unit prj_test;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
   ADODB, StdCtrls;

type
  // Определение интерфейса
  IMQLADO = Interface(IInterface)
  ['{A821E663-27E2-462F-AD1C-96AA200117CE}']
  function OpenConnect(ServerName, DatabaseName:PWideChar):Pointer stdcall;
end;

type
  TMQLADO = Class(TInterfacedObject, IMQLADO)
  private
  public
    function OpenConnect(ServerName, DatabaseName:PWideChar):Pointer stdcall;
end;


type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
{
constructor TMQLADO.Create();
begin
 inherited;
end;
}

function TMQLADO.OpenConnect(ServerName, DatabaseName:PWideChar):Pointer stdcall;
var
 ADOConnection: TADOConnection;
var
  strerr: widestring;
begin
  try
    ADOConnection := TADOConnection.Create(nil);
    ADOConnection.LoginPrompt := false;
    ADOConnection.KeepConnection := false;
    if not ADOConnection.Connected then
     begin
      ADOConnection.Close;
      ADOConnection.ConnectionString := 'Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=' + DatabaseName + ';Data Source=' + ServerName + ';Use Procedure for Prepare=1;Auto Translate=True;Packet Size=4096;Use Encryption for Data=False;Tag with column collation when possible=False';
      ADOConnection.ConnectionTimeout := 30;
      ADOConnection.Connected := true;
      result := Pointer(ADOConnection);
     end;
  except
    on e: Exception do
    begin
      strerr := 'ERROR: ' + E.Message;
      result := NIL;
    end;

  end;
 end;
procedure TForm1.Button1Click(Sender: TObject);
var
  IMQL: IMQLADO;
  TMQL: TMQLADO;
begin
  TMQL.Create;
  IMQL := TMQL; // <- RUNTIME ERROR 
end;

end.

procedure TForm1.Button1Click(Sender: TObject);
var
  IMQL: IMQLADO;
  TMQL: TMQLADO;
begin
  TMQL := TMQLADO.Create;
  IMQL := TMQL;
  IMQL.OpenConnect('(local)', 'MT4');
end;

library ptr_mssql;
***
function GetMQLADO(): IMQLADO;
begin
  Result := TMQLADO.Create;
end;

exports

GetMQLADO;

begin

end.

procedure TForm1.Button3Click(Sender: TObject);
var
  IMQL: IMQLADO;
begin
 IMQL := GetMQLADO();
end;

***
function GetMQLADO(): IMQLADO; external 'ptr_mssql';
***
procedure TForm1.Button3Click(Sender: TObject);
var
  IMQL: IMQLADO;
begin
 IMQL := GetMQLADO();
end;

unit prj_test;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
   ADODB, StdCtrls, MQLADO, InterfaceMSSQL, ShareMem;
***
var
  Form1: TForm1;
  HandleConnect: Pointer;
  HandleQuery: Pointer;
  IMQL: IMQLADO;

function GetMQLADO(): IMQLADO; external 'ptr_mssql';

procedure TForm1.Button3Click(Sender: TObject);
begin
 IMQL := GetMQLADO();
 HandleConnect := IMQL.OpenConnect('(local)', 'MT4');
 IMQL.CloseConnect(HandleConnect);
end;