Selecting multiple sections on a chart in c#

Question

I am trying to make a simple WindowsFormAplication with data displayed in charts with type column.

Now, the idea is for the user to select a part of the chart, and for t

Answer 1

There can only be one range selected at any time.

So you need to ..

• ..collect the ranges and
• ..probably also collect the selected DataPoints.
• Finally you also need to decide on a UI to clear the selections.

An simple way to display several selections, very similar to the cursor selection is adding Striplines..:

Here is the code for the above result; note that it assumes that your values will fit in a float and abuses the SizeF structure to store the start and end values of the selections. If you want to be more precise you can replace it with a Tuple..:

First three class level variables to hold the data, the ongoing selection, the list of ranges and a list of DataPoint indices:

SizeF curRange = SizeF.Empty;
List ranges = new List();
List selectedIndices = new List();

This event holds the new selections in the param e, so we can store them:

private void chart1_SelectionRangeChanging(object sender, CursorEventArgs e)
{
    curRange = new SizeF((float)e.NewSelectionStart, (float)e.NewSelectionEnd);
}

Now the selection process is done; the selection data is lost by now, but we have stored them. So we can add the new range, collect the newly selected DataPoint indices and finally create and display a new StripLine:

private void chart1_SelectionRangeChanged(object sender, CursorEventArgs e)
{
    ranges.Add(curRange);
    selectedIndices.Union(collectDataPoints(chart1.Series[0], 
                          curRange.Width, curRange.Height))
                   .Distinct();

    StripLine sl = new StripLine();
    sl.BackColor = Color.FromArgb(255, Color.LightSeaGreen);
    sl.IntervalOffset = Math.Min(curRange.Width, curRange.Height);
    sl.StripWidth = Math.Abs(curRange.Height - curRange.Width);
    chart1.ChartAreas[0].AxisX.StripLines.Add(sl);
}

This little routine should collect all DataPoint indices in a range:

List collectDataPoints(Series s, double min, double max)
{
    List hits = new List();
    for (int i = 0; i < s.Points.Count ; i++)
        if (s.Points[i].XValue >= min && s.Points[i].XValue <= max) hits.Add(i);
    return hits;
}

To clear the selection you clear the two lists, the StripLines collection, and the curRange structure.