It should be free. Easily integrable with asp.net mvc. Extremely light-weight. It must sanitize the input.
for example, say if the user enters
hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
It must not break the formatting of the page!
if the user enters some nasty html or maybe any html at all or any javascript code, it should reject that.
It would be awesome if it did some sort of cuss-word checking too, but that is not a requirement. It can be jquery based.
Before you feel tempted to mark this question as duplicate, do check whether other questions are very old or something like that.