namespace ClassLibrary1;

interface

uses System.Runtime.InteropServices;

type
  [StructLayout(LayoutKind.Sequential)]
  TestRecord = public record
  public
    X: Int32;
    Y: Int32;
  end;

  TestClass = public class
  private
  protected
  public
      [UnmanagedExport('Test', CallingConvention.StdCall)]
      class procedure Test(out B: TestRecord);
      [UnmanagedExport('TestString', CallingConvention.StdCall)]
      class procedure TestString(out AString: WideString);
      [UnmanagedExport('TestStringRes', CallingConvention.StdCall)]
      class function TestStringRes: String;
  end;

implementation

class procedure TestClass.Test(out B: TestRecord);
begin
    B.X := 25;
    B.Y := -10;
end;

class procedure TestClass.TestString(out AString: WideString);
begin
    AString  := 'A wide string';
end;

class function TestClass.TestStringRes: String;
begin
    Result := 'A wider string';
end;

end.





unit untTest1;

interface

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

type
  TForm1 = class(TForm)
    btn1: TButton;
    procedure btn1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  TTestRecord = packed record
    X, Y: integer;
  end;

  procedure Test(out B: TTestRecord);stdcall; external 'ClassLibrary1.dll' name 'Test';
  procedure TestString(out AString: Widestring);stdcall; external 'ClassLibrary1.dll' name 'TestString';
  function TestStringRes: Widestring;stdcall; external 'ClassLibrary1.dll' name 'TestStringRes';

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.btn1Click(Sender: TObject);
var
  B: TTestRecord;
  AString: widestring;
begin
  Test(B);
  ShowMessage(IntToStr(B.X));
  ShowMessage(IntToStr(B.Y));
  ShowMessage(TestStringRes);
  SetLength(AString, 100);
  TestSTring(AString);
  ShowMessage(AString);
end;

end.