原理分析:  
  
这需要用到 ShellAPI 单元的两个函数: DragAcceptFiles、DragQueryFile;  
  
用 DragAcceptFiles(窗口句柄, True); 以让窗口能够接受拖放;  
  
然后就等待 WM_DROPFILES 消息, 并用 DragQueryFile 函数处理消息参数, 从而获取信息.  
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代码文件:  
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unit Unit1;  
  
interface  
  
uses  
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  
  Dialogs, StdCtrls;  
  
type  
  TForm1 = class(TForm)  
    Memo1: TMemo;  
    procedure FormCreate(Sender: TObject);  
  protected  
    procedure WMDropFiles(var Message: TWMDropFiles); message WM_DROPFILES;  
  end;  
  
var  
  Form1: TForm1;  
  
implementation  
  
{$R *.dfm}  
  
uses ShellAPI;  
  
procedure TForm1.FormCreate(Sender: TObject);  
begin  
  DragAcceptFiles(Handle, True);  
end;  
  
procedure TForm1.WMDropFiles(var Message: TWMDropFiles);  
var  
  p: array[0..255] of Char;  
  i,count: Integer;  
begin  
  {先获取拖拽的文件总数}  
  count := DragQueryFile(message.Drop, $FFFFFFFF, nil, 0);  
  
  {分别获取文件名}  
  for i := 0 to count-1 do  
  begin  
    DragQueryFile(message.Drop, i, p, SizeOf(p));  
    Memo1.Lines.Add(p); {既然知道了文件名, 当然也可以随手打开它}  
  end;  
end;  
  
end.  
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窗体文件:  
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object Form1: TForm1  
  Left = 0  
  Top = 0  
  Caption = 'Form1'  
  ClientHeight = 154  
  ClientWidth = 261  
  Color = clBtnFace  
  Font.Charset = DEFAULT_CHARSET  
  Font.Color = clWindowText  
  Font.Height = -11  
  Font.Name = 'Tahoma'  
  Font.Style = []  
  OldCreateOrder = False  
  OnCreate = FormCreate  
  PixelsPerInch = 96  
  TextHeight = 13  
  object Memo1: TMemo  
    Left = 0  
    Top = 0  
    Width = 261  
    Height = 129  
    Align = alTop  
    Lines.Strings = (  
      'Memo1')  
    ScrollBars = ssBoth  
    TabOrder = 0  
  end  
end