EventArgs 类
EventArgs 是包含事件数据的类的基类。
**命名空间:**System
**程序集:**mscorlib（在 mscorlib.dll 中）
语法
声明
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public Class EventArgs
用法
Dim instance As EventArgs
[SerializableAttribute]
[ComVisibleAttribute(true)]
public class EventArgs
[SerializableAttribute]
[ComVisibleAttribute(true)]
public ref class EventArgs
/** @attribute SerializableAttribute() */
/** @attribute ComVisibleAttribute(true) */
public class EventArgs
SerializableAttribute
ComVisibleAttribute(true)
public class EventArgs
备注
此类不包含事件数据，在事件引发时不向事件处理程序传递状态信息的事件会使用此类。如果事件处理程序需要状态信息，则应用程序必须从此类派生一个类来保存数据。
例如，System.AssemblyLoadEventArgs 类用于保存程序集加载事件的数据，并包含描述所加载程序集的 System.Reflection.Assembly。
有关事件的更多信息，请参见 EventHandler 主题。
示例
下面的代码阐释了如何使用 EventArgs。
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。
Imports System
_
' FireEventArgs: a custom event inherited from EventArgs.
Public Class FireEventArgs
Inherits EventArgs
Public Sub New(room As String, ferocity As Integer)
Me.room = room
Me.ferocity = ferocity
End Sub 'New
' The fire event will have two pieces of information--
' 1) Where the fire is, and 2) how "ferocious" it is.
Public room As String
Public ferocity As Integer
End Class 'FireEventArgs
_
'end of class FireEventArgs
Public Class FireAlarm
' Events are handled with delegates, so we must establish a FireEventHandler
' as a delegate:
Delegate Sub FireEventHandler(sender As Object, fe As FireEventArgs)
' Now, create a public event "FireEvent" whose type is our FireEventHandler delegate.
Public Event FireEvent As FireEventHandler
' This will be the starting point of our event-- it will create FireEventArgs,
' and then raise the event, passing FireEventArgs.
Public Sub ActivateFireAlarm(room As String, ferocity As Integer)
Dim fireArgs As New FireEventArgs(room, ferocity)
' Now, raise the event by invoking the delegate. Pass in
' the object that initated the event (Me) as well as FireEventArgs.
' The call must match the signature of FireEventHandler.
RaiseEvent FireEvent(Me, fireArgs)
End Sub 'ActivateFireAlarm
End Class 'FireAlarm
' The following event will be the EventHandler.
Class FireHandlerClass
' Create a FireAlarm to handle and raise the fire events.
Public Sub New(fireAlarm As FireAlarm)
' Add a delegate containing the ExtinguishFire function to the class'
' event so that when FireAlarm is raised, it will subsequently execute
' ExtinguishFire.
AddHandler fireAlarm.FireEvent, AddressOf ExtinguishFire
End Sub 'New
' This is the function to be executed when a fire event is raised.
Sub ExtinguishFire(sender As Object, fe As FireEventArgs)
Console.WriteLine()
Console.WriteLine("The ExtinguishFire function was called by {0}.", sender.ToString())
' Now, act in response to the event.
If fe.ferocity < 2 Then
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 Then
Console.WriteLine("Using Fire Extinguisher 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 If
End If 'end of class FireHandlerClass
End Sub 'ExtinguishFire
End Class 'FireHandlerClass
Public Class FireEventTest
Public Shared Sub Main()
' Create an instance of the class that will be raising the event.
Dim myFireAlarm As 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.
Dim myFireHandler As New FireHandlerClass(myFireAlarm)
' Now, use the FireAlarm class to raise a few events.
myFireAlarm.ActivateFireAlarm("Kitchen", 3)
myFireAlarm.ActivateFireAlarm("Study", 1)
myFireAlarm.ActivateFireAlarm("Porch", 5)
Return
End Sub 'Main 'end of main
End Class 'FireEventTest ' end of FireEventTest
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
using namespace System;
// FireEventArgs: a custom event inherited from EventArgs.
public ref class FireEventArgs: public 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.
String^ room;
int ferocity;
};
//end of class FireEventArgs
// Class with a function that creates the eventargs and initiates the event
public ref class FireAlarm
{
public:
delegate void FireEventHandler( // Events are handled with delegates, so we must establish a FireEventHandler
// as a delegate:
Object^ sender, FireEventArgs^ fe );
event FireEventHandler^ FireEvent;
// Now, create a public event "FireEvent" whose type is our FireEventHandler delegate.
// This will be the starting point of our event-- it will create FireEventArgs,
// and then raise the event, passing FireEventArgs.
void ActivateFireAlarm( String^ room, int ferocity )
{
FireEventArgs^ fireArgs = gcnew 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
ref class FireHandlerClass
{
public:
// Create a FireAlarm to handle and raise the fire events.
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 += gcnew FireAlarm::FireEventHandler( this, &FireHandlerClass::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 );
// 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
int main()
{
// Create an instance of the class that will be firing an event.
FireAlarm^ myFireAlarm = gcnew 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 = gcnew 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 );
} //end of main
继承层次结构
System.Object
System.EventArgs
派生类
线程安全
此类型的任何公共静态（Visual Basic 中的 Shared）成员都是线程安全的，但不保证所有实例成员都是线程安全的。
平台
Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
.NET Compact Framework
受以下版本支持：2.0、1.0