string PaymentType;
SqlConnection con=new SqlConnection(ConString);
SqlCommand cmd=new SqlCommand("SELECT PaymentType FROM TableName WHERE ID =1", con);
con.open();
PaymentType=cmd.ExecuteScalar().ToString();
if(PaymentType=="FullPayment")
{
chkFullPayment.Checked=true;
}
else if(PaymentType=="EMI")
{
chkEMI.Checked=true;
}