EventArgs Class

Definition

public ref class EventArgs

public class EventArgs

[System.Serializable]
public class EventArgs

[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public class EventArgs

type EventArgs = class

[<System.Serializable>]
type EventArgs = class

[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type EventArgs = class

Public Class EventArgs

Inheritance

Object

EventArgs

Derived

Microsoft.VisualBasic.ApplicationServices.ApplyApplicationDefaultsEventArgs

Microsoft.VisualBasic.ApplicationServices.StartupNextInstanceEventArgs

Microsoft.VisualBasic.Devices.NetworkAvailableEventArgs

Microsoft.Win32.PowerModeChangedEventArgs

Microsoft.Win32.SessionEndedEventArgs

More…

Attributes

SerializableAttribute ComVisibleAttribute

Examples

The following example shows a custom event data class named ThresholdReachedEventArgs that derives from the EventArgs class. An instance of the event data class is passed to the event handler for the ThresholdReached event.

using System;

namespace ConsoleApplication3
{
 public class Program3
 {
 public static void Main()
 {
 Counter c = new(new Random().Next(10));
 c.ThresholdReached += c_ThresholdReached;

 Console.WriteLine("press 'a' key to increase total");
 while (Console.ReadKey(true).KeyChar == 'a')
 {
 Console.WriteLine("adding one");
 c.Add(1);
 }
 }

 static void c_ThresholdReached(object? sender, ThresholdReachedEventArgs e)
 {
 Console.WriteLine("The threshold of {0} was reached at {1}.", e.Threshold, e.TimeReached);
 Environment.Exit(0);
 }
 }

 class Counter
 {
 private readonly int _threshold;
 private int _total;

 public Counter(int passedThreshold)
 {
 _threshold = passedThreshold;
 }

 public void Add(int x)
 {
 _total += x;
 if (_total >= _threshold)
 {
 ThresholdReachedEventArgs args = new()
 {
 Threshold = _threshold,
 TimeReached = DateTime.Now
 };
 OnThresholdReached(args);
 }
 }

 protected virtual void OnThresholdReached(ThresholdReachedEventArgs e)
 {
 ThresholdReached?.Invoke(this, e);
 }

 public event EventHandler<ThresholdReachedEventArgs>? ThresholdReached;
 }

 public class ThresholdReachedEventArgs : EventArgs
 {
 public int Threshold { get; set; }
 public DateTime TimeReached { get; set; }
 }
}

open System

type ThresholdReachedEventArgs(threshold, timeReached) =
 inherit EventArgs()
 member _.Threshold = threshold
 member _.TimeReached = timeReached

type Counter(threshold) =
 let mutable total = 0

 let thresholdReached = Event<_>()

 member this.Add(x) =
 total <- total + x
 if total >= threshold then
 let args = ThresholdReachedEventArgs(threshold, DateTime.Now)
 thresholdReached.Trigger(this, args)

 [<CLIEvent>]
 member _.ThresholdReached = thresholdReached.Publish

let c_ThresholdReached(sender, e: ThresholdReachedEventArgs) =
 printfn $"The threshold of {e.Threshold} was reached at {e.TimeReached}."
 exit 0

let c = Counter(Random().Next 10)
c.ThresholdReached.Add c_ThresholdReached

printfn "press 'a' key to increase total"
while Console.ReadKey(true).KeyChar = 'a' do
 printfn "adding one"
 c.Add 1

Module Module1

 Sub Main()
 Dim c As Counter = New Counter(New Random().Next(10))
 AddHandler c.ThresholdReached, AddressOf c_ThresholdReached

 Console.WriteLine("press 'a' key to increase total")
 While Console.ReadKey(True).KeyChar = "a"
 Console.WriteLine("adding one")
 c.Add(1)
 End While
 End Sub

 Sub c_ThresholdReached(sender As Object, e As ThresholdReachedEventArgs)
 Console.WriteLine("The threshold of {0} was reached at {1}.", e.Threshold, e.TimeReached)
 Environment.Exit(0)
 End Sub
End Module

Class Counter
 Private threshold As Integer
 Private total As Integer

 Public Sub New(passedThreshold As Integer)
 threshold = passedThreshold
 End Sub

 Public Sub Add(x As Integer)
 total = total + x
 If (total >= threshold) Then
 Dim args As ThresholdReachedEventArgs = New ThresholdReachedEventArgs()
 args.Threshold = threshold
 args.TimeReached = DateTime.Now
 OnThresholdReached(args)
 End If
 End Sub

 Protected Overridable Sub OnThresholdReached(e As ThresholdReachedEventArgs)
 RaiseEvent ThresholdReached(Me, e)
 End Sub

 Public Event ThresholdReached As EventHandler(Of ThresholdReachedEventArgs)
End Class

Class ThresholdReachedEventArgs
 Inherits EventArgs

 Public Property Threshold As Integer
 Public Property TimeReached As DateTime
End Class

Remarks

This class serves as the base class for all classes that represent event data. For example, the System.AssemblyLoadEventArgs class derives from EventArgs and is used to hold the data for assembly load events. To create a custom event data class, create a class that derives from the EventArgs class and provide the properties to store the necessary data. The name of your custom event data class should end with EventArgs.

To pass an object that does not contain any data, use the Empty field.

For more information about events, see the Handling and Raising Events article.

See also

• Handling and Raising Events
• How to: Raise and Consume Events
• Events (Visual Basic)
• Events (C# Programming Guide)
• Events and routed events overview (Windows store apps)