Why show natural in bar when note is sharped

MuseScore shouldn't display a sharp if it's not necessary and you are not required to add a sharp notation again if you want the second note to be sharp. Just try it. With MuseScore 2.0.3, create a score in C major for flute, press C, press Up arrow, you have a c sharp, press C again. You have two C sharp, the first one with the sharp, the second without it.

So how do you enter notes? and which version of MuseScore (and not MusicScore) are you using?

If you enter the notes sequentially then sharpening one notes causes the ones later in the bar to be sharpened also and does not add an additional sharp sign. If you have already entered the notes and then add a sharp to one of them near the beginning of the measure then it would be wrong for MuseScore to change all the other later notes since you have only changed one note.

From underquark's post:
If you have already entered the notes and then add a sharp to one of them near the beginning of the measure then it would be wrong for MuseScore to change all the other later notes since you have only changed one note.
and also...
From Brian Hannaway's post:
If the second note is required to remain sharp it is necessary to show the sharp notation again.

@Brian Hannaway:
Regarding the necessity of the second note remaining sharp in the measure...
Be advised that clicking the sharp symbol from the toolbar will add (e.g. force) the sharp symbol onto a note.
To avoid this (redundant) duplication of the sharp sign:
Instead of using the toolbar sharp sign, select the latter note and press the up arrow to raise its pitch. The sharp symbol will not be forced upon the latter note, as it carries over from the former note - i.e. the sharped pitch which displays earlier in the measure.

Regards.