Smooth scroling in chart with datetime x axis

Question

I have this simple graph plotted in a chart. On the X-axis the values are DateTime values.

public partial class Form1 : Form
{

    List<double> valuelist = new List<double>();
    List<DateTime> timelist = new List<DateTime>();

    public Form1()
    {
        InitializeComponent();

        // fill the lists with values
        for (int i = 0; i < 2000; i++)
        {
            double value = Math.Sin(i/20.0);
            valuelist.Add(value);
            timelist.Add(DateTime.Now.AddMinutes(i + 2));
        }

        // add the Values to the chart
        for (int i = 0; i < valuelist.Count; i++)
        {
            this.chart1.Series[0].Points.AddXY(timelist[i], valuelist[i]);
        }

        this.chart1.ChartAreas[0].AxisX.LabelStyle.Format = "dd.MM-hh:mm";

    }

    private void Form1_Load(object sender, EventArgs e)
    {

        chart1.Series[0].XValueType = ChartValueType.DateTime;


        chart1.ChartAreas[0].AxisX.Maximum = timelist.Max().ToOADate();
        chart1.ChartAreas[0].AxisX.Minimum = timelist.Min().ToOADate();


        chart1.ChartAreas[0].CursorX.AutoScroll = true;
        chart1.ChartAreas[0].CursorY.AutoScroll = true;

        chart1.ChartAreas[0].CursorX.IsUserSelectionEnabled = true;
        chart1.ChartAreas[0].CursorY.IsUserSelectionEnabled = true;


        chart1.ChartAreas[0].AxisX.ScaleView.Zoomable = true;
        chart1.ChartAreas[0].AxisY.ScaleView.Zoomable = true;

        DateTime intervall = timelist.Min().AddHours(3);


        chart1.ChartAreas[0].AxisX.ScaleView.Zoom(chart1.ChartAreas[0].AxisX.Minimum, intervall.ToOADate());


        // disable zoom-reset button 
        chart1.ChartAreas[0].AxisX.ScrollBar.ButtonStyle = ScrollBarButtonStyles.SmallScroll;

        // set scrollbar small change to blockSize 
        chart1.ChartAreas[0].AxisX.ScaleView.SmallScrollSize = intervall.ToOADate();
    }

}

My problem is that I cannot get the scrollbar to move smoothly. When I plot only the Y-Values and use just double values for the AxisX.Maximum , AxisX.Minimum , AxisX.ScaleView.Zoom and for AxisX.ScaleView.SmallScrollSize it works like a charm. But as soon as I use DateTime for the X-Values I can only scroll in steps. Does someone know how to surpass this? I have the feeling that this piece of code is the obstacle:

// set scrollbar small change to blockSize (e.g. 100)
chart1.ChartAreas[0].AxisX.ScaleView.SmallScrollSize = intervall.ToOADate();

EDIT:

The Interval for the X-Axis is automatic, the range is set by the ZoomLevel of chart1.ChartAreas[0].AxisX.ScaleView.Zoom . Here is a picture:

EDIT 2:

The Values for the X-Axis are DateTime-Values simulating a sampling of 1 value every minute:

timelist.Add(DateTime.Now.AddMinutes(i + 2));

Because it is a lot of values I did not set an interval. The code is posted this way, so that it can be copied as it is and run right away to try it out.

Answer 1

You scrolling interval is wrong.

It should not be the start of your data but the step you want to go when scrolling.

Looks like you want to scroll by 3 hours?

Here is what you do:

chart1.ChartAreas[0].AxisX.ScaleView.SmallScrollSizeType = DateTimeIntervalType.Hours;
chart1.ChartAreas[0].AxisX.ScaleView.SmallScrollSize = 3;

If you wanted to use a DateTime.ToOADate double to achieve the same you need it to start at the first day of the DataTime data type ( 0 aka 'dawn of time' aka 1899-12-30 ) and then add 3 hours:

 DateTime interval = DateTime.FromOADate(0).AddHours(3);
 chart1.ChartAreas[0].AxisX.ScaleView.SmallScrollSizeType = DateTimeIntervalType.Number;
 chart1.ChartAreas[0].AxisX.ScaleView.SmallScrollSize = interval.ToOADate();

To allow dragging the lift smoothly this may work better than setting the SmallScrollSize :

chart1.ChartAreas[0].AxisX.ScaleView.SmallScrollMinSizeType  =DateTimeIntervalType.Minutes;
chart1.ChartAreas[0].AxisX.ScaleView.SmallScrollMinSize = 60;

Use your unit and numbers! This will only work if you don't set the SmallScrollMinSize .