Why is there no event with a RadioButton click?

I have Radio Buttons on my web page with AutoPostBack="True" and I have event handler routines created in the code file difined for each one similar to the first one as follows:
    protected void RadioButton1_CheckedChanged(object sender, EventArgs e)
    {
        string mystring = RadioButton1.Text;
        Session["Office"] = mystring;
    }
But, I set a breakpoint within this event handler routine and it never breaks when I click the Radio Button.  I even tried adding the following OnClick definition to the control’s properties as follows: OnClick = "RadioButton1_CheckedChanged"
But, that did not work either.  What am I doing wrong?
 
Maurice