Dll 的参数传递问题。帮帮忙！(100分)

unit TestUnit;

interface

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

type
  TFunc = function (MyInt:integer):integer 

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

var
  Form1: TForm1;

implementation
//  function ShowDllHello(ftStr:string):integer;stdcall;External'Dll_Hello.dll';

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
begin
  DoDllFunc;
end;

procedure TForm1.DoDllFunc;
var
  MyFunc:TFunc;
  MyHandle:THandle;
begin
  MyHandle:=LoadLibrary('Dll_Hello.dll');
  if MyHandle>32 then
  begin
    @MyFunc:=GetProcAddress(MyHandle,'ShowDllHello');
    if @MyFunc<>nil then
    begin
      showmessage(IntToStr(MyFunc(10)))
   //////////想不通，返回 为什么错！
    end;
    FreeLibrary(MyHandle);
  end;
end;

end.

library Dll_Hello;

uses
  SysUtils,Classes;

{$R *.RES}

function ShowDllHello(HelloStr:integer):integer;stdcall;
begin
  Result:=HelloStr * 99;
end;

exports
  ShowDllHello name 'ShowDllHello' 

begin
end.
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