f = x^2 - 2 x y + 2 y

ContourPlot[f, {x, 0, 3}, {y, 0, 2}, Contours ->  Table[n/2, {n, 0, 18}], AspectRatio -> Automatic, ContourShading ->Automatic, ContourStyle->Black, ContourStyle->Black,  PlotPoints -> 100,  PerformanceGoal->"Quality"]

Plot3D[f, {x, 0, 3}, {y, 0, 2}, PlotRange -> All,Boxed -> True,  PlotPoints -> 100, BoxRatios -> {3, 2, 2}]