Why Does Delphi Console Application Need Form For TSQLConnection To Work?

Question

I have a simple Console Application written using Delphi XE2.

program Project1;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils,
  Data.DBXMSSQL,
  Data.DB,
  Data.SqlExpr;

var
  myConnection: TSQLConnection;

begin
  try
    { TODO -oUser -cConsole Main : Insert code here }

    myConnection := TSQLConnection.Create(nil);
    myConnection.DriverName := 'MSSQL';
    myConnection.GetDriverFunc := 'getSQLDriverMSSQL';
    myConnection.LibraryName := 'dbxmss.dll';
    myConnection.VendorLib := 'sqlncli10.dll';
    myConnection.LoginPrompt := False;
    myConnection.Params.Clear;
    myConnection.Params.Add('drivername=MSSQL');
    myConnection.Params.Add('schemaoverride=%.dbo');
    myConnection.Params.Add('hostname=myserver');
    myConnection.Params.Add('database=mydb');
    myConnection.Params.Add('blobsize=1');
    myConnection.Params.Add('localcode=0000');
    myConnection.Params.Add('isolationlevel=ReadCommited');
    myConnection.Params.Add('os authentication=True');
    myConnection.Params.Add('prepare sql=False');
    myConnection.Connected := true;

    Writeln('myConnection Is connected');
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;

  Readln;
end.

When I run this, I get this error:

'DBX Error: Driver could not be properly initialized. Client library may be missing, not installed properly, of the wrong version, or the driver may be missing from the system path.'

If I add a VCL form to the application, I get the pop-up about enabling the "Visual Component Library" framework, which I say No to, and without doing anything else, now when I run the application I get 'myConnection Is connected'.

The only difference I can see is in the uses clause:

uses
  System.SysUtils,
  Data.DBXMSSQL,
  Data.DB,
  Data.SqlExpr,
  Unit1 in 'Unit1.pas' {Form1}

If I remove the Unit1 in 'Unit1.pas' {Form1} from the uses clause then the app fails to connect.

I do not want to include a form in my console application, so what is happening to the program when I do such that it works?

Answer 1

VCL internally calls CoInitialize during initialization (initializes the COM library on the current thread), but console application doesn't (the same problem occurs in worker thread requiring some COM-stuff).
Just make CoInitialize call in the beginning of program or in initialization section, and CoUninitialize after the work.

http://docwiki.embarcadero.com/RADStudio/Rio/en/DbExpress_Database_Specific_Information