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InstanceDescriptor Class

Provides the information necessary to create an instance of an object. This class cannot be inherited.

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

<PermissionSetAttribute(SecurityAction.LinkDemand, Name := "FullTrust")> _
<HostProtectionAttribute(SecurityAction.LinkDemand, SharedState := True)> _
Public NotInheritable Class InstanceDescriptor
Dim instance As InstanceDescriptor


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.

InstanceDescriptor can store information that describes an instance of an object. This information can be used to create an instance of the object.

Some custom serializers use InstanceDescriptor to represent serializable objects. Several methods of a TypeDescriptor use InstanceDescriptor to represent or instantiate objects.

An InstanceDescriptor provides the following members:

  • A MemberInfo property that describes this object.

  • An Arguments property that consists of the constructor arguments that can be used to instantiate this object.

  • A Boolean IsComplete property that indicates whether the object is completely represented by the current information.

  • An Invoke method that can be used to create an instance of the represented object.

The following code example illustrates how to use a type converter that participates in code generation through the use of instance descriptors.

Imports System
Imports System.ComponentModel
Imports System.ComponentModel.Design.Serialization
Imports System.Drawing
Imports System.Globalization
Imports System.Reflection
Namespace Microsoft.Samples.InstanceDescriptorSample

   '  This sample shows how to support code generation for a custom type  
   '  of object using a type converter and InstanceDescriptor objects. 
   '  To use this code, copy it to a file and add the file to a project.   
   '  Then add a component to the project and declare a Triangle field and  
   '  a public property with accessors for the Triangle field on the component. 
   '  The Triangle property will be persisted using code generation.

   <TypeConverter(GetType(Triangle.TriangleConverter))> _
   Public Class Triangle
      ' Triangle members. 
      Private P1 As Point
      Private P2 As Point
      Private P3 As Point

      Public Property Point1() As Point
            Return P1
         End Get 
         Set(ByVal Value As Point)
            P1 = Value
         End Set 
      End Property 

      Public Property Point2() As Point
            Return P2
         End Get 
         Set(ByVal Value As Point)
            P2 = Value
         End Set 
      End Property 

      Public Property Point3() As Point
            Return P3
         End Get 
         Set(ByVal Value As Point)
            P3 = Value
         End Set 
      End Property 

      Public Sub New(ByVal point1 As Point, ByVal point2 As Point, ByVal point3 As Point)
         P1 = point1
         P2 = point2
         P3 = point3
      End Sub 'New 

      ' A TypeConverter for the Triangle object.  Note that you can make it internal, 
      '  private, or any scope you want and the designers will still be able to use 
      '  it through the TypeDescriptor object.  This type converter provides the 
      '  capability to convert to an InstanceDescriptor.  This object can be used by  
      '  the .NET Framework to generate source code that creates an instance of a  
      '  Triangle object. 

      Friend Class TriangleConverter
         Inherits TypeConverter

         ' This method overrides CanConvertTo from TypeConverter.  This is called when someone 
         '  wants to convert an instance of Triangle to another type.  Here, 
         '  only coversition to an InstanceDescriptor is supported. 
         Public Overloads Overrides Function CanConvertTo(ByVal context As ITypeDescriptorContext, ByVal destinationType As Type) As Boolean 
            If destinationType Is GetType(InstanceDescriptor) Then 
               Return True 
            End If 

            ' Always call the base to see if it can perform the conversion. 
            Return MyBase.CanConvertTo(context, destinationType)
         End Function 

         ' This code performs the actual conversion from a Triangle to an InstanceDescriptor. 
         Public Overloads Overrides Function ConvertTo(ByVal context As ITypeDescriptorContext, ByVal culture As CultureInfo, ByVal value As Object, ByVal destinationType As Type) As Object
            If destinationType Is GetType(InstanceDescriptor) Then 
               Dim ci As ConstructorInfo = GetType(Triangle).GetConstructor(New Type() {GetType(Point), GetType(Point), GetType(Point)})
               Dim t As Triangle = CType(value, Triangle)
               Return New InstanceDescriptor(ci, New Object() {t.Point1, t.Point2, t.Point3})
            End If 

            ' Always call base, even if you can't convert. 
            Return MyBase.ConvertTo(context, culture, value, destinationType)
         End Function  
      End Class  
   End Class  

   Public Class TestComponent
      Inherits System.ComponentModel.Component
      Private myTriangleProp As Triangle

      Public Sub New()
         myTriangleProp = New Triangle(New Point(5, 5), _
                                    New Point(10, 10), New Point(1, 8))
      End Sub 

      Public Property MyTriangle() As Triangle
            Return myTriangleProp
         End Get 
         Set(ByVal Value As Triangle)
            myTriangleProp = Value
         End Set 
      End Property 

   End Class 

End Namespace


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