Random x and y position

Only thing i want is to pick a random X position and random Y position

Random x = new Random(255); Random y = new Random(255); int xp = x.Next(0, 255); int yp = y.Next(0,255);

Error:  CS0236  A field initializer cannot reference the non-static field, method, or property 'Protivnik.x'

Error: CS0236   A field initializer cannot reference the non-static field, method, or property 'Protivnik.y'

Can anyone explain me why is this happening?