如何：将现有实体附加到 DataServiceContext 中（WCF 数据服务）

如果实体已存在于数据服务中，使用 WCF 数据服务 客户端库可以将表示该实体的对象直接附加到 DataServiceContext 中，而不必首先执行查询。 有关更多信息，请参见更新数据服务（WCF 数据服务）。

本主题中的示例使用 Northwind 示例数据服务和自动生成的客户端数据服务类。 此服务和这些客户端数据类是在完成 WCF 数据服务快速入门时创建的。

示例

下面的示例演示如何创建一个现有 Customer 对象，该对象包含将保存到数据服务的更改。 该对象附加到上下文中，并调用 UpdateObject 方法将附加的对象标记为 Modified，然后再调用 SaveChanges 方法。

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

' Define an existing customer to attach, including the key.
Dim customer As Customer = _
    customer.CreateCustomer("ALFKI", "Alfreds Futterkiste")

' Set current property values.
customer.Address = "Obere Str. 57"
customer.City = "Berlin"
customer.PostalCode = "12209"
customer.Country = "Germany"

' Set property values to update.
customer.ContactName = "Peter Franken"
customer.ContactTitle = "Marketing Manager"
customer.Phone = "089-0877310"
customer.Fax = "089-0877451"

Try
    ' Attach the existing customer to the context and mark it as updated.
    context.AttachTo("Customers", customer)
    context.UpdateObject(customer)

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

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

// Define an existing customer to attach, including the key.
Customer customer = 
    Customer.CreateCustomer("ALFKI", "Alfreds Futterkiste");

// Set current property values.
customer.Address = "Obere Str. 57";
customer.City = "Berlin";
customer.PostalCode = "12209";
customer.Country = "Germany";

// Set property values to update.
customer.ContactName = "Peter Franken";
customer.ContactTitle = "Marketing Manager";
customer.Phone = "089-0877310";
customer.Fax = "089-0877451";

try
{
    // Attach the existing customer to the context and mark it as updated.
    context.AttachTo("Customers", customer);
    context.UpdateObject(customer);

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

请参阅

其他资源

数据客户端 (WCF Data Services)