Nullreferenceexception when adding point to chart

Question

Create chart:

    private Chart mainChart;
    private void createChart()
    {
        mainChart = new Chart
        {
            Dock = DockStyle.Fill,
            Name = "chart1",
        };
        mainChart.ChartAreas.Add(new ChartArea());
        mainChart.Legends.Add(new Legend());

        mainChart.ChartAreas[0].AxisX.Minimum = 1;
        for (int i = 0; i < 32; i++)
        {
            mainChart.Series.Add(new Series
            {
                Name = "test" + i,
                LegendText = "Test " + (i + 1).ToString().PadLeft(2, '0'),
                ChartType = SeriesChartType.FastLine,
            });
        }
    }

Chart property:

public Chart chart
{
    get
    {
        return mainChart;
    }
    set
    {
        mainChart = value;
        Form activeChild = FormAlreadyLoaded("Child_Chart");
        if (activeChild != null)
        {
            Chart frmchart = activeChild.Controls.Find("chart1", true).FirstOrDefault() as Chart;
            frmchart = mainChart;
        }
    }
}

FormAlreadyLoaded method:

private Form FormAlreadyLoaded(string formName)
{
    foreach (Form frm in this.MdiChildren)
        if (frm.Name.Equals(formName))
            return frm;
    return null;
}

Child_Chart is a simple form with this in the "Load" method:

MainForm parent = this.MdiParent as MainForm;
this.Controls.Add(parent.chart);

Add to chart (where the error happens)

chart.Series[i].Points.AddXY(value1,value2);

Exception text:

    System.NullReferenceException: Object reference not set to an instance of an object.
   at System.Windows.Forms.DataVisualization.Charting.Chart.get_Series()
   at Oasis.MainForm.<>c__DisplayClass13.<ProcessSerial>b__11() in MainForm.cs:line 355
   at System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(Object obj)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Windows.Forms.Control.InvokeMarshaledCallback(ThreadMethodEntry tme)
   at System.Windows.Forms.Control.InvokeMarshaledCallbacks()

More information:

createChart() is the first thing called in the load event of the main form.

The line of code that causes the error is inside a

this.BeginInvoke(new MethodInvoker(delegate()

in the DataRecieved event of a serialPort

Local values of 'mainChart' after the error appears i.imgur.com/LZSY3Iw.png

All this code works fine, until I close "Child_Chart".

score 0 · Answer 1 · answered Jan 29 '14 at 20:10

0

As Points property of series[i] is probably a non primitive type, you need to initialize it with its constructor using the 'new' keyword

answered Jan 29 '14 at 20:10

Tal

700
4
11

I added more information to the main post. – user2705775 Jan 29 '14 at 22:18

score 0 · Answer 2 · answered Jan 29 '14 at 21:18

0

Are you certain chart isn't what's null? I don't see where CreateChart() gets called, and I don't see anywhere else that private field mainChart is instantiated.

Aside from that, you need to break at the error and look to see which is the null reference. It could be chart, chart.Series, or chart.Series[i], and so on through the entire statement.

answered Jan 29 '14 at 21:18

mckrecker

45
1
2
8

I added more information to the main post. – user2705775 Jan 29 '14 at 22:18

Nullreferenceexception when adding point to chart

2 Answers2