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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 MustInherit Class ComponentEditor

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.

Imports System
Imports System.ComponentModel
Imports System.ComponentModel.Design
Imports System.Collections
Imports System.Drawing
Imports System.IO
Imports System.Runtime.Serialization
Imports System.Runtime.Serialization.Formatters.Binary
Imports System.Windows.Forms
Imports 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. 
' The ExampleComponentEditor displays two ExampleComponentEditorPage pages. 
Public Class ExampleComponentEditor
    Inherits System.Windows.Forms.Design.WindowsFormsComponentEditor

    ' This method override returns an type array containing the type of  
    ' each component editor page to display. 
    Protected Overrides Function GetComponentEditorPages() As Type()
        Return New Type() {GetType(ExampleComponentEditorPage), GetType(ExampleComponentEditorPage)}
    End Function 

    ' This method override returns the index of the page to display when the  
    ' component editor is first displayed. 
    Protected Overrides Function GetInitialComponentEditorPageIndex() As Integer 
        Return 1
    End Function 

    Public Overloads Overrides Function EditComponent(ByVal context As System.ComponentModel.ITypeDescriptorContext, ByVal component As Object) As Boolean 

    End Function 
End Class 

' This example component editor page type provides an example  
' ComponentEditorPage implementation. 
Friend Class ExampleComponentEditorPage
    Inherits System.Windows.Forms.Design.ComponentEditorPage
    Private l1 As Label
    Private b1 As Button
    Private pg1 As PropertyGrid

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

    Public Sub New()
        ' Initialize the page, which inherits from Panel, and its controls. 
        Me.Size = New Size(400, 250)
        Me.Icon = DeserializeIconFromBase64Text(icondata)
        Me.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" 
        AddHandler b1.Click, AddressOf Me.randomBackColor

        l1 = New Label
        l1.Size = New Size(190, 20)
        l1.Location = New Point(4, 2)
        l1.Text = "Example Component Editor Page" 

        pg1 = New PropertyGrid
        pg1.Size = New Size(400, 280)
        pg1.Location = New Point(0, 30)
    End Sub 

    ' This method indicates that the Help button should be enabled for this  
    ' component editor page. 
    Public Overrides Function SupportsHelp() As Boolean 
        Return True 
    End Function 

    ' 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 Overrides Sub ShowHelp()
        ' The GetSelectedComponent method of a ComponentEditorPage retrieves the 
        ' IComponent associated with the WindowsFormsComponentEditor. 
        Dim selectedComponent As IComponent = Me.GetSelectedComponent()

        ' Retrieve the Site of the component, and return if null. 
        Dim componentSite As ISite = selectedComponent.Site
        If componentSite Is Nothing Then 
        End If 
        ' Acquire the IHelpService to display a help topic using a indexed keyword lookup. 
        Dim helpService As IHelpService = CType(componentSite.GetService(GetType(IHelpService)), IHelpService)
        If (helpService IsNot Nothing) Then
        End If 
    End Sub 

    ' The LoadComponent method is raised when the ComponentEditorPage is displayed. 
    Protected Overrides Sub LoadComponent()
        Me.pg1.SelectedObject = Me.Component
    End Sub 

    ' The SaveComponent method is raised when the WindowsFormsComponentEditor is closing  
    ' or the current ComponentEditorPage is closing. 
    Protected Overrides Sub SaveComponent()
    End Sub 

    ' 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 Sub randomBackColor(ByVal sender As Object, ByVal e As EventArgs)
        If GetType(System.Windows.Forms.Control).IsAssignableFrom(CType(Me.Component, Object).GetType()) Then 
            ' Sets the background color of the Control associated with the 
            ' WindowsFormsComponentEditor to a random color. 
            Dim rnd As New Random
            CType(Me.Component, System.Windows.Forms.Control).BackColor = Color.FromArgb(rnd.Next(255), rnd.Next(255), rnd.Next(255))
        End If 
    End Sub 

    ' This method can be used to retrieve an Icon from a block  
    ' of Base64-encoded text. 
    Private Function DeserializeIconFromBase64Text(ByVal [text] As String) As icon
        Dim img As Icon = Nothing 
        Dim memBytes As Byte() = Convert.FromBase64String([text])
        Dim formatter As New BinaryFormatter
        Dim stream As New MemoryStream(memBytes)
        img = CType(formatter.Deserialize(stream), Icon)
        Return img
    End Function 
End Class 

' This example control is associated with the ExampleComponentEditor  
' through the following EditorAttribute.
<EditorAttribute(GetType(ExampleComponentEditor), GetType(ComponentEditor))> _
Public Class ExampleUserControl
    Inherits System.Windows.Forms.UserControl
End Class

.NET Framework

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

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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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