InstanceDescriptor Class

Definition

Namespace:

System.ComponentModel.Design.Serialization

Assemblies:

netstandard.dll, System.ComponentModel.TypeConverter.dll

Source:

InstanceDescriptor.cs

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

C#

public sealed class InstanceDescriptor

Inheritance

Object

InstanceDescriptor

Examples

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

C#

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;
            }
        }
    }
}

Remarks

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.

Constructors

InstanceDescriptor(MemberInfo, ICollection, Boolean)	Initializes a new instance of the InstanceDescriptor class using the specified member information, arguments, and value indicating whether the specified information completely describes the instance.
InstanceDescriptor(MemberInfo, ICollection)	Initializes a new instance of the InstanceDescriptor class using the specified member information and arguments.

Properties

Arguments	Gets the collection of arguments that can be used to reconstruct an instance of the object that this instance descriptor represents.
IsComplete	Gets a value indicating whether the contents of this InstanceDescriptor completely identify the instance.
MemberInfo	Gets the member information that describes the instance this descriptor is associated with.

Methods

Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
Invoke()	Invokes this instance descriptor and returns the object the descriptor describes.
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)

Applies to

See also

• MemberInfo