EventInfo Class

Use the EventInfo class to inspect events and to hook up event handlers, as shown in the example code for the AddEventHandler method.

Note
EventInfo is not intended to be used to raise events. An object raises events as dictated by its internal state.

Events are used with delegates. An event listener instantiates an event-handler delegate that is invoked whenever the event is raised by an event source. In order to connect to the event source, the event listener adds this delegate to the invocation list on the source. When the event is raised, the invoke method of the event-handler delegate is called. Both multicast and single-cast event notifications are supported. The Add and Remove methods, as well as the event-handler delegate class associated with an event, must be marked in the metadata.

Delegates are object-oriented function pointers. In C or C++, a function pointer is a reference to a method. In contrast to the C or C++ function pointer, a delegate contains two references: a reference to a method and a reference to an object that supports the method. Delegates can invoke a method without knowing the class type that declares or inherits the method. Delegates need only know the return type and parameter list of the method.

The event model works equally well for single-cast and multicast delegates. When the delegate's invoke method is called, only a single object will have a method called on it. A multicast modifier can be applied to a delegate declaration, which allows multiple methods to be called when the invoke method of the delegate is called.

Calling ICustomAttributeProvider.GetCustomAttributes on EventInfo when the inherit parameter of GetCustomAttributes is true does not walk the type hierarchy. Use System.Attribute to inherit custom attributes.

When you inherit from EventInfo, you must override the following members: GetAddMethod, GetRemoveMethod, and GetRaiseMethod.

The following code gets an EventInfo object for the Click event of the Button class.

using System;
using System.Reflection;
using System.Security;

class MyEventExample
{
    public static void Main()
    {  
        try
        {

            // Creates a bitmask based on BindingFlags.
            BindingFlags myBindingFlags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;
            Type myTypeBindingFlags = typeof(System.Windows.Forms.Button);
            EventInfo myEventBindingFlags = myTypeBindingFlags.GetEvent("Click", myBindingFlags);
            if(myEventBindingFlags != null)
            {
                Console.WriteLine("Looking for the Click event in the Button class with the specified BindingFlags.");
                Console.WriteLine(myEventBindingFlags.ToString());
            }
            else
                Console.WriteLine("The Click event is not available with the Button class.");
        }
        catch(SecurityException e)
        {
            Console.WriteLine("An exception occurred.");
            Console.WriteLine("Message :"+e.Message);
        }
        catch(ArgumentNullException e)
        {
            Console.WriteLine("An exception occurred.");
            Console.WriteLine("Message :"+e.Message);
        }
        catch(Exception e)
        {
            Console.WriteLine("The following exception was raised : {0}",e.Message);
        }
    }
}

.NET Framework

.NET Framework Client Profile

Portable Class Library

• SecurityAction.InheritanceDemand  

  for full trust for inheritors. This class cannot be inherited by partially trusted code.

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

This type is thread safe.

Reference