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Introducing Windows Azure- P16

Introducing Windows Azure- P16:The cloud platform is getting more and more attractive to the computing world. Today, service-oriented architecture (SOA) and aspect-oriented programming (AOP) techniques are widely used in enterprise solutions. A question an IT management team or a software development team may ask is, what is the next trend going to be? Cloud computing seems to be the right answer. | CHAPTER 2 ACCESS CLOUD TABLE STORAGE Deleting and Updating an Entity in a Single Cloud Data Storage Table Below are some concepts we should be aware of before we move to the exercise for deleting and updating data from cloud table storage. Essentially the class DataServiceContext plays a core role for all cloud table storage I O including the data retrieving action we have been using so far. If you go back to look at the project we created the base class of AddressTableContext is in a hierarchical relationship with DataServiceContext you can trace down like this AddressTableContext TableContext TableStorageDataServiceContext DataServiceContext. For each entity table in Azure cloud table storage there is an internal property called tracked that is assigned when a table is created. This is for the DataServiceContext to track the concurrency of the data table. The options for the value for this property are AppendOnly OverwriteChanges PreserveChanges and NoTracking. It is mandatory to assign a value to this property before the data I O actions such as updating inserting and deleting. How to determine the selection of this attribute should be analyzed on a case-by-case basis. The default setting is AppendOnly. This option means the server will not load the entity instance if the instance is already presented in the caches. When this option is selected and the entity is already tracked by a previous retrieve call the DataServiceContext object will not update. There is a chance the update will fail unless the application has very good information about the previous action s updating call. If the OverwriteChanges option is selected the DataServiceContext always loads the entity instance from the server and keeps it up to date and overwrites the previously tracked entity. If PreserveChanges is selected any property changes made to the entity object DataServiceContext are preserved. This should be a good choice when recovering from concurrency errors is required. Using .