Access CheckBoxField CheckBox in RowUpdating event of ASP.Net GridView

Specified argument was out of the range of valid values. Parameter name: index

after adding a check box to gridview when i am updating teh gridview i get above error

  cmd.Parameters.Add("@c_name", SqlDbType.VarChar).Value = ((TextBox)Gridview1Rows[0].Cells[1].Controls[0]).Text;
                cmd.Parameters.Add("@c_amt", SqlDbType.VarChar).Value = ((TextBox)Gridview1Rows[0].Cells[2].Controls[0]).Text;
                cmd.Parameters.Add("@c_type", SqlDbType.VarChar).Value = ((TextBox)Gridview1Rows[0].Cells[3].Controls[0]).Text;
                cmd.Parameters.Add("@check", SqlDbType.Bit).Value = ((CheckBox)Gridview1Rows[0].Cells[4].Controls[0]).Checked;

before to checkbox addition it was wroking fine