ComponentEditor Class

Provides the base class for a custom component editor.

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

public abstract class ComponentEditor
public abstract class ComponentEditor
public abstract class ComponentEditor
Not applicable.

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 class 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;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Collections;
using System.Drawing;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.Windows.Forms;
using 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.
namespace ComponentEditorExample
    // The ExampleComponentEditor displays two ExampleComponentEditorPage pages.
    public class ExampleComponentEditor : System.Windows.Forms.Design.WindowsFormsComponentEditor
        // This method override returns an type array containing the type of 
        // each component editor page to display.
        protected override Type[] GetComponentEditorPages()
            return new Type[] { typeof(ExampleComponentEditorPage), 
                                typeof(ExampleComponentEditorPage) }; 
        // This method override returns the index of the page to display when the 
        // component editor is first displayed.
        protected override int GetInitialComponentEditorPageIndex()
            return 1; 
    // This example component editor page type provides an example 
    // ComponentEditorPage implementation.
    internal class ExampleComponentEditorPage : System.Windows.Forms.Design.ComponentEditorPage
        Label l1; 
        Button b1; 
        PropertyGrid pg1;

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

        public ExampleComponentEditorPage()
            // Initialize the page, which inherits from Panel, and its controls.
            this.Size = new Size( 400, 250 );            
            this.Icon = DeserializeIconFromBase64Text(icon);
            this.Text = "Example Page";
            b1 = new Button();
            b1.Size = new Size(200, 20);
            b1.Location = new Point(200, 0);
            b1.Text = "Set a random background color";
            b1.Click += new EventHandler(this.randomBackColor);
            this.Controls.Add( b1 );

            l1 = new Label();
            l1.Size = new Size(190, 20);
            l1.Location = new Point(4, 2);
            l1.Text = "Example Component Editor Page";
            this.Controls.Add( l1 );

            pg1 = new PropertyGrid();
            pg1.Size = new Size(400, 280);
            pg1.Location = new Point(0,30);
            this.Controls.Add( pg1 );
        // This method indicates that the Help button should be enabled for this 
        // component editor page.
        public override bool SupportsHelp()
            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.
        public override void ShowHelp()
            // 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 == null)
            // Acquire the IHelpService to display a help topic using a indexed keyword lookup.
            IHelpService helpService = (IHelpService)componentSite.GetService(typeof(IHelpService));
            if (helpService != null)

        // The LoadComponent method is raised when the ComponentEditorPage is displayed.
        protected override void LoadComponent()
            this.pg1.SelectedObject = this.Component; 
        // The SaveComponent method is raised when the WindowsFormsComponentEditor is closing 
        // or the current ComponentEditorPage is closing.
        protected override void SaveComponent()

        // 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.
        private void randomBackColor(object sender, EventArgs e)
            if( typeof(System.Windows.Forms.Control).IsAssignableFrom( this.Component.GetType() ) )
                // Sets the background color of the Control associated with the
                // WindowsFormsComponentEditor to a random color.
                Random rnd = new Random();
                ((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.
        private Icon DeserializeIconFromBase64Text(string text)
            Icon img = null;
            byte[] memBytes = Convert.FromBase64String(text);
            IFormatter formatter = new BinaryFormatter();
            MemoryStream stream = new MemoryStream(memBytes);
            img = (Icon)formatter.Deserialize(stream);
            return img;
    // This example control is associated with the ExampleComponentEditor 
    // through the following EditorAttribute.
    [EditorAttribute(typeof(ExampleComponentEditor), typeof(ComponentEditor))]
    public class ExampleUserControl : System.Windows.Forms.UserControl

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

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

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