類比檔案拖拽到指定表單中。

如何類比檔案拖拽，這個問題得反過來分析：“如何接受檔案拖拽”？
分別要用到API：
  DragAcceptFiles()函數，令表單接受檔案拖拽的訊息
  WM_DROPFILES訊息檔案拖拽時接收

看來得向表單發送WM_DROPFILES訊息，發送訊息是SendMessage()函數
為節約時間我們要站在巨人的肩膀--搜尋
關鍵詞就基本確定為：“WM_DROPFILES SendMessage 類比檔案拖拽”
此處省略1000字

uses ShlObj;

function ExecDropFile( // 類比檔案拖拽
  AHandle: THandle; // 目標表單控制代碼
  AFileName: string // 檔案名稱
): Boolean; // 返回執行是否成功
var
  vDropFiles: TDropFiles;
  vProcessId: DWORD;
  vProcess: THandle;
  vPointer: PChar;
  vNumberOfBytesRead: Cardinal;
begin
  Result := False;
if not FileExists(AFileName) or not IsWindow(AHandle) then Exit;
  GetWindowThreadProcessId(AHandle, @vProcessId);
  vProcess := OpenProcess(PROCESS_VM_OPERATION or PROCESS_VM_READ or
    PROCESS_VM_WRITE, False, vProcessId);
try
    vPointer := VirtualAllocEx(vProcess, nil, 4096, MEM_RESERVE or MEM_COMMIT,
      PAGE_READWRITE);
try
      FillChar(vDropFiles, SizeOf(vDropFiles), 0);
      vDropFiles.pFiles := SizeOf(TDropFiles);
      WriteProcessMemory(vProcess, vPointer,
        @vDropFiles, SizeOf(vDropFiles), vNumberOfBytesRead);
      WriteProcessMemory(vProcess, vPointer + SizeOf(vDropFiles),
        PChar(AFileName), Length(AFileName) + 1, vNumberOfBytesRead);
      SendMessage(AHandle, WM_DROPFILES, Integer(vPointer), 0);
finally
      VirtualFreeEx(vProcess, vPointer, 0, MEM_RELEASE);
end;
finally
    CloseHandle(vProcess);
end;
  Result := True;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  ExecDropFile(FindWindow('Notepad', nil), 'c:/temp/temp.txt');
end;