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We can even have a strongly typed Previous Page property if we use a @ Previous Page directive.
For now, we will leave our destination page code almost as is.
Notice we have an Is Cross Page Post Back property we can evaluate to determine if the request arrived as a result of cross page post back.
A value of false means the Previous Page did a Server. It’s also interesting to note the behavior of the Previous Page property during a cross page post back.
A cross page postback all starts with by setting the Post Back Url property of the Button control.
We do not need to respond to the Click Event for this button.
Server side validation presents a problem for cross page post backs because our response will come from the destination web form instead of the original web form where the user failed validation. Validation controls will run server-side when a cross page post back occurs, and the destination page inspects the Previous Page. As we mentioned earlier, when we touch the Previous Page property the runtime loads and executes the Previous Page form, including the validation controls.
We must check the Is Valid property of our previous page to make sure the page passed all validation tests.
However, we can’t always use validation on the client (some custom validation controls will only be able to validate servers-side), nor can we always trust the client to perform validation.An alternate approach, one that improves in 2.0, is to use Server. All of these options involve a new property on the Page class in 2.0: Previous Page.Previous Page represents the originating page in transfer and cross page post back operations.When the user clicks the button, client side Java Script will set our form’s action attribute to point to the destination page before posting.In the destination form, a client side post back will give us a non-null Previous Page property.
Transfer (improved in 2.0), and the new 2.0 cross page postback feature. I’m attempting a thorough examination of how to plan your attack in this post. This will simulate a client with scripting turned off (a scenario we should always be prepared to handle), and leads to some interesting behaviors later in some examples that follow.