Q:

Are there multiple ways to group radio buttons in Windows Forms?

I have a few radio buttons in my form that should all be connected, but I want one of them in a separate container to group it specifically with some other related inputs. Here is the general look:

Is there a way to group the fourth radio button with the other 3 even though it is in its own group box?

A:

Fact that radio buttons are mutually exclusive only when they are within same parent. Being said that I can think of two options.

Let them be in same parent, handle the Paint event of the parent and draw yourself manually giving the impression that they are different groups.
You have to manually manage the mutual exclusion :(

RadioButtons are no magic, they just set the Checked property of other radio's to false behind the scenes.
private List<RadioButton> radioButtons = new List<RadioButton>();
//Populate this with radios interested, then call HookUpEvents and that should work

private void HookUpEvents()
{
    foreach(var radio in radioButtons)
    {
        radio.CheckedChanged -= PerformMutualExclusion;
        radio.CheckedChanged += PerformMutualExclusion;
    }
}

private void PerformMutualExclusion(object sender, EventArgs e)
{
    Radio senderRadio = (RadioButton)sender;
    if(!senderRadio.Checked)
    {
        return;
    }
    foreach(var radio in radioButtons)
    {
        if(radio == sender || !radio.Checked)
        {
            continue;
        }
        radio.Checked = false;
    }
}

