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ComponentChangedEventArgs Class

Provides data for the ComponentChanged event. This class cannot be inherited.

Namespace:  System.ComponentModel.Design
Assembly:  System (in System.dll)

[PermissionSetAttribute(SecurityAction.LinkDemand, Name = "FullTrust")]
[HostProtectionAttribute(SecurityAction.LinkDemand, SharedState = true)]
public sealed class ComponentChangedEventArgs : EventArgs


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.

ComponentChangedEventArgs provides data for a ComponentChanged event. The ComponentChanged event notifies the IComponentChangeService and registered event handlers that a particular component in the currently active document has been changed.

A ComponentChangedEventArgs provides the following information:

  • A Component property that indicates the component that was modified.

  • A Member property that indicates the member that was changed.

  • A NewValue property that indicates the new value of the member.

  • An OldValue property that indicates the old value of the member.

Component designers typically raise the ComponentChanged event automatically when components are added, removed, or modified. A ComponentChanged event is not raised during form load and unload because changes at this time are expected. A component designer might raise the ComponentChanged event after it changes a property of the component; this ensures that the Properties window will display the updated property.

Notes to Inheritors:

A compiler error occurs if this class is specified as the base class of another class.

The following example demonstrates creating a ComponentChangedEventArgs.

// This example method creates a ComponentChangedEventArgs using the specified arguments. 
// Typically, this type of event args is created by a design mode subsystem.             
public ComponentChangedEventArgs CreateComponentChangedEventArgs(object component, MemberDescriptor member, object oldValue, object newValue)
    // Creates a component changed event args with the specified arguments.
    ComponentChangedEventArgs args = new ComponentChangedEventArgs(component, member, oldValue, newValue);

    // The component that has changed:              args.Component 
    // The member of the component that changed:    args.Member 
    // The old value of the member:                 args.oldValue 
    // The new value of the member:                 args.newValue 

    return args;            


Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

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