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ITypeDescriptorContext Interface

Provides contextual information about a component, such as its container and property descriptor.

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

[ComVisibleAttribute(true)] 
public interface ITypeDescriptorContext : IServiceProvider
/** @attribute ComVisibleAttribute(true) */ 
public interface ITypeDescriptorContext extends IServiceProvider
ComVisibleAttribute(true) 
public interface ITypeDescriptorContext extends IServiceProvider
Not applicable.

The ITypeDescriptorContext interface provides contextual information about a component. ITypeDescriptorContext is typically used at design time to provide information about a design-time container. This interface is commonly used in type conversion. For details, see TypeConverter.

NoteNote:

Do not rely on the presence of this interface when you design a type converter. If a particular interface, property, or service is necessary but not available, the type converter should return a null reference (Nothing in Visual Basic) rather than throw an exception. This interface's properties can return a null reference (Nothing in Visual Basic) at any time, and you should plan for this.

The following code example demonstrates how to use the ITypeDescriptorContext interface to support type conversion.

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;
            }
        }
    }
}

package Microsoft.Samples.InstanceDescriptorSample; 

import System.*;
import System.ComponentModel.*;
import System.ComponentModel.Design.Serialization.*;
import System.Drawing.*;
import System.Globalization.*;
import 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.
/** @ attribute TypeConverter(Triangle.TriangleConverter .class.ToType())
 */
public class Triangle
{
    // Triangle members.
    private Point P1;
    private Point P2;
    private Point P3;

    /** @property 
     */
    public Point get_Point1()
    {
        return P1;
    } //get_Point1

    /** @property 
     */
    public void set_Point1(Point value)
    {
        P1 = value;
    } //set_Point1

    /** @property 
     */
    public Point get_Point2()
    {
        return P2;
    } //get_Point2

    /** @property 
     */
    public void set_Point2(Point value)
    {
        P2 = value;
    } //set_Point2

    /** @property 
     */
    public Point get_Point3()
    {
        return P3;
    } //get_Point3

    /** @property 
     */
    public void set_Point3(Point value)
    {
        P3 = value;
    } //set_Point3

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

    // 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.
    class TriangleConverter extends 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 boolean CanConvertTo(ITypeDescriptorContext context,
            Type destinationType)
        {
            if (destinationType.Equals(InstanceDescriptor.class.ToType())) {
                return true;
            }
            // Always call the base to see if it can perform the conversion.
            return super.CanConvertTo(context, destinationType);
        } //CanConvertTo

        // This code performs the actual conversion from a Triangle to an 
        //InstanceDescriptor.
        public Object ConvertTo(ITypeDescriptorContext context,
            CultureInfo culture, Object value, Type destinationType)
        {
            if (destinationType.Equals(InstanceDescriptor.class.ToType())) {
                ConstructorInfo ci = Triangle.class.ToType().GetConstructor(
                    new Type[] { Point.class.ToType(), Point.class.ToType(),
                    Point.class.ToType() });
                Triangle t = ((Triangle)(value));
                return new InstanceDescriptor(ci, new Object[] { t.get_Point1(),
                    t.get_Point2(), t.get_Point3() });
            }
            // Always call base, even if you can't convert.
            return super.ConvertTo(context, culture, value, destinationType);
        } //ConvertTo
    } //TriangleConverter
} //Triangle

public class TestComponent extends System.ComponentModel.Component
{
    private Triangle myTriangle;

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

    /** @property 
     */
    public Triangle get_MyTriangle()
    {
        return myTriangle;
    } //get_MyTriangle

    /** @property 
     */
    public void set_MyTriangle(Triangle value)
    {
        myTriangle = value;
    } //set_MyTriangle
} //TestComponent

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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