = 5
newProduct.UnitPrice = 5.2D

Try
    ' Add the new product to the Products entity set.
    context.AddToProducts(newProduct)

    ' Send the insert to the data service.
    context.SaveChanges()

    Console.WriteLine("New product added with ID {0}.", newProduct.ProductID)
Catch ex As DataServiceRequestException
    Throw New ApplicationException( _
            "An error occurred when saving changes.", ex)

// Create the DataServiceContext using the service URI.
NorthwindEntities context = new NorthwindEntities(svcUri);

// Create the new product.
Product newProduct =
    Product.CreateProduct(0, "White Tea - loose", false);

// Set property values.
newProduct.QuantityPerUnit = "120gm bags";
newProduct.ReorderLevel = 5;
newProduct.UnitPrice = 5.2M;

try
{
    // Add the new product to the Products entity set.
    context.AddToProducts(newProduct);

    // Send the insert to the data service.
    DataServiceResponse response = context.SaveChanges();

    // Enumerate the returned responses.
    foreach (ChangeOperationResponse change in response)
    {
        // Get the descriptor for the entity.
        EntityDescriptor descriptor = change.Descriptor as EntityDescriptor;

        if (descriptor != null)
        {
            Product addedProduct = descriptor.Entity as Product;

            if (addedProduct != null)
            {
                Console.WriteLine("New product added with ID {0}.",
                    addedProduct.ProductID);
            }
        }
    }
}
catch (DataServiceRequestException ex)
{
    throw new ApplicationException(
        "An error occurred when saving changes.", ex);
}

Nell'esempio seguente viene recuperato e modificato un oggetto esistente e viene quindi chiamato il metodo UpdateObject sull'oggetto DataServiceContext per contrassegnare l'elemento come aggiornato. Un messaggio MERGE HTTP viene inviato al servizio dati al momento della chiamata del metodo SaveChanges.

Dim customerId = "ALFKI"

' Create the DataServiceContext using the service URI.
Dim context = New NorthwindEntities(svcUri)

' Get a customer to modify using the supplied ID.
Dim customerToChange = (From customer In context.Customers _
                        Where customer.CustomerID = customerId _
                        Select customer).Single()

' Change some property values.
customerToChange.CompanyName = "Alfreds Futterkiste"
customerToChange.ContactName = "Maria Anders"
customerToChange.ContactTitle = "Sales Representative"

Try
    ' Mark the customer as updated.
    context.UpdateObject(customerToChange)

    ' Send the update to the data service.
    context.SaveChanges()
Catch ex As DataServiceRequestException
    Throw New ApplicationException( _
            "An error occurred when saving changes.", ex)
End Try

string customerId = "ALFKI";

// Create the DataServiceContext using the service URI.
NorthwindEntities context = new NorthwindEntities(svcUri);

// Get a customer to modify using the supplied ID.
var customerToChange = (from customer in context.Customers
                        where customer.CustomerID == customerId
                        select customer).Single();

// Change some property values.
customerToChange.CompanyName = "Alfreds Futterkiste";
customerToChange.ContactName = "Maria Anders";
customerToChange.ContactTitle = "Sales Representative";

try
{
    // Mark the customer as updated.
    context.UpdateObject(customerToChange);

    // Send the update to the data service.
    context.SaveChanges();
}
catch (DataServiceRequestException  ex)
{
    throw new ApplicationException(
        "An error occurred when saving changes.", ex);
}

Nell'esempio seguente viene chiamato il metodo DeleteObject sull'oggetto DataServiceContext per contrassegnare l'elemento nel contesto come eliminato. Un messaggio DELETE HTTP viene inviato al servizio dati al momento della chiamata del metodo SaveChanges.

' Create the DataServiceContext using the service URI.
Dim context = New NorthwindEntities(svcUri)

Try
    ' Get the product to delete, by product ID.
    Dim deletedProduct = (From product In context.Products _
                          Where product.ProductID = productID _
                          Select product).Single()


    ' Mark the product for deletion.    
    context.DeleteObject(deletedProduct)

    ' Send the delete to the data service.
    context.SaveChanges()

    ' Handle the error that occurs when the delete operation fails,
    ' which can happen when there are entities with existing 
    ' relationships to the product being deleted.
Catch ex As DataServiceRequestException
    Throw New ApplicationException( _
            "An error occurred when saving changes.", ex)
End Try

// Create the DataServiceContext using the service URI.
NorthwindEntities context = new NorthwindEntities(svcUri);

try
{
    // Get the product to delete, by product ID.
    var deletedProduct = (from product in context.Products
                          where product.ProductID == productID
                          select product).Single();

    // Mark the product for deletion.    
    context.DeleteObject(deletedProduct);

    // Send the delete to the data service.
    context.SaveChanges();
}
// Handle the error that occurs when the delete operation fails,
// which can happen when there are entities with existing 
// relationships to the product being deleted.
catch (DataServiceRequestException ex)
{
    throw new ApplicationException(
        "An error occurred when saving changes.", ex);
}

Nell'esempio seguente viene creato una nuova istanza dell'oggetto e viene quindi chiamato il metodo AddRelatedObject sull'oggetto DataServiceContext per creare l'elemento nel contesto insieme al collegamento all'ordine correlato. Un messaggio POST HTTP viene inviato al servizio dati al momento della chiamata del metodo SaveChanges.

