Threadklasse mit Event aktualisiert nicht

[Blup]

vorgeschlagene Änderungen:

Delphi-Quellcode:

uses Classes, System.SyncObjs;

type
  TTestThread = class(TThread)
  private
    FTestProperty: string;
    FOnTest: TNotifyEvent;
    function GetTestProperty: string;
    procedure SetTestProperty(const AValue: string);
  protected
    FCS: TCriticalSection;
    procedure DoTest; virtual;
    procedure Execute; override;
  public
    constructor Create(CreateSuspended: Boolean);
    destructor Destroy; override;
    {kann aus einem anderen Thread gelesen und verändert werden}
    property TestProperty: string read GetTestProperty write SetTestProperty;
    {wird im Hauptthread aufgerufen (ermöglicht Zugriff auf die VCL)}
    property OnTest: TNotifyEvent read FOnTest write FOnTest;
  end;

implementation

procedure TTestThread.DoTest;
begin
  if Assigned(FOnTest) then  // ???: if not Assigned(FOnTest) then
    FOnTest(self);
end;

constructor TTestThread.Create(CreateSuspended: Boolean);
begin
  inherited Create(CreateSuspended);
  FTestProperty := 'default';
  FCS := TCriticalSection.Create;
end;

destructor TTestThread.Destroy;
begin
  FCS.Free;
  inherited;
end;

procedure TTestThread.Execute;
begin
  Synchronize(DoTest);
end;

function TTestThread.GetTestProperty: string;
begin
  FCS.Enter;
  try
    Result := FTestProperty;
  finally
    FCS.Leave;
  end;
end;

procedure TTestThread.SetTestProperty(const AValue: string);
begin
  FCS.Enter;
  try
    FTestProperty := AValue;
  finally
    FCS.Leave;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  FTest := TTestThread.Create(false);
  FTest.FreeOnTerminate := false;
  FTest.OnTest := MyTest;
  FTest.Resume;
  repeat
    CheckSynchronize(10);
  until FTest.Terminated;
  Caption := FTest.TestProperty;
  FTest.Free;
end;