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Detecting record lock in Paradox Table

Posted on 1998-11-30
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Last Modified: 2010-04-04
I am writing an multi-tier application using Delphi3 C/S version.  Is there any way I can detect from client A if a record has been locked due to editing by any other clients ?
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Question by:ray3898
4 Comments
 
LVL 1

Expert Comment

by:Gerhard100198
ID: 1348702
How about this:

Write a function that accepts the TDataSet name as a parameter and will return a TRUE value if the record is locked.

Then try and place the dataset in edit mode within a try except error handler. You could analyse the error in more detail to trap specifically for a situation where the record is locked. This function will however tell you if it is possible the allow the edit or not.

Example:

function IsLocked(TheDataSet: TDataSet): Boolean;
begin
   Result := False;
   try
     TheDataSet.Edit;
     TheDataSet.Cancel;
   Except
      Result := True;
   end;
end;

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LVL 27

Expert Comment

by:kretzschmar
ID: 1348703
hi ray3898,

a other method

procedure TForm1.Button1Click(Sender: TObject); {Or other EventMethod}
var IsLocked : Bool;
begin
 if dbiisrecordlocked(table1.handle,IsLocked) = DBIERR_NONE then
   if IsLocked then showmessage ('Record Locked');
end;

This requires the unit BDE in the uses clause of your unit.

meikl
0
 

Author Comment

by:ray3898
ID: 1348704
It seems to me that your method is reside on the client side rather than the application side (back-end).  Since both client A and client B would receive a copy of the actual data (table1.db) from the application server, so all locking are taken place on the local copy but not on the actual table (am I right ?)  Therefore, what I want is when client A want to edit a record, the program will check directly from the application server to determine the current status of the record. Is it possible to do it and how can I do it ?

Thank you
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LVL 3

Accepted Solution

by:
Ronald Buster earned 150 total points
ID: 1348705
I used to have the same problem, use the following statement,
just a code snippet from one of my sources

try

  ... whatever you want to do

except

   on E: EDBEngineError do

       begin

           ... record is proberly locked

       end;

end;

regards,

Cono
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