CheckBox in updatapanel...

I put 3 checkbox In to my updatepanel
the initial value for them is unChecked


chk1.Checked = false;
chk2.Checked = false;
chk3.Checked = false;


when I click Chk1 ( so chk1.Checked = true)


I use this code to collection these value
string CHKValue = "";

        for (int i = 1; i <=3; i++)
        {
            CheckBox CHK = new CheckBox();
            CHK.ID = "CHK" + i.ToString();

            if (CHK.Checked)
                 CHKValue += i.ToString();
        }

...