Which Radio button in the group is checked?

user_90272 0
Viewed 342462

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;
     }
radio-button winforms .net c#
13 Answers

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;
user_13333690

In addition to the CheckedChangedEvent wiring one could use the Controls "Tag" property to distinguish between the radio buttons... an (spaghetti code) alternative would be the "TabIndex" property ;P

user_30719280

If you want to get the index of the selected radio button inside a control you can use this method:

public static int getCheckedRadioButton(Control c)
{
    int i;
    try
    {
        Control.ControlCollection cc = c.Controls;
        for (i = 0; i < cc.Count; i++)
        {
            RadioButton rb = cc[i] as RadioButton;
            if (rb.Checked)
            {
                return i;
            }
        }
    }
    catch
    {
        i = -1;
    }
    return i;
}

Example use:

int index = getCheckedRadioButton(panel1);

The code isn't that well tested, but it seems the index order is from left to right and from top to bottom, as when reading a text. If no radio button is found, the method returns -1.

Update: It turned out my first attempt didn't work if there's no radio button inside the control. I added a try and catch block to fix that, and the method now seems to work.

user_20119480

For developers using VB.NET


Private Function GetCheckedRadio(container) As RadioButton
    For Each control In container.Children
        Dim radio As RadioButton = TryCast(control, RadioButton)

        If radio IsNot Nothing AndAlso radio.IsChecked Then
            Return radio
        End If
    Next

    Return Nothing
End Function
Admin1

Yet another try - Using event lambda expressions

As form initializes a single event handler can be assigned to all controls of type RadioButton in a group box, and use .tabIndex or .tag property to identify what option is checked when it changes.

This way you can subscribe to any of the events of each radio button in one go

int priceOption = 0;
foreach (RadioButton rbtn in grp_PriceOpt.Controls.OfType<RadioButton>())
{
    rbtn.CheckedChanged += (o, e) =>
    {
        var button = (RadioButton)o;
        if (button.Checked)
        {
            priceOption = button.TabIndex;
        }
    };
}

As events are assigned to radio buttons only, no type checking of sender is implemented.

Also notice as we loop all buttons this could be a perfect moment to assign data properties, change text etc.

user_42999430
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