// 将tasks保存到二进制文件中
public Boolean saveToFile(String file)
{try{if (tasks.Count==0){// 没任务就不存return false;}if (File.Exists(file)){// 原有文件删掉
            File.Delete(file);}// 写文件FileStream writeStream = new FileStream(file, FileMode.Create);BinaryWriter bw = new BinaryWriter(writeStream);foreach (Dld tt in tasks){bw.Write((String)tt.getID());// 以下强制类型转换并非必要，而是为了阅读时辨别类型bw.Write((String)tt.getFilename());bw.Write((String)tt.getUrl());bw.Write((long)tt.getRemoteFileSize());bw.Write((String)tt.getPercent());bw.Write((String)tt.getStatus());bw.Write((String)tt.getType());bw.Flush();}bw.Close();writeStream.Close();return true;}catch(Exception e){throw e;}
}// 从二进制文件中提取tasks
public Boolean loadFromFile(String file)
{try{if (File.Exists(file)==false){// 文件不存在直接返回return false;}// 读文件FileStream readStream = new FileStream(file, FileMode.Open);BinaryReader br = new BinaryReader(readStream);try{while(true){
// 读取过程正好是写入过程的逆序String id = br.ReadString();String filename = br.ReadString();String url = br.ReadString();long remoteFileSize = br.ReadInt64();String percent = br.ReadString();String status = br.ReadString();String type = br.ReadString();// 这个地方要根据类型判断Dld tnew = null;if (type.Equals("http")){tnew = new HttpDld(mainGui, id, filename, url, remoteFileSize, type);}else if (type.Equals("ftp")){tnew = new FtpDld(mainGui, id, filename, url, remoteFileSize, type);}tnew.setStatus(status);tnew.setPercent(percent);tasks.Add(tnew);};}catch(EndOfStreamException ex){// 读完会抛出这个异常，正常过程System.Console.WriteLine("文件" + file + "读取完毕,读取任务" + tasks.Count+"条.");}br.Close();readStream.Close();return true;}catch (Exception e){throw e;}
}