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ComponentEditor Class

Provides the base class for a custom component editor.

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

[HostProtectionAttribute(SecurityAction::LinkDemand, SharedState = true)]
public ref class ComponentEditor abstract

The ComponentEditor type exposes the following members.

Protected methodComponentEditorInitializes a new instance of the ComponentEditor class.

Public methodEditComponent(Object)Edits the component and returns a value indicating whether the component was modified.
Public methodEditComponent(ITypeDescriptorContext, Object)Edits the component and returns a value indicating whether the component was modified based upon a given context.
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)

A component editor is used to edit a component as a whole and can be used to implement a user interface similar to that of the property pages. You associate a component editor with a component by using the EditorAttribute attribute.


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.

Notes to Inheritors

When you inherit from this class, you must override the EditComponent method.

The following code example demonstrates an example ComponentEditor implementation.

#using <System.Windows.Forms.dll>
#using <System.Drawing.dll>
#using <System.dll>

using namespace System;
using namespace System::ComponentModel;
using namespace System::ComponentModel::Design;
using namespace System::Collections;
using namespace System::Drawing;
using namespace System::IO;
using namespace System::Runtime::Serialization;
using namespace System::Runtime::Serialization::Formatters::Binary;
using namespace System::Windows::Forms;
using namespace System::Windows::Forms::Design;

// This example demonstrates how to implement a component editor that hosts  
// component pages and associate it with a component. This example also  
// demonstrates how to implement a component page that provides a panel-based  
// control system and Help keyword support. 

   ref class ExampleComponentEditorPage;

   // The ExampleComponentEditor displays two ExampleComponentEditorPage pages. 
   public ref class ExampleComponentEditor: public System::Windows::Forms::Design::WindowsFormsComponentEditor

      // This method override returns an type array containing the type of  
      // each component editor page to display. 
      virtual array<Type^>^ GetComponentEditorPages() override
         array<Type^>^temp0 = {ExampleComponentEditorPage::typeid,ExampleComponentEditorPage::typeid};
         return temp0;

      // This method override returns the index of the page to display when the  
      // component editor is first displayed. 
      virtual int GetInitialComponentEditorPageIndex() override
         return 1;

   // This example component editor page type provides an example  
   // ComponentEditorPage implementation. 
   private ref class ExampleComponentEditorPage: public System::Windows::Forms::Design::ComponentEditorPage
      Label^ l1;
      Button^ b1;
      PropertyGrid^ pg1;

      // Base64-encoded serialized image data for the required component editor page icon.
      String^ icon;

         String^ temp = "AAEAAAD/////AQAAAAAAAAAMAgAAAFRTeXN0ZW0uRHJhd2luZywgVmVyc2lvbj0xLjAuNTAwMC4wLCBDdWx0dXJlPW5ldXRyYWwsIFB1YmxpY0tleVRva2VuPWIwM2Y1ZjdmMTFkNTBhM2EFAQAAABNTeXN0ZW0uRHJhd2luZy5JY29uAgAAAAhJY29uRGF0Y" 
         icon = temp;

         // Initialize the page, which inherits from Panel, and its controls. 
         this->Size = System::Drawing::Size( 400, 250 );
         this->Icon = DeserializeIconFromBase64Text( icon );
         this->Text = "Example Page";
         b1 = gcnew Button;
         b1->Size = System::Drawing::Size( 200, 20 );
         b1->Location = Point(200,0);
         b1->Text = "Set a random background color";
         b1->Click += gcnew EventHandler( this, &ExampleComponentEditorPage::randomBackColor );
         this->Controls->Add( b1 );
         l1 = gcnew Label;
         l1->Size = System::Drawing::Size( 190, 20 );
         l1->Location = Point(4,2);
         l1->Text = "Example Component Editor Page";
         this->Controls->Add( l1 );
         pg1 = gcnew PropertyGrid;
         pg1->Size = System::Drawing::Size( 400, 280 );
         pg1->Location = Point(0,30);
         this->Controls->Add( pg1 );

      // This method indicates that the Help button should be enabled for this  
      // component editor page. 
      virtual bool SupportsHelp() override
         return true;

      // This method is called when the Help button for this component editor page is pressed. 
      // This implementation uses the IHelpService to show the Help topic for a sample keyword. 
      virtual void ShowHelp() override
         // The GetSelectedComponent method of a ComponentEditorPage retrieves the 
         // IComponent associated with the WindowsFormsComponentEditor.
         IComponent^ selectedComponent = this->GetSelectedComponent();

         // Retrieve the Site of the component, and return if null.
         ISite^ componentSite = selectedComponent->Site;
         if ( componentSite == nullptr )

         // Acquire the IHelpService to display a help topic using a indexed keyword lookup.
         IHelpService^ helpService = dynamic_cast<IHelpService^>(componentSite->GetService( IHelpService::typeid ));
         if ( helpService != nullptr )
                  helpService->ShowHelpFromKeyword( "System.Windows.Forms.ComboBox" );


      // The LoadComponent method is raised when the ComponentEditorPage is displayed. 
      virtual void LoadComponent() override
         this->pg1->SelectedObject = this->Component;

      // The SaveComponent method is raised when the WindowsFormsComponentEditor is closing  
      // or the current ComponentEditorPage is closing. 
      virtual void SaveComponent() override {}


      // If the associated component is a Control, this method sets the BackColor to a random color. 
      // This method is invoked by the button on this ComponentEditorPage. 
      void randomBackColor( Object^ /*sender*/, EventArgs^ /*e*/ )
         if ( System::Windows::Forms::Control::typeid->IsAssignableFrom( this->::Component::GetType() ) )
            // Sets the background color of the Control associated with the 
            // WindowsFormsComponentEditor to a random color.
            Random^ rnd = gcnew Random;
            (dynamic_cast<System::Windows::Forms::Control^>(this->Component))->BackColor = Color::FromArgb( rnd->Next( 255 ), rnd->Next( 255 ), rnd->Next( 255 ) );

      // This method can be used to retrieve an Icon from a block  
      // of Base64-encoded text.
      System::Drawing::Icon^ DeserializeIconFromBase64Text( String^ text )
         System::Drawing::Icon^ img = nullptr;
         array<Byte>^memBytes = Convert::FromBase64String( text );
         IFormatter^ formatter = gcnew BinaryFormatter;
         MemoryStream^ stream = gcnew MemoryStream( memBytes );
         img = dynamic_cast<System::Drawing::Icon^>(formatter->Deserialize( stream ));
         return img;

   // This example control is associated with the ExampleComponentEditor  
   // through the following EditorAttribute.

   public ref class ExampleUserControl: public System::Windows::Forms::UserControl{};

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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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