Eigen: random binary vector with t 1s

I want to compute K*es where K is an Eigen matrix (dimension pxp) and es is a px1 random binary vector with 1s.

For example if p=5 and t=2 a possible es is [1,0,1,0,0]' or [0,0,1,1,0]' and so on...

How do I easily generate es with Eigen?