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Trapping errors in try .. except

Posted on 2002-04-03
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Last Modified: 2010-04-04
Can I know the codes to trapping error returned and displaying appropriate messages?

I have this code :
  try
  if DataSet.Modified then
  begin
    if MessageDlg('Do you want to save the record', mtConfirmation, [mbYes, mbNo],0) = mrNo then
    begin
       DataSet.Cancel;
       SysUtils.Abort;
    end
  end;

  except
    ShowMessage ('Record already exist. (Datamodule) Please enter a different date.');
    DataSet.Cancel;
    SysUtils.Abort;
  end;
end;

Currently, if my answer is no, it will create a silent exception and the msg will be shown. I only want that message to be shown if the record already exist in the database. How can i check the error code returned and react accordingly? Thanks!
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Question by:irene79
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2 Comments
 
LVL 12

Expert Comment

by:Lee_Nover
ID: 6916910
in the except do

except
  on E: EUpdateError do begin
    case E.ErrorCode of
      xx:
    end;
  end;

from the help file : Note:     If ErrorCode is 0, use the OriginalException property, which provides access to the exception that was caught.

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LVL 10

Accepted Solution

by:
Jacco earned 200 total points
ID: 6917315
You could check for a Yes in stead of a No:

 if DataSet.Modified then
 begin
   if MessageDlg('Do you want to save the record', mtConfirmation, [mbYes, mbNo],0) = mrYes then
  try
    .... post the record ...
  except
    ShowMessage ('Record already exist. (Datamodule) Please enter a different date.');
    DataSet.Cancel;
    SysUtils.Abort;
  end;
 end;

Or you could move the try down a bit:

 if DataSet.Modified then
 begin
   if MessageDlg('Do you want to save the record', mtConfirmation, [mbYes, mbNo],0) = mrNo then
   begin
      DataSet.Cancel;
      SysUtils.Abort;
   end
 end;
 try

 except
   ShowMessage ('Record already exist. (Datamodule) Please enter a different date.');
   DataSet.Cancel;
   SysUtils.Abort;
 end;

Regards Jacco
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