User kokos answered the wonderful Hidden Features of C# question by mentioning the using keyword. Can you elaborate on that? What are the uses of using?
Not using by means that the technology used is incidental, and the focus is on the approach being shown to be feasible. Without more context it's impossible to say what the intended import of the sentence is and whether by would actually be better or not.
Update May 2018. As many noted in the comments that using SHA-2 does not add any security to a self-signed certificate. But I still recommend using it as a good habit of not using outdated / insecure cryptographic hash functions. Full explanation is available in Why is it fine for certificates above the end-entity certificate to be SHA-1 based?.
By using a joystick or a pointing device, an on-screen keyboard allows people with mobility impairments to type data. The second sentence states that the on-screen keyboard is the one that uses the joystick or pointing device to allow impaired people to type data.
Yes Yes. Either way, when the using block is exited (either by successful completion or by error) it is closed. Although I think it would be better to organize like this because it's a lot easier to see what is going to happen, even for the new maintenance programmer who will support it later:
c# - in a "using" block is a SqlConnection closed on return or ...
Using calls Dispose() after the using -block is left, even if the code throws an exception. So you usually use using for classes that require cleaning up after them, like IO.