What are the elements of equitable estoppel?

"The elements of equitable estoppel are: (1) the party to be estopped must be apprised of the facts; (2) that party must intend that his or her conduct be acted on, or must so act that the party asserting the estoppel had a right to believe it was so intended; (3) the party asserting the estoppel must be ignorant of the true state of facts; and (4) the party asserting the estoppel must reasonably rely on the conduct to his or her injury." Honig v. San Francisco Planning Dep't, 127 Cal.App.4th 520, 25 Cal.Rptr.3d 649, 655 (2005) (citing Mills, 134 Cal.Rptr.2d at 298 ).