Currently, there seems to be no convenient API for formatting data point elements. There is a CreatePointElement event, which however does not work properly.

To reproduce:

Setup the following RadChartView:

this.Chart.ShowLegend = true;
this.Chart.Series.Add(new LineSeries() { LegendTitle = "DDDD" });
this.Chart.ChartElement.LegendElement.Items[0].Element.BorderDashStyle = System.Drawing.Drawing2D.DashStyle.DashDotDot;


for (int i = 0; i < 10; i++)
{
    this.Chart.Series[0].DataPoints.Add(i);
}


You will see that although that you have changed the BorderDashStyle of the Element, the LineSerie will be drawn normally.

Currently RadChartView does not support null values.

RadChartView - DateTimeContinueAxis ignores the MaximumTicks property with some specific data points. 

Steps to reproduce:
Use the following points:
            points.Add(new CategoricalDataPoint(r.Next(0, 100), new DateTime(2007, 7, 24)));
            points.Add(new CategoricalDataPoint(r.Next(0, 100), new DateTime(2007, 10, 30)));
            points.Add(new CategoricalDataPoint(r.Next(0, 100), new DateTime(2008, 4, 29)));
            points.Add(new CategoricalDataPoint(r.Next(0, 100), new DateTime(2008, 10, 27)));
            points.Add(new CategoricalDataPoint(r.Next(0, 100), new DateTime(2009, 4, 1)));
            points.Add(new CategoricalDataPoint(r.Next(0, 100), new DateTime(2010, 6, 28)));
            points.Add(new CategoricalDataPoint(r.Next(0, 100), new DateTime(2010, 10, 7)));
            points.Add(new CategoricalDataPoint(r.Next(0, 100), new DateTime(2011, 4, 19)));
            points.Add(new CategoricalDataPoint(r.Next(0, 100), new DateTime(2011, 9, 27)));
            points.Add(new CategoricalDataPoint(r.Next(0, 100), new DateTime(2012, 1, 10)));
            points.Add(new CategoricalDataPoint(r.Next(0, 100), new DateTime(2012, 4, 11)));
            points.Add(new CategoricalDataPoint(r.Next(0, 100), new DateTime(2012, 10, 16)));

To reproduce: use the following code snippet
public Form1()
{
    InitializeComponent();

    ScatterLineSeries scatterSeries = new ScatterLineSeries();
    scatterSeries.DataPoints.Add(new ScatterDataPoint(15, 19));
    scatterSeries.DataPoints.Add(new ScatterDataPoint(18, 10));
    scatterSeries.DataPoints.Add(new ScatterDataPoint(13, 15));
    scatterSeries.DataPoints.Add(new ScatterDataPoint(10, 8));
    scatterSeries.DataPoints.Add(new ScatterDataPoint(5, 2));
    scatterSeries.PointSize = new SizeF(8, 8);
    this.radChartView1.Series.Add(scatterSeries);

    ScatterLineSeries scatterSeries2 = new ScatterLineSeries();
    scatterSeries2.DataPoints.Add(new ScatterDataPoint(2, 24));
    scatterSeries2.DataPoints.Add(new ScatterDataPoint(7, 12));
    scatterSeries2.DataPoints.Add(new ScatterDataPoint(15, 10));
    scatterSeries2.DataPoints.Add(new ScatterDataPoint(18, 22));
    scatterSeries2.DataPoints.Add(new ScatterDataPoint(20, 20));
    scatterSeries2.Shape = new RoundRectShape(1);
    scatterSeries2.PointSize = new SizeF(8, 8);
    this.radChartView1.Series.Add(scatterSeries2);
    
    ChartTooltipController toolTipController = new ChartTooltipController();
   
    radChartView1.Controllers.Add(toolTipController); 
}

Workaround: use custom renderer

public Form1()
{
    InitializeComponent();

    this.radChartView1.CreateRenderer += radChartView1_CreateRenderer;
}
private void radChartView1_CreateRenderer(object sender, ChartViewCreateRendererEventArgs e)
{
    e.Renderer = new CustomCartesianRenderer(e.Area as CartesianArea);
}

public class CustomCartesianRenderer : CartesianRenderer
{
    public CustomCartesianRenderer(CartesianArea area) : base(area)
    {
    }
    
    protected override void Initialize()
    {
        base.Initialize();

        for (int i = 0; i < this.DrawParts.Count; i++)
        {
            ScatterSeriesDrawPart scatterPart = this.DrawParts[i] as ScatterSeriesDrawPart;
            if (scatterPart != null)
            {
                this.DrawParts[i] = new CustomScatterSeriesDrawPart((ScatterLineSeries)scatterPart.Element, this);
            }
        }
    }
}

public class CustomScatterSeriesDrawPart : ScatterLineSeriesDrawPart
{
    public CustomScatterSeriesDrawPart(ScatterLineSeries series, IChartRenderer renderer) 
        : base(series, renderer)
    {
    }

    public override DataPoint HitTest(Point location)
    {
        for (int i = 0; i < this.Element.DataPoints.Count; i++)
        {
            RadRect slot = this.Element.DataPoints[i].LayoutSlot;
            float pointHalfWidth = this.Element.PointSize.Width / 2;
            float pointHalfHeight = this.Element.PointSize.Height / 2;

