In checkbox auto postback property is not working properly(C#)

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C#

I have a user home address.Once he fill the address details,Next time the same address will be retriew from that previous address.

I am using the checkbox for retriew the same address by using auto postback property is true.But it is not working.What can i do?

What I have tried:

protected void chkSameAddress_CheckedChanged(object sender, EventArgs e)
        {
            
                if (chkSameAddress.Checked)
                {
                    txtGuardianStreet.Text = txtstreet.Text;
                    txtGuardianCity.Text = txtCity.Text;
                    txtGuardianZip.Text = txtZip.Text;
                    txtGuardianCountry.Text = txtCountry.Text;
                }           
            
        }