DLL Connection ?

Pass the connection object(Pointer) to the DLL

How?
And at design time I leave the connection property blank right? and then at runtime how do I tell the ADO object to use the connection object?

Ross

You don't have to leave it blank but on the create of the form or datamodule that holds the ADO connection object you can assign a connection string then pass the in your dll you pass the connection object you created to it. Or you can pass the connection string as a PChar and to the Dll.

I don't think that passing the connection string will work. I used a udl file and had the objects in the dll use the same udl as the connection object in the calling app. Still generated the error.

How do I pass the connection object to the dll? I tried passing it as a TADOConnection parameter, that did not work.

Ross

Make the dll an comserver that way you would be able to pass the connection object

I don't mean to sound stupid but I don't know how to make a DLL a comserver.
Thanks for your help.

Ross

I will give this another try
This is my test dll. I am attempting to pass the ado connection to the dll. It works fine in the dll it runs the query. But when it returns to the calling application it returns a access violation. The code for the calling application is below. You will notice that in that code there is a try except the except portion is not called.

library testing;

uses
  SysUtils,
  Classes,
  adodb,
  dialogs;

procedure AdminReport(DB : TADOConnection);
var Q : TADOQuery;
begin
  Q := TADOQuery.create(nil);
  try
    with q do
    begin
      Connection := DB;
      sql.add('select count(*) S from cells');
      open;
      if fieldbyname('s').value > 0 then
        showmessage('Ha')
      else
        showmessage('crap');
    end;
  finally
    freeandnil(Q);
  end;
end;

Exports
  AdminReport;
end.

Calling Application procedure

procedure TfrmMain.mniAdmitClick(Sender: TObject);
var
  LibHandle   : THandle;
  AdminReport : TAdminReport;
begin
  frmMain.hide;
  LibHandle := LoadLibrary('C:\Projects\Outcomes\Testing\testing.dll';
  try
    try
      if LibHandle = 0 then
        raise EDLLLoadError.Create('Unable to Load Admin Report');
      @AdminReport := GetProcAddress(LibHandle, 'AdminReport');
      if not (@AdminReport = nil) then
        AdminReport(dtmMain.adoMain)
      else
        RaiseLastWin32Error;
    finally
      FreeLibrary(LibHandle); // Unload the DLL.
    end;
  except
    showmessage('Help');
    raise;
  end;
end;//After this end I get an access violation!!!

Thank You
Ross

I changed the parameter DB to a var parameter so the DLL procedure now looks like
procedure AdminReport(var DB : TADOConnection);

Try running outside the delphi enviroment and see what happens

Same thing. I get the 'Ha' message like I should. Then a quick flash of the main form and nothing.

When I ran your could I got a Win 32 API Error

I figured it out!
The AdminReport variable I had delclared like so
  TAdminReport = procedure (AHandle: THandle; var DB: TADOConnection); stdcall;

it should have been like this
  TAdminReport = procedure (AHandle: THandle; var DB: TADOConnection);

The 'stdcall' made the difference. So I am not sure what to do with points for this question.

Thanks,
Ross

Keep them if you want not a big deal

I will reduce points to 75 and give you the answer for helping me.
Is that ok?