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EventHandlerList Class

.NET Framework 4

Provides a simple list of delegates. This class cannot be inherited.

System.Object
  System.ComponentModel.EventHandlerList

Namespace:  System.ComponentModel
Assembly:  System (in System.dll)
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[HostProtectionAttribute(SecurityAction.LinkDemand, SharedState = true)]
public sealed class EventHandlerList : IDisposable

The EventHandlerList type exposes the following members.

  Name Description
Public method Supported by the XNA Framework EventHandlerList Initializes a new instance of the EventHandlerList class.
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  Name Description
Public property Supported by the XNA Framework Item Gets or sets the delegate for the specified object.
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  Name Description
Public method Supported by the XNA Framework AddHandler Adds a delegate to the list.
Public method Supported by the XNA Framework AddHandlers Adds a list of delegates to the current list.
Public method Supported by the XNA Framework Dispose Disposes the delegate list.
Public method Supported by the XNA Framework Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected method Supported by the XNA Framework Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method Supported by the XNA Framework GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public method Supported by the XNA Framework GetType Gets the Type of the current instance. (Inherited from Object.)
Protected method Supported by the XNA Framework MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public method Supported by the XNA Framework RemoveHandler Removes a delegate from the list.
Public method Supported by the XNA Framework ToString Returns a string that represents the current object. (Inherited from Object.)
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This class uses a linear search algorithm to find entries in the list of delegates. A linear search algorithm is inefficient when working with a large number of entries. Therefore, when you have a large list, finding entries is slow.

Note Note

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: SharedState. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

For an example of using an EventHandlerList, see How to: Handle Multiple Events Using Event Properties.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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Example for EventHandlerList
public class MyEventHandlerListClass
{
    private EventHandlerList _handlerList = new EventHandlerList();

    #region Events
    public event EventHandler Added
    { 
        add { _handlerList.AddHandler("Added", value); }
        remove { _handlerList.RemoveHandler("Added", value); }
    }

    public event EventHandler Removed
    {
        add { _handlerList.AddHandler("Removed", value); }
        remove { _handlerList.RemoveHandler("Removed", value); }
    }
    #endregion

    #region Private Methods
    private void FireAddedEvent()
    {
        EventHandler handler = (EventHandler)_handlerList["Added"];
        if (handler != null)
        {
        handler(this, new EventArgs());
        }
    }

    private void FireRemovedEvent()
    {
        EventHandler handler = (EventHandler)_handlerList["Removed"];
        if (handler != null)
        {
        handler(this, new EventArgs());
        }
    } 
    #endregion
}
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