question tags with the imperative, affirmative and negative

Sometimes we say: Open the door, will you? Sometimes we say: Open the door, won't you? Are both correc
question tags with the imperative

Yes, both are correct and there is very little difference in meaning between the two. There is perhaps a slight suggestion that you might be expecting the answer to be no, if you use the ...won't you? question tag

By adding the tag to the imperative, open the door, you are softening the instruction and turning it into a request. Without it, it would sound very much like a command, so the tag has a similar effect to the addition of please
will you/won't you?q
The following examples are all variations on the basic …will you/won't you? theme and all show roughly the same degree of politeness

But note that the context of use is now the operating theatre and here the …won't you? tag would be inappropriate as the surgeon would never expect the answer to be no:h
Hand me the scalpel, please
Hand me the scalpel, will you please?h
Hand me the scalpel, would you?h
Hand me the scalpel, could you please?h
Could you hand me the scalpel? h
You can, of course, use …would you? and …could you? with your example, Gamil, in addition to …will you? and …won't you?, but note that with the imperative we cannot use …wouldn't you? or …couldn't you?.u
Note in the following example, the first suggestion is much more tentative and less confident than the second
Come back to my place for a coffee, won't you? ~ No, I'm sorry, I can't. I've got such an early start tomorrow that I have to go to bed now
<LI>
Let's go back to my place for coffee! ~ What a nice idea. A coffee and a brandy would round off that delicious meal nicely