update command of datagrid

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ASP.NET

Hi..!!!
update method is not working. when i click on edit it will allow to edit me that particular row but when i change the value & click on update the row is not getting affected

i tried a lot but not finding answer

code is as below
protected void Gdordermgmt_updatecmd(object sender, DataGridCommandEventArgs e)
{
TextBox txtamtrecieved = (TextBox)e.Item.FindControl("txtamtrecieved");
TextBox txtrevisedqtamt = (TextBox)e.Item.FindControl("txtrevisedqtamt");
TextBox tx = new TextBox();
tx = (TextBox)e.Item.Cells[8].Controls[0];
// cmd.CommandType = CommandType.Text;
cmd.CommandText ="Update tbl_mst_Order" +
" Set Revised_Quote_Amount= '" + txtrevisedqtamt.Text + "', Received_Amount='" + txtamtrecieved.Text + "'where Order_ID='"+ e.Item.ItemIndex +"'";
cmd.Parameters.Add(new SqlParameter("@txtrevisedqtamt", SqlDbType.Text));
cmd.Parameters["@txtrevisedqtamt"].Value = tx.Text;
cmd.ExecuteNonQuery();
Gdordermgmt.EditItemIndex = -1;
Gdordermgmt.DataBind();
}