            RectangleF scatterBounds = new RectangleF((float)(this.OffsetX + slot.X - pointHalfWidth),
                (float)(this.OffsetY + slot.Y - pointHalfHeight), this.Element.PointSize.Width, this.Element.PointSize.Height);

            if (scatterBounds.Contains(location.X, location.Y))
            {
                return this.Element.DataPoints[i];
            }
        }

        return null;
    }
}

Add null value support for RadChartView

To reproduce: -add RadChartView and use the following code: this.radChartView1.AreaType = ChartAreaType.Pie; PieSeries series = new PieSeries(); series.DataPoints.Add(new PieDataPoint(50, "Germany")); series.DataPoints.Add(new PieDataPoint(70, "United States")); series.DataPoints.Add(new PieDataPoint(40, "France")); series.DataPoints.Add(new PieDataPoint(25, "United Kingdom")); series.ShowLabels = true; this.radChartView1.Series.Add(series);

Workaround: recreate the ChartDataPointElementController: this.radChartView1.AreaType = ChartAreaType.Pie; this.radChartView1.Controllers.RemoveAt(0); this.radChartView1.Controllers.Add(new ChartDataPointElementController()); PieSeries series = new PieSeries(); series.DataPoints.Add(new PieDataPoint(50, "Germany")); series.DataPoints.Add(new PieDataPoint(70, "United States")); series.DataPoints.Add(new PieDataPoint(40, "France")); series.DataPoints.Add(new PieDataPoint(25, "United Kingdom")); series.ShowLabels = true; this.radChartView1.Series.Add(series);

To reproduce:
Add Series and Axes to a RadChartView and a ChartPanZoomController. Zoom and pan a little, then clear all the series and axes and add new ones. Try to pan now.

The Step Line chart type is similar to the Line chart type, but it does not use the shortest distance to connect two data points. Instead, this chart type uses vertical and horizontal lines to connect the data points in a series forming a step-like progression.

RadChartView -  sometimes Property Builder of RadChartView is setting HorizontalAxis to be LinearAxis and to VerticalAxis to be DateTimeCategoricalAxis when you select "Linear & Date Time Categorical " which leads to incorrect work of PanZoom.

Workaround:
Use Smart Tag instead of Property Builder or swap the types of the axes in Design file.

Add print functionality

To reproduce:
-add RadChartView and use the following code:
public Form1()
{
    InitializeComponent();

    radChartView1.SelectionMode = ChartSelectionMode.MultipleDataPoints;
    MessageBox.Show(radChartView1.SelectionMode.ToString());
    radChartView1.SelectionMode = ChartSelectionMode.MultipleDataPoints;
    MessageBox.Show(radChartView1.SelectionMode.ToString());
}

To reproduce:
1.Add RadChartView
2.Set vertical axis to be LinearAxis
3.Add DataPoints with value with 14 or more digits. 
4.Set FormatLabel = {0:C} or {0:F0} 
5.Run project and will see that labels overlaps vertical axis.

Workaround: 
Use custom format provider 
this.radChartView1.Axes[1].LabelFormatProvider = new MyFormatProvider();

To reproduce:
Add a RadChartView and add some LineSeries and data points. Set the ShowTrackBall property to true. In some cases KeyNotFound exception occurs.

Workaround:
Use the following class:
public class MyController : ChartTrackballController
{
    protected override string GetTrackballText(List<DataPointInfo> points)
    {
        StringBuilder result = new StringBuilder("<html>");

        SortedDictionary<ChartSeries, List<DataPoint>> visiblePoints = new SortedDictionary<ChartSeries, List<DataPoint>>(new ChartSeriesComparer());

        foreach (DataPointInfo pointInfo in points)
        {
            if (visiblePoints.ContainsKey(pointInfo.Series))
            {
                visiblePoints[pointInfo.Series].Add(pointInfo.DataPoint);
            }
            else
            {
                visiblePoints.Add(pointInfo.Series, new List<DataPoint>() { pointInfo.DataPoint });
            }
        }

        int counter = 0;
        foreach (ChartSeries series in visiblePoints.Keys)
        {
            for (int i = 0; i < visiblePoints[series].Count; i++)
            {
                Color pointColor = this.GetColorForDataPoint(series, visiblePoints[series][i]);
                string color = string.Format("{0},{1},{2},{3}", pointColor.A, pointColor.R, pointColor.G, pointColor.B);
                result.AppendFormat("<color={0}>{1}", color, this.GetPointText(visiblePoints[series][i]));

