How can I get the events of 2 radionbuttons on 2 groupboxs in C#?

Question

Form1 has 2 groupboxs:

• groupbox1: radiobutton1 and radiobutton2
• groupbox2: radiobutton3 and radiobutton4

Code here:

public Form1()
{
    InitializeComponent();

    radioButton1.Checked = true; //create a default selection
    radioButton3.Checked = true; //create a default selection
}

Events here:

private void radioButton1_Click(object sender, EventArgs e)
{
    Console.WriteLine("radioButton1_Click");
}

private void radioButton3_Click(object sender, EventArgs e)
{
    Console.WriteLine("radioButton3_Click");
}

When the program runs, why do the radioButton1_Click event call only? How to call both radioButton1_Click and radioButton3_Click?