How to check if the checkbox in gridview is checked or not?

protected void btnSubmit_Click(object sender, EventArgs e)
 {
           int iRow = 0;
           foreach (GridViewRow row in GridView1.Rows)
           {
              CheckBox chk = (CheckBox)row.FindControl("chkApproved");
              if (chk != null && chk.Checked)
              {
                Response.Write("Checkbox is checked (GridView Row No is "+ iRow.toString() +").");
              }
              iRow = iRow + 1;                                  
           }
  }