Stop double call to function using radioButton CheckedChanged events?

Question

I have 3 radio buttons all held within a groupbox (so only 1 can be marked at a time). I've got my code working, but to be quicker on updating my label, I want to stop the function from being called twice when a new radioButton is selected.

For instance, in my code below, my default is rb1 and then I click rb2, the rb1 CheckedChanged Event fires and updates the label, then rb2's CheckedChanged Event fires and updates the label again (same value).

What would be the best way to add some extra criteria to where if the label has been updated once, then stop the function from being called again?

CODE:

private void rb1_CheckedChanged(object sender, EventArgs e)
    {
        if (cmbLetterType.Text.Length != 0)
        {
            updatePrintedCntLabel();
        }
    }

private void rb2_CheckedChanged(object sender, EventArgs e)
{
    if (cmbLetterType.Text.Length != 0)
    {
        updatePrintedCntLabel();
    }
}

private void rb3_CheckedChanged(object sender, EventArgs e)
{
    if (cmbLetterType.Text.Length != 0)
    {
        updatePrintedCntLabel();
    }
}

EDIT: To clarify, this is a C# Winforms application I'm doing this in.

score 4 · Answer 1 · answered Dec 11 '13 at 17:18

Consider this

public class Form1 : Form 
{


    public Form1()
    {
        rb1.CheckedChanged += rb_CheckedChanged;
        rb2.CheckedChanged += rb_CheckedChanged;
        rb3.CheckedChanged += rb_CheckedChanged;
    } 

    private void rb_CheckedChanged(object sender, EventArgs e)
    {

        if (!((Radiobutton)sender).Checked) return;

        if (cmbLetterType.Text.Length != 0)
        {
            updatePrintedCntLabel();
        }

    }
}

score 2 · Accepted Answer · answered Dec 11 '13 at 15:25

2

Change your condition to:

if (cmbLetterType.Text.Length != 0 && rb1.Checked)

Do this for the other 2 handlers as well (using rb2.Checked and rb3.Checked) and each one will only fire when it's the one that's become checked, not unchecked.

answered Dec 11 '13 at 15:25

Baldrick

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See, that's the weird thing. Originally I tried that. I have tested and confirmed that by the time rb1's checkedChanged event fires, it's value has already changed to false. Thus, checking it for checked and my combobox length in the checkedChanged event will never evaluate fully given the conditions. – Analytic Lunatic Dec 11 '13 at 15:29
1

Does the newly checked item's event handler not still work correctly in this case? Your desired code should still run once. – Baldrick Dec 11 '13 at 15:34
Ah, you're right. Seems during my testing I was getting a bit flustered over all the different criteria and when walking through my breakpoints checking this issue, I had not yet set the value of cmbLetterType. Thanks! – Analytic Lunatic Dec 11 '13 at 15:37

paparazzo · Answer 3 · 2013-12-11T15:34:41.033

The events are doing what are telling them to do

If you don't want to update the Label twice then don't
Simple, if the value did not change then don't update
Save the value and test for change

Why do you have three identical event handlers?
You can wire multiple events to the same handler.

Even if you use the approach from Baldrick you can get the button from sender.

Late tag on WinForm but still can use the same approach ( if (labelVal = value) return; )
In general use public properties

private string labelVal = string.empty;

public string LabelVal
{
    get { return labelVal; } 
    set
    { 
        if (labelVal = value) return;
        labelVal = value;
        NotifyPropertyChanged("LableVal");
    }
}

Stop double call to function using radioButton CheckedChanged events?

3 Answers3