I try to search for the answer but up to now I do not find the answer.

I'd say no. Necrons are not machines in the most technical sense of the word. They have no circuits or anything that haywire could disrupt, so I would assume they'd be unaffected.

I guess it would slightly confuse them. I imagine they'd stop a moment as the field washes over them, then turn to the originator of said field and blast him to bits for slightly inconvenience them.

I think necrons are probably advanced enough to not be affected by haywire but their is no solid rule saying so that I know of. Living metal is a whole different animal from regular tech and the self repair abilities would likely counteract most if not all of the effect.

I suppose it depends on how you define what Necrons are. Are they more machine, or more a living being? If the former, I'd say haywire definitely should have some effect. Perhaps not as strong as on regular tech because of some sort of shielding or backup systems, but "living metal" always sounded like nanomachines to me, and I don't see why those should not be affected by EMP in some way.

I think in the very least it should affect their weaponry/equipment to some degree. It might just disrupt a Gauss Rifle while it's creating its magnetic field right before firing and that's it.

For Necron Troops I would go with the standard haywire effects. For Elites and up, they may have some shielding or resistance that acts as 'haywire armor'.