任务似乎自动启动 [英] Tasks seem to start automatically

问题描述

我移植一个程序，有哪些是没有改善，当我将它移植，因为缓慢是因为访问数据库服务器（而不是次优code）条很长的加载时间。我提出了装载到与任务库现在的用户界面不会冻结，因为它加载一个独立的线程，但它的确让我对某事感到好奇：

I'm porting a program that had a very long loading time which was not improved at all when I ported it, as the slowness was because of accessing a db-server (and not sub-optimal code). I have moved the loading onto a separate thread with the Tasks library and now the UI doesn't freeze as it loads, but it did make me curious about something:

在 Task.Factory 对象有一个方法 StartNew 这是为了创建一个新任务，启动它，并返回对它的引用。这是有道理的，但似乎工作构造函数做同样的事情。

The Task.Factory object has a method StartNew which is supposed to create a new task, start it, and return a reference to it. This makes sense, but it seems that the Task constructor does the exact same thing.

当我做到以下几点：

Task catsFromDB = new Task(() => AddCategoriesFromDB(cts.Token), cts.Token);
catsFromDB.Start();

我得到一个错误 InvalidOperationException异常，我真的不明白。这似乎相信，我已经踢它关闭了。我还没有。

I get an error InvalidOperationException which I really don't understand. It seems to believe that I've kicked it off already. Which I haven't.

该erorr是：InvalidOperationException异常，开始可能不会被要求已完成的任务

The erorr is: "InvalidOperationException, Start may not be called on task that has completed"

错误是一些抵消code我在内。我需要尝试重新运行之前重置取消。

The error was some cancellation code I included. I needed to reset the cancellation before trying to run it again.

推荐答案

现在我觉得自己很蠢，但是这将是有益的，让从我的'绿色'学习别人（如新，经验不足）的错误：

Now I feel stupid, but it will be instructive to let others learn from my 'green' (as in "new", "inexperienced") error:

我需要有问题的操作要撤销并重新运行的，所以我已经实现，它总是得到这样的实际负荷前运行CancelLoad操作。事实证明，我忘了创建取消和等待后，一个新的令牌。

I needed the operation in question to be cancellable and re-runnable, so I had implemented a "CancelLoad" operation which always got run before doing the actual load. It turns out that I forgot to create a new Token after canceling and waiting.

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