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Counting Users logged into Access DataBase in Delphi

Posted on 2004-03-27
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Last Modified: 2010-08-05
Hi. I have converted some BDE files (Paradox) into an Access MDB and I used to have a procedure which counted the number of users logged into an application
by cloning cursors and using the BDE function "Check(DbiIsRecordLocked(Table.Handle, Locked))". This always worked great when users logged in and out, even if users crashed their OS.
I have searched about and came up with the code from Microsoft which uses OpenSchema with a SchemID which seems to not work (which I modified below).
I also checked some code which reads the LDB file, which I also have problems with as it is difficult to read this file, and anyway I dont feel its safe.

Anyone done this in Delphi already?

My test is like this so far (trying to load details into a memo), I guess I must not be understanding something :-))
I have 4 objects on a form: ADOconnection, ADOTable and a Tmemo and a Tbutton...

procedure TForm1.Button1Click(Sender: TObject);
const  SchemaID=  '{947bb102-5d43-11d1-bdbf-00c04fb92675}';
  var  Schema: TSchemaInfo;  Restrictions: OleVariant;
begin
  Schema:= siProviderSpecific;
  Restrictions:= 0; // not sure about this?
try  with ADOConn do begin
       Connected:= True;
       OpenSchema(Schema, Restrictions, SchemaID, TADODataSet(tblADO)); //crashes here so must be wrong
     end;
     with tblADO do begin
       First;
       while not EOF do begin
         AMemo.Lines.Add(Fields[0].Name);
         AMemo.Lines.Add(Fields[0].Value);
         Next;
       end;
    end;
except on e:exception do showmessage(e.message); end;
end;
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Question by:AutoProSoftwareUK
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5 Comments
 
LVL 19

Accepted Solution

by:
Melih SARICA earned 250 total points
ID: 10700433
Why not Creating a table for Checking Logs ?
   
Add user and Computer and type in a table when application starts.. and then when u close the applicatiion delete them from table...

or
this article would help u

http://support.microsoft.com/default.aspx?scid=kb;en-us;210331
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Author Comment

by:AutoProSoftwareUK
ID: 10719205
RE:Why not Creating a table for Checking Logs ?
What if the apllication crashes?
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LVL 19

Expert Comment

by:Melih SARICA
ID: 10719370
U should put a value to registry or an ini file... when application starts

if this is set when the application starts .. it means ur app was crashed
and u can delete the log in ur table

dont forget to add the workstation name to the log table ... cuz u must check log with username and workstation .. for multi user connections

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Author Comment

by:AutoProSoftwareUK
ID: 10719978
Good idea :-)
I had set a list of user names in a data file with a marker that he/she was logged in in the record, and
removed the marker when the app closed.
Problem was, if the app crashed the record was still tagged and then exceeded the "allowed user count" specified elsewhere.
Your solution will work I guess (not tried yet). Using this scenario, I assume that any file (ini, txt etc) local to each network
machine with a flag in it (e.g user name, y/n flag etc) will do, is that your idea?
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LVL 6

Expert Comment

by:FactorB
ID: 24565693
Hi AutoProSoftwareUK,
I used your code as a base for other question and we made it working,
if you are interested you can check:
http://www.experts-exchange.com/Programming/Languages/Pascal/Delphi/Q_24469369.html
Regards,
B.
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