                if (i < visiblePoints[series].Count)
                {
                    result.Append(" ");
                }
            }

            counter++;

            if (counter < visiblePoints.Keys.Count)
            {
                result.Append("\n");
            }
        }

        result.Append("</html>");

        return result.ToString();
    }

    class ChartSeriesComparer : IComparer<ChartSeries>
    {
        public ChartSeriesComparer()
        {
        }

        public int Compare(ChartSeries x, ChartSeries y)
        {
            if (!(x is IndicatorBase) && y is IndicatorBase)
            {
                return -1;
            }
            else if (x is IndicatorBase && !(y is IndicatorBase))
            {
                return 1;
            }

            return x.GetHashCode().CompareTo(y.GetHashCode());
        }
    }
}

Replace the old controller as follows:
for (int i = 0; i < this.radChartView1.Controllers.Count; i++)
{
    if (this.radChartView1.Controllers[i] is ChartTrackballController)
    {
        this.radChartView1.Controllers[i] = new MyController();
        break;
    }
}

Note that the controller must be replaced before any data is added to the chart

Use the code below and reduce the Form size to see the extra line:

  public Form1()
        {
            InitializeComponent();

            radChartView1.Parent = this;
            radChartView1.Dock = DockStyle.Fill;
            radChartView1.ShowLegend = true;

            radChartView1.ShowGrid = true;
            CartesianGrid grid = ((CartesianGrid)radChartView1.GetArea<CartesianArea>().Grid);
            grid.DrawVerticalFills = true;
            grid.AlternatingHorizontalColor = false;
            grid.AlternatingVerticalColor = false;
            grid.BackColor = Color.Red;
            grid.ForeColor = Color.Blue;
            grid.BorderDashStyle = System.Drawing.Drawing2D.DashStyle.Solid;

            DateTimeContinuousAxis horizontalAxis = new DateTimeContinuousAxis();
            horizontalAxis.MajorStepUnit = Telerik.Charting.TimeInterval.Day;
            horizontalAxis.MajorStep =2;
            horizontalAxis.LabelFormat = "{0:dd/MM/yyyy}";
            LinearAxis verticalAxis1 = new LinearAxis();
            verticalAxis1.AxisType = AxisType.Second;
            LinearAxis verticalAxis2 = new LinearAxis();
            verticalAxis2.AxisType = AxisType.Second;
            verticalAxis2.HorizontalLocation = AxisHorizontalLocation.Right;

            LineSeries line1 = new LineSeries();
            line1.HorizontalAxis = horizontalAxis;
            line1.VerticalAxis = verticalAxis1;

            LineSeries line2 = new LineSeries();
            line2.HorizontalAxis = horizontalAxis;
            line2.VerticalAxis = verticalAxis2;

            line1.DataPoints.Add(new CategoricalDataPoint(26d, DateTime.Now.AddDays(-6)));
            line1.DataPoints.Add(new CategoricalDataPoint(20d, DateTime.Now.AddDays(-5)));
            line1.DataPoints.Add(new CategoricalDataPoint(12d, DateTime.Now.AddDays(-4)));
            line1.DataPoints.Add(new CategoricalDataPoint(15d, DateTime.Now.AddDays(-2)));
            line1.DataPoints.Add(new CategoricalDataPoint(21d, DateTime.Now.AddDays(-1)));

            line2.DataPoints.Add(new CategoricalDataPoint(32d, DateTime.Now.AddDays(-6)));
            line2.DataPoints.Add(new CategoricalDataPoint(52d, DateTime.Now.AddDays(-4)));
            line2.DataPoints.Add(new CategoricalDataPoint(35d, DateTime.Now.AddDays(-3)));
            line2.DataPoints.Add(new CategoricalDataPoint(36d, DateTime.Now.AddDays(-2)));
            line2.DataPoints.Add(new CategoricalDataPoint(11d, DateTime.Now.AddDays(-1)));

            line1.LegendTitle = "line1";
            line2.LegendTitle = "line2";

            this.radChartView1.Series.Add(line1);
            this.radChartView1.Series.Add(line2);
        }

