Hello, Stephan,
In order to customize the chart that is drawn into
RadRangeSelector when it is associated with
RadChartView, the associated element should be accessed. The following code snippet demonstrates how this can be achieved and how to specify the label format for the horizontal axis:
public RadForm1()
{
InitializeComponent();
BarSeries series = new BarSeries();
series.DataPoints.Add(new CategoricalDataPoint(6, DateTime.Now));
series.DataPoints.Add(new CategoricalDataPoint(4, DateTime.Now.AddDays(1)));
series.DataPoints.Add(new CategoricalDataPoint(7, DateTime.Now.AddDays(2)));
series.DataPoints.Add(new CategoricalDataPoint(5, DateTime.Now.AddDays(3)));
this.radChartView1.Series.Add(series);
series.HorizontalAxis.LabelFormat = "{0:dd.MM}";
this.radRangeSelector1.AssociatedControl = this.radChartView1;
RangeSelectorViewElement chartElement = this.radRangeSelector1.RangeSelectorElement.AssociatedElement as RangeSelectorViewElement;
chartElement.SeriesInitialized += new SeriesInitializedEventHandler(chartElement_SeriesInitialized);
}
private void chartElement_SeriesInitialized(object sender, SeriesInitializedEventArgs e)
{
e.Series.HorizontalAxis.LabelFormat = "{0:dd.MM}";
}

The same approach can be followed if you want to customize the vertical axis as well:
private void chartElement_SeriesInitialized(object sender, SeriesInitializedEventArgs e)
{
e.Series.HorizontalAxis.LabelFormat = "{0:dd.MM}";
LinearAxis verticalAxis = e.Series.VerticalAxis as LinearAxis;
if (verticalAxis != null)
{
verticalAxis.Minimum = 0;
verticalAxis.Maximum = 100;
}
}

I hope this information helps. If you need any further assistance please don't hesitate to contact me.
Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik
Progress is here for your business, like always.
Read more about the measures we are taking to ensure business continuity and help fight the COVID-19 pandemic.
Our thoughts here at Progress are with those affected by the outbreak.