Stackoverflow exception error

See more:

C#

I have created a checkBox inside a usercontrol. My usercontrol is in Form1. When i click on checkBox , it must make Form1 always on top. But (inside my usercontrol.cs) i get this error:

StackOverflowException was unhandled
An unhandled exception of type 'System.StackOverflowException' occurred in LinksPlayer.exe

at the start of this event:
private void checkBoxOnTop_CheckedChanged(object sender, EventArgs e)

What I have tried:

//inside usercontrol
        public event EventHandler checkBoxOnTophandleA;
        private void checkBoxOnTop_CheckedChanged(object sender, EventArgs e)
        {
            if (checkBoxOnTophandleA != null) checkBoxOnTop_CheckedChanged(null, null);
        }

//and in Form1
        private void Form1_Load(object sender, EventArgs e)
        {
            topMenu1.checkBoxOnTophandleA += new EventHandler(topMenu1_checkBoxOnTophandle);
        }
        void topMenu1_checkBoxOnTophandle(object sender, EventArgs e)
        {
            this.TopMost = false;
        }