在DLL中调用组件的小例子

前几天CSDN中的一个朋友询问在DLL中访问窗体中的组件的问题，偶对DLL也不熟，也没有搞懂，昨天他对我说问题解决了,我借其小结一下，让自己印像深刻:
在DLL中访问组件时要类似这样进行判断:
if panl.Controls[i].ClassNameIS('TEDIT') then
TEdit(panl.Controls[i]).Clear;
而不能用这样进行判断:
if panl.Controls[i] is TEDIT then
TEdit(panl.Controls[i]).Clear;
对于DLL的知识回顾如下：
DLL 在win16与win32中有很大区别，在win16中DLL中是一个全局即只他配一次地址当两个DLL访问同一个变量会有冲突，而在win32中则对于 每个实例分配一个独立的地址空间，这类似于COM了，呵，待我回家看看书再好好组织一下语言，现在把DLL创建的过程写一下：
主框架：
library DLL名称;
uses 相关的单元

library Project1;

定义过程或函数
procedure 过程名;stdcall;
begin
end;

exports
过程名 ---------这是让其它程序可以调用的关键
begin
end;

{ 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,
ExtCtrls,
StdCtrls,
Dialogs,
Controls;

procedure ClearPanelText(panl:Tpanel);stdcall;
var i:integer;
begin
showmessage(inttostr(panl.ControlCount));
for i:=0 to panl.ControlCount-1 do
begin
if panl.Controls[i].ClassNameIS('TEDIT') then
TEdit(panl.Controls[i]).Clear;
if panl.Controls[i].ClassNameIS('TCombobox') then
TCombobox(panl.Controls[i]).Text:='';

end;
end;

function getsum(i: integer): integer;stdcall;
begin
result := i;
end;
{$R *.res}

exports
ClearPanelText,getsum;
begin
end.


调用的例子：
unit Unit1;

interface

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

type
TForm1 = class(TForm)
Button1: TButton;
Panel1: TPanel;
Edit1: TEdit;
Edit2: TEdit;
ComboBox1: TComboBox;
Button2: TButton;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
{ Private declarations }
procedure ClearText(panl:Tpanel);
public
{ Public declarations }
end;

var
Form1: TForm1;

procedure ClearPanelText(panl:Tpanel);stdcall;external'Project1.dll';
function getsum(i: integer):integer;stdcall;external'Project1.dll';
implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
i: integer;
begin
i := 200;
ClearPanelText(panel1);
//showmessage(inttostr(getsum(i)));
end;

procedure TForm1.ClearText(panl:Tpanel);
var i:integer;
begin
for i:=0 to panl.ControlCount-1 do
begin
if panl.Controls[i] is TEdit then
TEdit(panl.Controls[i]).Clear
else if panl.Controls[i]is TCombobox then
TCombobox(panl.Controls[i]).Text :='' ;
end;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
ClearText(panel1);
end;

end.