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Which Radio button in the group is checked?


Question

Using WinForms; Is there a better way to find the checked RadioButton for a group? It seems to me that the code below should not be necessary. When you check a different RadioButton then it knows which one to uncheck… so it should know which is checked. How do I pull that information without doing a lot of if statements (or a switch).

     RadioButton rb = null;

     if (m_RadioButton1.Checked == true)
     {
        rb = m_RadioButton1;
     }
     else if (m_RadioButton2.Checked == true)
     {
        rb = m_RadioButton2;
     }
     else if (m_RadioButton3.Checked == true)
     {
        rb = m_RadioButton3;
     }
2009/11/25
1
118
11/25/2009 4:51:14 PM

Accepted Answer

You could use LINQ:

var checkedButton = container.Controls.OfType<RadioButton>()
                                      .FirstOrDefault(r => r.Checked);

Note that this requires that all of the radio buttons be directly in the same container (eg, Panel or Form), and that there is only one group in the container. If that is not the case, you could make List<RadioButton>s in your constructor for each group, then write list.FirstOrDefault(r => r.Checked).

2009/11/25
219
11/25/2009 4:02:46 PM

You can wire the CheckedEvents of all the buttons against one handler. There you can easily get the correct Checkbox.

// Wire all events into this.
private void AllCheckBoxes_CheckedChanged(Object sender, EventArgs e) {
    // Check of the raiser of the event is a checked Checkbox.
    // Of course we also need to to cast it first.
    if (((RadioButton)sender).Checked) {
        // This is the correct control.
        RadioButton rb = (RadioButton)sender;
    }
}
2013/04/18

For those without LINQ:

RadioButton GetCheckedRadio(Control container)
{
    foreach (var control in container.Controls)
    {
        RadioButton radio = control as RadioButton;

        if (radio != null && radio.Checked)
        {
            return radio;
        }
    }

    return null;
}
2009/11/25

The OP wanted to get the checked RadioButton BY GROUP. While @SLaks' answer is excellent, it doesn't really answer the OP's main question. To improve on @SLaks' answer, just take the LINQ one step further.

Here's an example from my own working code. Per normal WPF, my RadioButtons are contained in a Grid (named "myGrid") with a bunch of other types of controls. I have two different RadioButton groups in the Grid.

To get the checked RadioButton from a particular group:

List<RadioButton> radioButtons = myGrid.Children.OfType<RadioButton>().ToList();
RadioButton rbTarget = radioButtons
      .Where(r => r.GroupName == "GroupName" && r.IsChecked)
      .Single();

If your code has the possibility of no RadioButtons being checked, then use SingleOrDefault() (If I'm not using tri-state buttons, then I always set one button "IsChecked" as a default selection.)

2019/04/12

You can use the CheckedChanged event for all your RadioButtons. Sender will be the unchecked and checked RadioButtons.

2009/11/25

You can use an Extension method to iterate the RadioButton's Parent.Controls collection. This allows you to query other RadioButtons in the same scope. Using two extension methods, you can use the first determine whether any RadioButtons in the group are selected, then use the second to get the selection. The RadioButton Tag field can be used to hold an Enum to identify each RadioButton in the group:

    public static int GetRadioSelection(this RadioButton rb, int Default = -1) {
        foreach(Control c in  rb.Parent.Controls) {
            RadioButton r = c as RadioButton;
            if(r != null && r.Checked) return Int32.Parse((string)r.Tag);
        }
        return Default;
    }

    public static bool IsRadioSelected(this RadioButton rb) {
        foreach(Control c in  rb.Parent.Controls) {
            RadioButton r = c as RadioButton;
            if(r != null && r.Checked) return true;
        }
        return false;
    }

Here's a typical use pattern:

if(!MyRadioButton.IsRadioSelected()) {
   MessageBox.Show("No radio selected.");
   return;
}
int selection = MyRadioButton.GetRadioSelection;
2012/04/14

Source: https://stackoverflow.com/questions/1797907
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