/// <summary>
/// 删除给定的任务
/// </summary>
/// <param name="task"></param>
public void Remove(Downloader task)
{
if (task.State!=DownloadState.NeedToPrepare ||
task.State!=DownloadState.paused ||
task.State!=DownloadState.Ended)
{
task.Pause();
}
using (locker.LockList(false))
{
downloads.Remove(task);
}
OnDownloadRemove(task);
}