What is an example of dramatic irony?

Consider The Ksatriya's Dharma (Dramatic Irony).

One of the essential ironies of the epic is the dharma of the ksatriya caste, which destines them to wage terrible war, existing in direct conflict with the more generalized dharma to commit no acts of violence. Krsna's recitation of the Bhagavad Gita to Arjuna during the early part of the war is a key portion of the text, not just for explaining this conflicted dharma, but for elucidating how a person is supposed to fulfill his dharma. While perhaps still ironic, Krsna explains that Arjuna's dharma is not in conflict with anything, since every man has his own dharma and must act in accordance with his dharma and no one else's. Only by acting with detachment when fulfilling his duties can Arjuna achieve his dharma.