Using checkboxes to delete lines off line graph

Question

I have a graph that has lines plotted on it from different lists. I have added several checkboxes and used if statements to check if the checkbox is clicked. Like so:

public Form1()
{           
    InitializeComponent();
    CreateGraph();
    this.Text = "HRM File Analyser";

    if (hrCheck.Checked)
    {
        drawHR();
        chart1.Update();
    }
    else if (!hrCheck.Checked)
    {
        chart1.Series["Heart Rate"].Points.Clear();
        chart1.Update();
    }
}

However, even after calling the update method nothing changes at all.

Anyone have any ideas?

Is the else condition functioning properly? Can you show the contents of drawHR()? — Bobby, Mar 03 '16 at 23:31
Also, are these checkboxes declared on this form? If so, you can't use their check-state in a conditional expression in the form's constructor. You would want to add a checked event handler for the checkboxes and put your conditional code in there. — Bobby, Mar 03 '16 at 23:42

score 0 · Answer 1 · edited May 23 '17 at 10:28

The first problem with the code you show us is that is seems to be interactive but everything (we see) really happens only once upon startup.

Instead you should code the CheckChanged event of the Checkbox! (You get to it by double-clicking the checkbox in the designer..)
Next I suggest not to clear away i.e. delete all the data. Instead simply disable the series. Now you can turn the series off or on..
The checkbox checking logic is also overblown; one check will be sufficient!

So the new and improved version would look like this:

public Form1()
{           
    InitializeComponent();
    CreateGraph();
    this.Text = "HRM File Analyser";
    hrCheck_CheckedChanged(null, null);   // set initial state
    ..
}

private void hrCheck_CheckedChanged(object sender, EventArgs e)
{
    chart1.Series["Heart Rate"].Enabled = hrCheck.Checked;
}

If you didn't create it by double-clicking, do not forget to hook up the hrCheck_CheckedChanged event!

Using checkboxes to delete lines off line graph

1 Answers1