Ok it works when I set AutoRange to False and give values to MinValue and MaxValue for each axis.
But here comes my next problem - my real case is to emphasize on a group of points (an area) where the so called "interesting values" reside. I use this code:
MarkedZone zone = new MarkedZone();
zone.Background = new SolidColorBrush(Colors.Transparent);
zone.StartX = 2;
zone.EndX = 4;
zone.StartY = 2;
zone.EndY = 4;
zone.StrokeThickness = 1.0;
Everything works fine until I zoom the chart (snapshots are attached). My zone's bounds are outside the viewport (right-hand side), but I can still see the border which is confusing. The user could easily think that this is the end of the marked zone and never scroll right to see that it continues...
What about this problem?