如何使用传递给system.threading.timer的状态对象？ [英] How do I use the state object passed to a system.threading.timer?

问题描述

我对 System.Threading.Timer 类感到有些困惑。以下代码编译并运行正常：

Hi,

I am a little confused by the System.Threading.Timer class. The following code compiles and runs fine:

using System;
using System.Threading;

namespace ConsoleApplication1
{
	public class Repeater
	{
		public Repeater( Action<object> callback, object state )
		{
			// Timer takes a TimerCallback delegate, but this constructor takes an Action<object>.  I have
			// read the easiest way to 'cast' a delegate is using lambdas.  Like this:
			TimerCallback tcb = ( s ) => callback( s );

			// So now I can construct my Timer.
			_timer = new Timer( tcb, state, 0, 5000 );
		}

		private Timer _timer = null;
	}

	public class Program
	{
		static void Main( string[] args )
		{
			Action<object> callback = MyFunction;
			Repeater repeater = new Repeater( callback, _count );

			Console.ReadKey();
		}

		private static void MyFunction( object state )
		{
			Console.WriteLine( $"event...{(int)state}" );
		}

		private static int _count = 42;
	}
}

每5秒打印一次事件...... 42。 />


当我在计时器上阅读MSDN文档时（Timer构造函数（TimerCallback，Object，Int64，Int64）（System.Threading）），它表示状态参数是：包含要由回调方法使用的信息的对象。这意味着每次调用时我都可以以某种方式将信息传递给回调函数。所以，在我上面的例子中，我可以找到一种方法让回调打印出42 ... 43 ... 44 ......等等。



是有没有办法做到这一点，或者是状态参数只能用作为回调委托指定某种初始状态的方式（正如我在这里所做的那样，有效地说，从42开始计数）？



亲切的愿望~Patrick



我的尝试：



给出的代码示例。我只是无法弄清楚如何编写任何比我现在做的更多的东西。

Every 5 seconds, it prints out "event...42".

When I read the MSDN documentation on Timer (Timer Constructor (TimerCallback, Object, Int64, Int64) (System.Threading)), it says that the state parameter is: "An object containing information to be used by the callback method." This implies I can somehow pass information into the callback function each time it is called. So, in my example above, I could find a way to get the callback to print out 42...43...44... etc.

Is there any way to do this, or is the state parameter usable only as a way to specify some kind of initial state for the callback delegate (as I have done here, by effectively saying, "Start counting from 42")?

Kind wishes ~ Patrick

What I have tried:

The code example given. I just can't work out how to write anything that does "more" than what I am doing already.

推荐答案

event ... {（int）state}）;
}

private static int _count = 42 ;
}
}

"event...{(int)state}" ); } private static int _count = 42; } }

每5秒打印一次事件...... 42。 />


当我在计时器上阅读MSDN文档时（Timer构造函数（TimerCallback，Object，Int64，Int64）（System.Threading）），它表示状态参数是：包含要由回调方法使用的信息的对象。这意味着每次调用时我都可以以某种方式将信息传递给回调函数。所以，在我上面的例子中，我可以找到一种方法让回调打印出42 ... 43 ... 44 ......等等。



是有没有办法做到这一点，或者是状态参数只能用作为回调委托指定某种初始状态的方式（正如我在这里所做的那样，有效地说，从42开始计数）？



亲切的愿望~Patrick



我的尝试：



给出的代码示例。我只是无法弄清楚如何编写任何比我现在做的更多的东西。

Every 5 seconds, it prints out "event...42".

When I read the MSDN documentation on Timer (Timer Constructor (TimerCallback, Object, Int64, Int64) (System.Threading)), it says that the state parameter is: "An object containing information to be used by the callback method." This implies I can somehow pass information into the callback function each time it is called. So, in my example above, I could find a way to get the callback to print out 42...43...44... etc.

Is there any way to do this, or is the state parameter usable only as a way to specify some kind of initial state for the callback delegate (as I have done here, by effectively saying, "Start counting from 42")?

Kind wishes ~ Patrick

What I have tried:

The code example given. I just can't work out how to write anything that does "more" than what I am doing already.

我不确定它是唯一的还是最好的解决方案，但以下是代码实现了我的目标。基本上，我所做的就是将哑整数_count变量更改为一个类，这意味着它通过引用传递，它可以保持自己的内部状态，如下所示：

I am not sure if it is the only or best solution, but the following code achieves what I was looking to do. Basically, all I have done is changed the "dumb" integer _count variable to a class, which means it is passed by reference and it can maintain its own internal state, like this:

using System;
using System.Threading;

namespace ConsoleApplication1
{
	public class Repeater
	{
		public Repeater( Action<object> callback, object state )
		{
			// Time takes a TimerCallback delegate, but this constructor takes an Action<object>.  I have
			// read the easiest way to 'cast' a delegate is using lambdas.  Like this:
			TimerCallback tcb = ( s ) => callback( s );

			// So now I can construct my Timer.
			_timer = new Timer( tcb, state, 0, 5000 );
		}

		private Timer _timer = null;
	}

	public class Counter
	{
		public int Count { get; set; }
	}

	public class Program
	{
		static void Main( string[] args )
		{
			Counter counter = new Counter();
			Action<object> callback = MyFunction;
			Repeater repeater = new Repeater( callback, counter );

			Console.ReadKey();
		}

		private static void MyFunction( object state )
		{
			Counter counter = state as Counter;
			Console.WriteLine(

event ... {counter .Count}）;
counter.Count = counter.Count + 1 ;
}
}
}

"event...{counter.Count}" ); counter.Count = counter.Count + 1; } } }

这似乎有效。我仍然会感激任何评论。

This seems to work. I would still appreciate any comments though.

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