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When you serialize entity objects such as Customers or Orders to a client over a network, those entities are detached from their data context.
The data context no longer tracks their changes or their associations with other objects.
On the middle tier, a new Data Context is created, the object is attached to the Data Context by using the Insert On Submit method, and the object is inserted when Submit Changes is called.
Exceptions, callbacks, and error conditions can be handled just as in any other Web service scenario. Public Sub Insert Order(By Val o As Order) Dim db As New Northwind Classes1Data Context(connection String) db. Insert On Submit(o) ' Exception handling not shown. Submit Changes() End Sub To delete an existing object from the database, the presentation tier calls the relevant method on the middle tier interface, and passes in its copy that includes original values of the object to be deleted.
Delete operations involve optimistic concurrency checks, and the object to be deleted must first be attached to the new data context.
In this example, the to indicate that the object does not have a timestamp (Row Version).
To insert a new object, the presentation tier just calls the relevant method on the middle tier interface, and passes in the new object to insert.
In some cases, it may be more efficient for the client to pass in only some values and have the middle tier construct the full object.
Executes the stored database procedure or scalar function associated with the specified CLR method.
This is not an issue as long as the clients are only reading the data.
It is also relatively simple to enable clients to add new rows to a database.
Use the Data Load Options object to change this default behavior.
For more information, see How to: Control How Much Related Data Is Retrieved.