Grouping Windows Forms Radiobuttons with different parent controls in C#

Question

I\'ve got a Windows Forms application in which I have a number of RadioButtons. These RadioButtons are placed within a FlowLayoutPanel which automatically arranges

Answer 1

Here is a little improvement over the first answer: create a RadioGroup class that encapsulates the grouping functionality and adds support for standard keyboard navigation (up/down keys) and makes tabbing work.

To use it, simply declare a RadioGroup member in your form and new it (after InitializeComponent()), passing all the radio buttons you want in the group in proper order.

public class RadioGroup
{
    List _radioButtons;

    public RadioGroup(params RadioButton[] radioButtons)
    {
        _radioButtons = new List(radioButtons);
        foreach (RadioButton radioButton in _radioButtons)
        {
            radioButton.TabStop = false;
            radioButton.KeyUp += new KeyEventHandler(radioButton_KeyUp);
            radioButton.CheckedChanged += new EventHandler(radioButton_CheckedChanged);
        }
        _radioButtons[0].TabStop = true;
    }

    void radioButton_KeyUp(object sender, KeyEventArgs e)
    {
        e.Handled = true;
        RadioButton radioButton = (RadioButton)sender;
        int index = _radioButtons.IndexOf(radioButton);

        if (e.KeyCode == Keys.Down)
        {
            index++;
            if (index >= _radioButtons.Count)
            {
                index = 0;
            }
            e.Handled = true;
        }
        else if (e.KeyCode == Keys.Up)
        {
            index--;
            if (index < 0)
            {
                index = _radioButtons.Count - 1;
            }
            e.Handled = true;
        }

        radioButton = _radioButtons[index];
        radioButton.Focus();
        radioButton.Select();
    }

    void radioButton_CheckedChanged(object sender, EventArgs e)
    {
        RadioButton currentRadioButton = (RadioButton)sender;

        if (currentRadioButton.Checked)
        {
            foreach (RadioButton radioButton in _radioButtons)
            {
                if (!radioButton.Equals(currentRadioButton))
                {
                    radioButton.Checked = false;
                }
            }
        }
    }
}

One caveat: the up/down keys won't work well with the existing RadioButton class because it already handles the up/down keys. One easy way to fix it to subclass RadioButton and turn off handling of up/down keys:

public class RadioButtonEx : RadioButton
{
    protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
    {
        if (keyData == Keys.Up || keyData == Keys.Down)
        {
            return true;
        }

        return base.ProcessCmdKey(ref msg, keyData);
    }
}