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ComponentChangingEventArgs Class

Provides data for the ComponentChanging 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 ComponentChangingEventArgs : 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.

ComponentChangingEventArgs provides data about a ComponentChanging event. The ComponentChanging event notifies the IComponentChangeService and registered event handlers that a particular component in the current design document is about to be changed. This event provides a widely accessible method to prevent a component from changing.

A ComponentChanging event is raised before a component is changed. This event provides an opportunity for a designer to abort the change. Component designers typically raise the ComponentChanging event automatically. If a property cannot be changed, the method that handles the event can throw an exception. For example, if a designer file is checked into source code control, the handler of this event typically throws an exception if the user refuses to check out the file.

A ComponentChangingEventArgs provides the following information:

  • A Component property that indicates the component that is about to be modified.

  • A Member property that indicates the member that is about to be changed.

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 ComponentChangingEventArgs.

// This example method creates a ComponentChangingEventArgs using the specified arguments. 
// Typically, this type of event args is created by a design mode subsystem.   
public ComponentChangingEventArgs CreateComponentChangingEventArgs(object component, MemberDescriptor member)
    ComponentChangingEventArgs args = new ComponentChangingEventArgs(component, member);

    // The component that is about to change:       args.Component 
    // The member that is about to change:          args.Member 

    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