To reproduce:
this.chart.Controllers.Add(new ChartTrackballController());
this.chart.Dock = DockStyle.Fill;
this.chart.AreaType = ChartAreaType.Cartesian;
LineSeries lineSeries1 = new LineSeries();
lineSeries1.Name = "Line 1";

lineSeries1.DataPoints.Add(new CategoricalDataPoint(10, "1"));
lineSeries1.DataPoints.Add(new CategoricalDataPoint(4, "2"));
lineSeries1.DataPoints.Add(new CategoricalDataPoint(23, "3"));
lineSeries1.DataPoints.Add(new CategoricalDataPoint(11, "4"));
lineSeries1.DataPoints.Add(new CategoricalDataPoint(15, "5"));
lineSeries1.DataPoints.Add(new CategoricalDataPoint(10, "6"));
lineSeries1.DataPoints.Add(new CategoricalDataPoint(4, "7"));
lineSeries1.DataPoints.Add(new CategoricalDataPoint(7, "8"));
lineSeries1.DataPoints.Add(new CategoricalDataPoint(11, "9"));
lineSeries1.DataPoints.Add(new CategoricalDataPoint(15, "10"));
this.chart.Series.Add(lineSeries1);

LineSeries lineSeries2 = new LineSeries();
lineSeries2.Name = "Line 2";

lineSeries2.DataPoints.Add(new CategoricalDataPoint(6, "1"));
lineSeries2.DataPoints.Add(new CategoricalDataPoint(20, "2"));
lineSeries2.DataPoints.Add(new CategoricalDataPoint(7, "3"));
lineSeries2.DataPoints.Add(new CategoricalDataPoint(8, "4"));
lineSeries2.DataPoints.Add(new CategoricalDataPoint(4, "5"));
lineSeries2.DataPoints.Add(new CategoricalDataPoint(10, "6"));
lineSeries2.DataPoints.Add(new CategoricalDataPoint(24, "7"));
lineSeries2.DataPoints.Add(new CategoricalDataPoint(17, "8"));
lineSeries2.DataPoints.Add(new CategoricalDataPoint(18, "9"));
lineSeries2.DataPoints.Add(new CategoricalDataPoint(43, "10"));
this.chart.Series.Add(lineSeries2);
this.chart.ShowTrackBall = true;

For workaround, use this class:
public class MyTrackBallController : ChartTrackballController
{
    protected override string GetTrackballText(List<DataPointInfo> points)
    {
        StringBuilder result = new StringBuilder("<html>");

        SortedDictionary<Telerik.WinControls.UI.ChartSeries, List<DataPoint>> visiblePoints 
            = new SortedDictionary<Telerik.WinControls.UI.ChartSeries, List<DataPoint>>(new ChartSeriesComparer());
        
        foreach (DataPointInfo pointInfo in points)
        {
            if (visiblePoints.ContainsKey(pointInfo.Series))
            {
                visiblePoints[pointInfo.Series].Add(pointInfo.DataPoint);
            }
            else
            {
                visiblePoints.Add(pointInfo.Series, new List<DataPoint>() { pointInfo.DataPoint });
            }
        }
        
        int counter = 0;
        foreach (Telerik.WinControls.UI.ChartSeries series in visiblePoints.Keys)
        {
            for (int i = 0; i < visiblePoints[series].Count; i++)
            {
                Color pointColor = this.GetColorForDataPoint(series, visiblePoints[series][i]);
                string color = string.Format("{0},{1},{2},{3}", pointColor.A, pointColor.R, pointColor.G, pointColor.B);
                result.AppendFormat("<color={0}>{1}", color, this.GetPointText(visiblePoints[series][i]));
        
                if (i < visiblePoints[series].Count)
                {
                    result.Append(" ");
                }
            }
        
            counter++;
        
            if (counter < visiblePoints.Keys.Count)
            {
                result.Append("\n");
            }
        }
        
        result.Append("</html>");
        
        return result.ToString();
    }

    class ChartSeriesComparer : IComparer<Telerik.WinControls.UI.ChartSeries>
    {
        public int Compare(Telerik.WinControls.UI.ChartSeries x, Telerik.WinControls.UI.ChartSeries y)
        {
            if (!(x is IndicatorBase) && y is IndicatorBase)
            {
                return -1;
            }
            else if (x is IndicatorBase && !(y is IndicatorBase))
            {
                return 1;
            }

            if (x.Equals(y))
            {
                return 0;
            }

            return 1;
        }
    }

}

Add method to zoom by specified parameters

To reproduce: 
AddChartView();
            radChartView1.ShowGrid = true;

            CartesianGrid grid = ((CartesianGrid)radChartView1.GetArea<CartesianArea>().Grid);
            grid.DrawVerticalFills = true;
            grid.AlternatingHorizontalColor = false;
            grid.AlternatingVerticalColor = false;
            grid.BackColor = Color.Red;
            grid.ForeColor = Color.Blue;
            grid.BorderDashStyle = System.Drawing.Drawing2D.DashStyle.Solid;

Steps to reproduce:
1. Add a chart to a form.
2. Add any cartesian series
3. Set the LabelFitMode of the horizontal axis to Rotate.

You will see that labels have incorrect layout.