I want to edit this code from the wolfram Documentation Center so that, the red curve comes as dashed lines and the black comes in solid. How to do that using ColorFunction?

Colour a curve red when its absolute coordinate is above 0:

Plot[ Sinc[x], {x, 0, 10}, ColorFunction -> Function[{x, y}, If[y > 0, Red, Black]], ColorFunctionScaling -> False, PlotStyle -> Thick]