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dynamic connection string

Posted on 2004-09-22
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Last Modified: 2012-05-05
hello friends mine, today i have a simple question....

im working with a control TADOConnection, since now i was working with a static connectionstring,
but now, my aplication requires to be able to change the path from the application...just for make it configurable :) ....
so  i  have this code


procedure Tfrm_tmp.FormCreate(Sender: TObject);
begin
  try
    dbpath:='D:\bd_pd.mdb';
    conexion.ConnectionString:='Provider=MSDASQL.1;Persist Security Info=False;Extended Properties="DSN=MS       Access Database;DBQ='+dbpath+';DefaultDir=C:;DriverId=25;FIL=MS Access;MaxBufferSize=2048;PageTimeout=5;UID=admin;";Initial Catalog='+dbpath;
 except
 end;
end;

Where frm_tmp is the main form ....
the wrong is when i try to catch the error when the path isnt found... because a lot of forms depends of the connectionstring and those forms were created at the beging of application

 



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Question by:BaTy_GiRl
7 Comments
 
LVL 13

Expert Comment

by:BlackTigerX
Comment Utility
don't put that code in the OnCreate event of your form, but instead put it in the "Start" button OnClick event of your program, where it actually goes and uses that database
by doing it this way, you can change the configuration without having to close the program, just Stop the program, fix your configuration, Start, and you are ready to go, if it fails, then the "start" process fails, and you don't let the program continue

the other thing is, don't hardCode values, read them at least from an .ini file
for that, you can use something like this (put IniFiles in your uses clause)

  with TIniFile.Create(ChangeFileExt(Application.ExeName, '.ini')) do
  try
    dbPath:=ReadString('DB', 'DBPath', 'd:\db_pd.mdb');
  finally
    Free
  end
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Accepted Solution

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BlackTigerX earned 50 total points
Comment Utility
if you don't have a "Start" kind of thing, then if the other forms have datasets pointing to This connection, check to see if the connection if Active before opening any of the other forms where requested by the user, if is not active, then try to activate it at that point

The thing is, if you want to use dinamyc connection string, it doesn't make much difference if you only create it in the OnCreate event of your form, is not really very dinamyc, is is "TRULY" dinamic, if you create it ONLY when you need it
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Author Comment

by:BaTy_GiRl
Comment Utility
do you mean in the second option that i use a file to specify the path?
i`m getting that information from windows registry and i thing is surely

about the first option
>put it in the "Start" button OnClick event of your program, where it actually goes and uses that database

well the problem is that i have like 35 forms calling anothers and almost all of them uses the database

:( thanks
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Author Comment

by:BaTy_GiRl
Comment Utility
im agree with you  at this point
> OnCreate event of your form, is not really very dinamyc, is is "TRULY" dinamic, if you create it ONLY when you need it

let me try with that idea....and i will tell you what did happen= )
thanks


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LVL 12

Expert Comment

by:Ivanov_G
Comment Utility
if FileExists(dbpath) then ...
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LVL 22

Expert Comment

by:Ferruccio Accalai
Comment Utility
--> well the problem is that i have like 35 forms calling anothers and almost all of them uses the database
In this case i'd use simply the OnBeforeConnect event and check there if dbPath exists
This way you don't need to put a check somewhere, 'cause every time any form try to open the connection the event is fired.

so something like

procedure TForm1.ADOConnection1BeforeConnect(Sender: TObject);
begin
If not FileExists(dbpath) then
 begin
     // SHowMessage('Path Not Found'); or you can use an opendialog or something else to force an existent path
      //Abort;  If you want to stop the connection
   end;
   conexion.ConnectionString:='Provider=MSDASQL.1;Persist Security Info=False;Extended Properties="DSN=MS       Access Database;DBQ='+dbpath+';DefaultDir=C:;DriverId=25;FIL=MS Access;MaxBufferSize=2048;PageTimeout=5;UID=admin;";Initial Catalog='+dbpath
end;

And i repeat this event is fired due to a call to conexion.connected := true or conexion.open, so from whereever is needed

F68 ;-)
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Author Comment

by:BaTy_GiRl
Comment Utility
it sems like very good idea Ferruccio68, i haven´t tried yet .....
but my program is working as  BlackTigerX told me, the connection string is in all forms
but i alwas tought that it was another way.
so thanks for your help me im going to accept the two answers

=) greetings

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