Hi Joern,
You can tell the axes to display on the front chart wall - the following code shows how to achieve this with a simple bar chart:
NChart chart = nChartControl1.Charts[0];
NBarSeries bar = new NBarSeries();
bar.Values.Add(10);
bar.Values.Add(20);
bar.Values.Add(30);
chart.Series.Add(bar);
// transparent visible front wall
chart.Wall(ChartWallType.Front).Visible = true;
chart.Wall(ChartWallType.Front).FillStyle = new NColorFillStyle(Color.Transparent);
chart.Wall(ChartWallType.Front).BorderStyle.Width = new NLength(0);
// axis constline shows on the front wall only
NAxisConstLine constline = new NAxisConstLine();
constline.Value = 10;
constline.SetShowAtWall(ChartWallType.Back, false);
constline.SetShowAtWall(ChartWallType.Front, true);
chart.Axis(StandardAxis.PrimaryY).ConstLines.Add(constline);
Hope this helps - let us know if you have any questions or meet any problems.
Best Regards,
Nevron Support Team