The most promint form of situational irony I find is how the point of madame loisel borrowing the necklace is to feel of a higher class but this causes her to become an even lower class than before the story. situational irony is irony in a situation where actions have an effect that is opposite from what was meant to happen.
verbal irony is a situation in which a person says one thing and means another, or uses words in the opposite meaning of what it is meant. A perfect example is when Mathilde doesn't really want her husband to give the invitation away, she is being sarcastic which is the most common form of verbal irony.
dramatic irony is irony that is inherent in a situation of drama and is aknowladged by the audience but not known by the characters in the situation. The best example of this that I find is when madame loisel tells madame forister she cannot replace the necklace because the clasp is being repaired where in reality it is lost.