[英]How can I use delegates to pass methods in a thread wrapper class?
I'm currently self-teaching myself C# and I'm a bit new at programming so apologies in advance if this is covered in another topic (I tried searching). 我目前正在自学C#,我在编程方面有点新意,如果在另一个主题(我试过搜索)中有所涉及,请提前道歉。
I've been trying to make a generic worker / thread class that takes in a method which specifically wraps around a long set of procedural steps. 我一直在尝试创建一个泛型工作者/线程类,它接受一个专门包含一长串程序步骤的方法。 The idea is to be able to pause/resume it a manner similar to setting breakpoints to pause/unpause in Visual Studio.
我们的想法是能够以类似于在Visual Studio中设置断点以暂停/取消暂停的方式暂停/恢复它。 To provide context, I'm mostly working with automation with an ASP.NET and XAML WPF interface (XAML at the moment).
为了提供上下文,我主要使用ASP.NET和XAML WPF接口(目前是XAML)进行自动化。
My understanding is that I need to use delegates of some sort but I'm looking for a very simple example in plain English. 我的理解是我需要使用某种代表,但我正在寻找一个简单的英语简单示例。 The examples I found are a completely different scope and I have a hard time following the provided solutions in other contexts.
我发现的示例是完全不同的范围,我很难跟踪其他环境中提供的解决方案。
From other examples on MSDN and Stackoverflow, the "Task" worker class is what I have so far, but I'm a bit at a loss on where to on DoDelegatedMethod and my constructor. 从MSDN和Stackoverflow上的其他示例来看,“Task”工作类是我到目前为止所做的,但是我对DoDelegatedMethod和我的构造函数的位置有点不知所措。 What I'm trying to do here is to instantiate a Task object, pass in a delegated method on new instantiation, create a new thread, and marry the passed in method to the thread.
我在这里要做的是实例化一个Task对象,在新实例化上传递一个委托方法,创建一个新线程,并将传入的方法结合到该线程。
The reason why I want a general "Task" is so I can manage specific methods generically instead of having to write a different "DoWork" method for each instance. 我之所以想要一般的“任务”,是因为我可以一般地管理特定的方法,而不必为每个实例编写不同的“DoWork”方法。
Is this the right approach? 这是正确的方法吗?
class Task
{
private ManualResetEvent _shutdownFlag = new ManualResetEvent(false);
private ManualResetEvent _pauseFlag = new ManualResetEvent(true);
private delegate void MyDelegate();
Thread _thread;
public Task() { }
public Task(MyDelegate d = new MyDelegate(DoStuff)) // ERROR
{
_thread = new Thread(DoDelegatedMethod); // ERROR
}
public void Start()
{
_thread.Start();
}
public void Resume()
{
_pauseFlag.Set(); ;
}
public void Stop()
{
_shutdownFlag.Set();
_pauseFlag.Set();
_thread.Join();
}
private void DoDelegatedMethod(MyDelegate d)
{
do
{
d();
}
while (!_shutdownFlag.WaitOne(0));
}
// This does nothing but spin forever until I force it to stop
public void Spin()
{
do
{
// MessageBox.Show("test");
_pauseFlag.WaitOne(Timeout.Infinite);
}
while (!_shutdownFlag.WaitOne(0));
//MessageBox.Show("thread over");
}
}
new Thread()
takes a ThreadStart (or ParameterisedThreadStart) argument, and your DoDelegatedMethod callback doesn't have the right signature for ThreadStart. new Thread()
接受一个ThreadStart(或ParameterisedThreadStart)参数,而你的DoDelegatedMethod回调没有ThreadStart的正确签名。 So you need to write something like this: 所以你需要写这样的东西:
ThreadStart method = new ThreadStart(() => DoDelegatedMethod(d));
_thread = new Thread(method);
This creates an anonymous callback (the () => DoDelegatedMethod(d)
bit) which when run will call DoDelegatedMethod with the delegate d
(which is 'captured' by the anonmyous method). 这将创建一个匿名回调(
() => DoDelegatedMethod(d)
位),在运行时将使用委托d
调用DoDelegatedMethod(由anonmyous方法“捕获”)。 Now you pass this anonymous callback to the Thread constructor, so when the thread runs, it will call the anonymous callback, which will in turn call DoDelegatedMethod(d). 现在你将这个匿名回调传递给Thread构造函数,所以当线程运行时,它将调用匿名回调,然后调用DoDelegatedMethod(d)。 Effectively the lambda adapts DoDelegatedMethod to the ThreadStart signature.
实际上,lambda使DoDelegatedMethod适应ThreadStart签名。
Another way to do this would be to change DoDelegatedMethod to take no arguments, and store d
as a member field of the Task class which DoDelegateMethod would access. 另一种方法是将DoDelegatedMethod更改为不带参数,并将
d
存储为DoDelegateMethod将访问的Task类的成员字段。
Also, the reason you get an error on your constructor is that default values can only be of a limited set of types, and delegates aren't one of them (only types that are allowed in attributes, like int, long, string and Type are permitted). 此外,构造函数出错的原因是默认值只能是有限的一组类型,并且委托不是其中之一(只有属性允许的类型,如int,long,string和Type是允许的)。 Use an overload instead:
改为使用过载:
public Task() : this(new MyDelegate(DoStuff)) { ... }
public Task(MyDelegate d) { ... }
Note you may still get an error if DoStuff is an instance method of Task -- it's not clear. 请注意,如果DoStuff是Task的实例方法,您仍可能会收到错误 - 它不清楚。 Personally I think having a default delegate for
Task
to run is a bit of an odd design, so you may just want to get rid of the default constructor. 我个人认为让
Task
运行的默认委托是一个奇怪的设计,所以你可能只想摆脱默认的构造函数。
Following the discussion in the comments I thought it was worth summarising the suggested revisions to the Task class: 在评论中讨论后,我认为值得总结一下Task类的建议修订:
public class Task
{
private readonly Action _action;
// other members as before
// default constructor removed
public Task(Action action)
{
_action = action;
}
public void Start()
{
ThreadStart ts = new ThreadStart(DoDelegatedMethod);
_thread = new Thread(ts);
_thread.Start();
}
private void DoDelegatedMethod()
{
do
{
_action();
}
while (!_shutdownFlag.WaitOne(0));
}
// other members as before
}
And the usage: 用法:
Task task = new Task(this.AutomatedTasks);
task.Start();
private void AutomatedTasks() { ... }
You may find good implementation of Task Pool manager here www.codeproject.com/KB/threads/smartthreadpool.aspx 您可以在这里找到任务池管理器的良好实现www.codeproject.com/KB/threads/smartthreadpool.aspx
smartthreadpool allows to send in pool any task, but you have to add Pause\\Start functions to it. smartthreadpool允许在池中发送任何任务,但您必须向其添加Pause \\ Start函数。
我会将这个列表模型化,我会像任何其他列表一样枚举,并在枚举器的en中使用'yield'。
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