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How to: Attach an Existing Entity to the DataServiceContext (WCF Data Services)

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Important

WCF Data Services has been deprecated and will no longer be available for download from the Microsoft Download Center. WCF Data Services supported earlier versions of the Microsoft OData (V1-V3) protocol only and has not been under active development. OData V1-V3 has been superseded by OData V4, which is an industry standard published by OASIS and ratified by ISO. OData V4 is supported through the OData V4 compliant core libraries available at Microsoft.OData.Core. Support documentation is available at OData.Net, and the OData V4 service libraries are available at Microsoft.AspNetCore.OData.

RESTier is the successor to WCF Data Services. RESTier helps you bootstrap a standardized, queryable, HTTP-based REST interface in minutes. Like WCF Data Services before it, Restier provides simple and straightforward ways to shape queries and intercept submissions before and after they hit the database. And like Web API + OData, you still have the flexibility to add your own custom queries and actions with techniques you're already familiar with.

When an entity already exists in a data service, the WCF Data Services client library enables you to attach an object that represents the entity directly to the DataServiceContext without first executing a query. For more information, see Updating the Data Service.

The example in this topic uses the Northwind sample data service and autogenerated client data service classes. This service and the client data classes are created when you complete the WCF Data Services quickstart.

Example

The following example shows how to create an existing Customer object that contains changes to be saved to the data service. The object is attached to the context and the UpdateObject method is called to mark the attached object as Modified before the SaveChanges method is called.

// 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);
}

' 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

See also