ITypeDescriptorContext Interface
Assembly: System (in system.dll)
'Declaration <ComVisibleAttribute(True)> _ Public Interface ITypeDescriptorContext Inherits IServiceProvider 'Usage Dim instance As ITypeDescriptorContext
/** @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.
Note: |
|---|
| 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.
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 Get Return P1 End Get Set(ByVal Value As Point) P1 = Value End Set End Property Public Property Point2() As Point Get Return P2 End Get Set(ByVal Value As Point) P2 = Value End Set End Property Public Property Point3() As Point Get 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 Get Return myTriangleProp End Get Set(ByVal Value As Triangle) myTriangleProp = Value End Set End Property End Class End Namespace
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.
Note: