I want to ask the user to input a password. As the password is sometimes needed in a different thread than the main thread where VCL runs, I tried to send a Message to the main window and ask for the password. Then the main window asks the user.

How I ask the user:

```
procedure TMainForm.WMGetPassword(var Msg: TMessage);
var
  Password: String;
begin
  if QueryPassword(Password) then // function QueryPassword(out Password: String): boolean;
  begin
    Password := Password + #0; // Add #0-Terminator
    Move(Password[1], Msg.wParam, Length(Password) * sizeOf(Char)); // Copy the String in my buffer
    Msg.Result := 1;
  end
  else
  begin
    Msg.Result := 0;
  end;
end;

```

How I ask the main window:

```
var
  PasswordBuffer: PChar;
  Password: String;
begin
  PasswordBuffer := AllocMem(100 * sizeof(Char));
  PasswordResult := SendMessage(MainFormHWND, WM_GetPassword, Integer(PasswordBuffer), 0);
  Result := (PasswordResult <> -1);
  if not Result then
    Exit;

  SetString(Password, PasswordBuffer, 100);
  ShowMessage(Password);
end;

```

But `Password` and `PasswordBuffer` are empty afterwards. What am I doing wrong?