This is my code for the assigning the Data (I can only do it in that way):
SfDateTimeRangeNavigator rangeNavigator = new SfDateTimeRangeNavigator();
rangeNavigator.SetBinding(SfDateTimeRangeNavigator.ItemsSourceProperty, "Line0ExtendedData");
rangeNavigator.XBindingPath = "XValue";
rangeNavigator.YBindingPath = "YValue";