Examples of dramatic irony are:
-Readers are aware of Elinor's affection for Edward.
-Readers are aware of Brandon's affection for Marianne.
Dramatic irony is a situation when the audience or the readers know about the real situation but the characters are unaware of it.
Elinor and Marianne are sisters who are very different from each other. Elinor was the elder one and much sensible than Marianne. She didn't want that her family would walk into any problem because of her. Marianne, on the other hand, lacks the sense which Elinor is blessed with. Elinor and Edward possess equivalent thoughts and are attached to each other at the beginning of the novel. Marianne didn't find Brandon romantic enough and didn't find his company engaging but he had affection for her which is only known to the readers.