Question

what is purpose of using the block​

Answer 1

Answer:

A block creates a const copy of any local variable that is referenced inside of its scope. Before blocks, whenever you wanted to call some code and have it call you back later, you would typically use delegates or NSNotificationCente

Explanation:

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Answer 2

Answer:

The using statement calls the Dispose method on the object in the correct way, and (when you use it as shown earlier) it also causes the object itself to go out of scope as soon as Dispose is called. Within the using block, the object is read-only and can't be modified or reassigned