The appearance of a wedding dress or a bridal gown in a dream is generally considered an ill omen, though that depends on several aspects of the particular dream and the person's current psychology.
If you were wearing a wedding dress but you were not being at a wedding, you will soon meet with people you love.
If you where at a wedding and you were wearing the gown there will be trouble in the near future regarding your personal affairs.
If the bridal gown was dirty or in any other way not in pristine condition, you will have bad news from some people that you thought close to you.
There is also the psychological aspect of this dream, which might be at work at the unconscious level.
It could be possible that this dream manifests in such a form due to the fact that you are wishing for a wedding in real life!