Dim productId = 25
Dim customerId = "ALFKI"

Dim newItem As Order_Detail = Nothing

' Create the DataServiceContext using the service URI.
Dim context = New NorthwindEntities(svcUri)

Try
    ' Get the specific product.
    Dim selectedProduct = (From product In context.Products _
                           Where product.ProductID = productId _
                           Select product).Single()

    ' Get the specific customer.
    Dim cust = (From customer In context.Customers.Expand("Orders") _
                Where customer.CustomerID = customerId _
                Select customer).Single()

    ' Get the first order. 
    Dim order = cust.Orders.FirstOrDefault()

    ' Create a new order detail for the specific product.
    newItem = Order_Detail.CreateOrder_Detail( _
            order.OrderID, selectedProduct.ProductID, 10, 5, 0)

    ' Add the new item with a link to the related order.
    context.AddRelatedObject(order, "Order_Details", newItem)

    ' Add the new order detail to the collection, and
    ' set the reference to the product.
    order.Order_Details.Add(newItem)
    newItem.Order = order
    newItem.Product = selectedProduct

    ' Send the changes to the data service.
    Dim response As DataServiceResponse = context.SaveChanges()

    ' Enumerate the returned responses.
    For Each change As ChangeOperationResponse In response
        ' Get the descriptor for the entity.
        Dim descriptor = TryCast(change.Descriptor, EntityDescriptor)

        If Not descriptor Is Nothing Then
            If TypeOf descriptor.Entity Is Order_Detail Then
                Dim addedItem = TryCast(descriptor.Entity, Order_Detail)

                If Not addedItem Is Nothing Then
                    Console.WriteLine("New {0} item added to order {1}.", _
                        addedItem.Product.ProductName, addedItem.OrderID.ToString())
                End If
            End If
        End If
    Next
Catch ex As DataServiceQueryException
    Throw New ApplicationException( _
            "An error occurred when saving changes.", ex)

    ' Handle any errors that may occur during insert, such as 
    ' a constraint violation.
Catch ex As DataServiceRequestException
    Throw New ApplicationException( _
            "An error occurred when saving changes.", ex)

int productId = 25;
string customerId = "ALFKI";

Order_Detail newItem = null;

// Create the DataServiceContext using the service URI.
NorthwindEntities context = new NorthwindEntities(svcUri);

try
{
    // Get the specific product.
    var selectedProduct = (from product in context.Products
                           where product.ProductID == productId
                           select product).Single();

    // Get the specific customer.
    var cust = (from customer in context.Customers.Expand("Orders")
                where customer.CustomerID == customerId
                select customer).Single();

    // Get the first order. 
    Order order = cust.Orders.FirstOrDefault();

    // Create a new order detail for the specific product.
    newItem = Order_Detail.CreateOrder_Detail(
        order.OrderID, selectedProduct.ProductID, 10, 5, 0);

    // Add the new item with a link to the related order.
    context.AddRelatedObject(order, "Order_Details", newItem);

    // Add the new order detail to the collection, and
    // set the reference to the product.
    order.Order_Details.Add(newItem);
    newItem.Order = order;
    newItem.Product = selectedProduct;

    // Send the changes to the data service.
    DataServiceResponse response = context.SaveChanges();

    // Enumerate the returned responses.
    foreach (ChangeOperationResponse change in response)
    {
        // Get the descriptor for the entity.
        EntityDescriptor descriptor = change.Descriptor as EntityDescriptor;

        if (descriptor != null)
        {
            if (descriptor.Entity.GetType() == typeof(Order_Detail))
            {
                Order_Detail addedItem = descriptor.Entity as Order_Detail;

                if (addedItem != null)
                {
                    Console.WriteLine("New {0} item added to order {1}.", 
                        addedItem.Product.ProductName, addedItem.OrderID.ToString());
                }
            }
        }
    }
}
catch (DataServiceQueryException ex)
{
    throw new ApplicationException(
        "An error occurred when saving changes.", ex);
}

// Handle any errors that may occur during insert, such as 
// a constraint violation.
catch (DataServiceRequestException ex)
{
    throw new ApplicationException(
        "An error occurred when saving changes.", ex);
}

Vedere anche

Attivitá

Procedura: collegare un'entità esistente a DataServiceContext (WCF Data Services)

Procedura: definire relazioni tra entità (WCF Data Services)

Concetti

Invio in batch di operazioni (WCF Data Services)

Altre risorse

Client dati (WCF Data Services)