How to insert data in sql server through asp.net using c# and also using check Box for a particular value insert in table

protected void btn_submit_Click(object sender, EventArgs e)
{
    if (chk_checkedbox.Checked == true)
    {
        SqlCommand sqlcom;
        int id = 1;
        sqlcon.Open();
        sqlcom = new SqlCommand("Select columname from tablename", sqlcon);
        id = Convert.ToInt16 (sqlcom.ExecuteScalar());
        sqlcon.Close();
    }
    else
    {
        SqlCommand sqlcm;
        int  id =0;
        sqlcon.Open();
        sqlcm = new SqlCommand("Select columname from tablename", sqlcon);
        id = Convert.ToInt16 (sqlcm.ExecuteScalar());
        sqlcon.Close();
    }

    SqlCommand sqlcom;
    sqlcon.Open();
    sqlcom = new SqlCommand("insert into tablename values('"+id+"')", sqlcon);
    sqlcom.ExecuteNonQuery();
    sqlcom.Dispose();
    sqlcon.Close();
}