library ProjectPnr;

{ Important note about DLL memory management: ShareMem must be the

  first unit in your library's USES clause AND your project's (select

  Project-View Source) USES clause if your DLL exports any procedures or

  functions that pass strings as parameters or function results. This

  applies to all strings passed to and from your DLL--even those that

  are nested in records and classes. ShareMem is the interface unit to

  the BORLNDMM.DLL shared memory manager, which must be deployed along

  with your DLL. To avoid using BORLNDMM.DLL, pass string information

  using PChar or ShortString parameters. }

uses

  SysUtils,

  Classes,

//再在Uses下声明一个函数：

function Add(a, b: integer):integer; // 函数功能 实现a，b相加

begin

   result := a + b;

end

exports add;  // 必须要有这句才能输出

begin

end.

function apnr(a,b: integer):integer; external 'test.dll';

procedure TForm2.Button1Click(Sender: TObject);

begin

 ShowMessage(add(1, 2));     //3

end;

//dll里函数

function add(a, b: integer): string;

begin

  result := IntToStr(a + b);

end;