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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 sealed class InstanceDescriptor
NoteNote:

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.

namespace Microsoft.Samples.InstanceDescriptorSample
{
    using System;
    using System.ComponentModel;
    using System.ComponentModel.Design.Serialization;
    using System.Drawing;
    using System.Globalization;
    using System.Reflection;

    //  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(typeof(Triangle.TriangleConverter))]
    public class Triangle
    {
        // Triangle members.
        Point P1;
        Point P2;
        Point P3;

        public Point Point1 {
            get {
                return P1;
            }
            set {
                P1 = value;
            }
        }
        public Point Point2 {
            get 
            {
                return P2;
            }
            set 
            {
                P2 = value;
            }
        }
        public Point Point3 {
            get 
            {
                return P3;
            }
            set 
            {
                P3 = value;
            }
        }

        public Triangle(Point point1,Point point2,Point point3) {
            P1 = point1;
            P2 = point2;
            P3 = point3;
        }

        // 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. 
        internal class TriangleConverter : TypeConverter
        {
            // This method overrides CanConvertTo from TypeConverter. This is called when someone 
            //  wants to convert an instance of Triangle to another type.  Here, 
            //  only conversion to an InstanceDescriptor is supported. 
            public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
            {
                if (destinationType == typeof(InstanceDescriptor))
                {
                    return true;
                }

                // Always call the base to see if it can perform the conversion. 
                return base.CanConvertTo(context, destinationType);
            }

            // This code performs the actual conversion from a Triangle to an InstanceDescriptor. 
            public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
            {
                if (destinationType == typeof(InstanceDescriptor))
                {
                    ConstructorInfo ci = typeof(Triangle).GetConstructor(new Type[]{typeof(Point),
                                                    typeof(Point),typeof(Point)});
                    Triangle t = (Triangle) value;
                    return new InstanceDescriptor(ci,new object[]{t.Point1,t.Point2,t.Point3});
                }

                // Always call base, even if you can't convert. 
                return base.ConvertTo(context, culture, value, destinationType);
            }
        }
    }

    public class TestComponent : System.ComponentModel.Component 
    {
        Triangle myTriangle;

        public TestComponent() {
            myTriangle = new Triangle(
                new Point(5,5),
                new Point(10,10),
                new Point(1,8)
                );
        }

        public Triangle MyTriangle {
            get {
                return myTriangle;
            }
            set {
                myTriangle = value;
            }
        }
    }
}
System.Object
  System.ComponentModel.Design.Serialization.InstanceDescriptor
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
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