System.EventArgs 类

System.EventArgs 类例子

在此示例中，FireEventArgs 是从 EventArgs 派生的事件参数集，它在调用 ActivateFireAlarm 引发事件时被传递到 FireEventHandler。

using System;

// FireEventArgs: a custom event inherited from EventArgs.

public class FireEventArgs: EventArgs {
	public FireEventArgs(string room, int ferocity) {
		this.room = room;
		this.ferocity = ferocity;
	}

	// The fire event will have two pieces of information-- 
	// 1) Where the fire is, and 2) how "ferocious" it is.  

	public string room;
	public int ferocity;

}	//end of class FireEventArgs


// Class with a function that creates the eventargs and initiates the event
public class FireAlarm {

	// Events are handled with delegates, so we must establish a FireEventHandler
	// as a delegate:

	public delegate void FireEventHandler(object sender, FireEventArgs fe);

	// Now, create a public event "FireEvent" whose type is our FireEventHandler delegate. 

	public event FireEventHandler FireEvent;	

	// This will be the starting point of our event-- it will create FireEventArgs,
	// and then raise the event, passing FireEventArgs. 

	public void ActivateFireAlarm(string room, int ferocity) {

		FireEventArgs fireArgs = new FireEventArgs(room, ferocity);

		// Now, raise the event by invoking the delegate. Pass in 
		// the object that initated the event (this) as well as FireEventArgs. 
		// The call must match the signature of FireEventHandler.

		FireEvent(this, fireArgs); 
	}
}	// end of class FireAlarm


// Class which handles the event

class FireHandlerClass {

	// Create a FireAlarm to handle and raise the fire events. 

	public FireHandlerClass(FireAlarm fireAlarm)	{

		// Add a delegate containing the ExtinguishFire function to the class'
		// event so that when FireAlarm is raised, it will subsequently execute 
		// ExtinguishFire.

		fireAlarm.FireEvent += new FireAlarm.FireEventHandler(ExtinguishFire);
	}

	// This is the function to be executed when a fire event is raised. 

	void ExtinguishFire(object sender, FireEventArgs fe) {

		Console.WriteLine("\nThe ExtinguishFire function was called by {0}.", sender.ToString());

		// Now, act in response to the event.

		if (fe.ferocity < 2)
			Console.WriteLine("This fire in the {0} is no problem.  I'm going to pour some water on it.", fe.room);
		else if (fe.ferocity < 5)
			Console.WriteLine("I'm using FireExtinguisher to put out the fire in the {0}.",  fe.room);
		else 
			Console.WriteLine("The fire in the {0} is out of control.  I'm calling the fire department!", fe.room);
	}
}	//end of class FireHandlerClass

public class FireEventTest {
	public static void Main () 	{	

		// Create an instance of the class that will be firing an event.

		FireAlarm myFireAlarm = new FireAlarm();
		
		// Create an instance of the class that will be handling the event. Note that 
		// it receives the class that will fire the event as a parameter. 

		FireHandlerClass myFireHandler = new FireHandlerClass(myFireAlarm);
		
		//use our class to raise a few events and watch them get handled
		myFireAlarm.ActivateFireAlarm("Kitchen", 3);
		myFireAlarm.ActivateFireAlarm("Study", 1);
		myFireAlarm.ActivateFireAlarm("Porch", 5);
		
		return;

	}	//end of main

}	// end of FireEventTest

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