ITypeDescriptorContext 接口
提供有关组件的上下文信息，如其容器和属性描述符。
**命名空间:**System.ComponentModel
**程序集:**System（在 system.dll 中）
语法
声明
<ComVisibleAttribute(True)> _
Public Interface ITypeDescriptorContext
Inherits IServiceProvider
用法
Dim instance As ITypeDescriptorContext
[ComVisibleAttribute(true)]
public interface ITypeDescriptorContext : IServiceProvider
[ComVisibleAttribute(true)]
public interface class ITypeDescriptorContext : IServiceProvider
/** @attribute ComVisibleAttribute(true) */
public interface ITypeDescriptorContext extends IServiceProvider
ComVisibleAttribute(true)
public interface ITypeDescriptorContext extends IServiceProvider
备注
ITypeDescriptorContext 接口提供有关组件的上下文信息。ITypeDescriptorContext 通常在设计时用于提供有关设计时容器的信息。此接口通常用于类型转换中。有关详细信息，请参见 TypeConverter。
提示
当设计类型转换器时不要依赖于此接口的存在。如果特定的接口、属性或服务是必需的但不可用，则类型转换器应返回 空引用（在 Visual Basic 中为 Nothing） 而不是引发异常。此接口的属性可以随时返回 空引用（在 Visual Basic 中为 Nothing），您应为此做出计划。
示例
下面的代码示例演示如何使用 ITypeDescriptorContext 接口支持类型转换。
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
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;
}
}
}
}
#using <system.dll>
#using <system.drawing.dll>
using namespace System;
using namespace System::ComponentModel;
using namespace System::ComponentModel::Design::Serialization;
using namespace System::Drawing;
using namespace System::Globalization;
using namespace System::Collections;
using namespace 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.
*/
ref class TriangleConverter;
[TypeConverter(TriangleConverter::typeid)]
public ref class Triangle
{
private:
// Triangle members
Point P1;
Point P2;
Point P3;
public:
property Point Point1
{
Point get()
{
return P1;
}
void set( Point value )
{
P1 = value;
}
}
property Point Point2
{
Point get()
{
return P2;
}
void set( Point value )
{
P2 = value;
}
}
property Point Point3
{
Point get()
{
return P3;
}
void set( Point value )
{
P3 = value;
}
}
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. */
[System::Security::Permissions::PermissionSet(System::Security::
Permissions::SecurityAction::Demand, Name = "FullTrust")]
ref class TriangleConverter: public TypeConverter
{
public:
/* 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. */
virtual bool CanConvertTo( ITypeDescriptorContext^ context, Type^ destinationType ) override
{
if ( destinationType == InstanceDescriptor::typeid )
{
return true;
}
// Always call the base to see if it can perform the conversion.
return TypeConverter::CanConvertTo( context, destinationType );
}
/* This code performs the actual conversion from a Triangle to an InstanceDescriptor. */
virtual Object^ ConvertTo( ITypeDescriptorContext^ context, CultureInfo^ culture, Object^ value, Type^ destinationType ) override
{
if ( destinationType == InstanceDescriptor::typeid )
{
array<Type^>^type1 = {Point::typeid,Point::typeid,Point::typeid};
ConstructorInfo^ ci = Triangle::typeid->GetConstructor( type1 );
Triangle^ t = safe_cast<Triangle^>(value);
array<Object^>^obj1 = {t->Point1,t->Point2,t->Point3};
return gcnew InstanceDescriptor( ci,safe_cast<ICollection^>(obj1) );
}
// Always call base, even if you can't convert.
return TypeConverter::ConvertTo( context, culture, value, destinationType );
}
};
};
public ref class TestComponent: public System::ComponentModel::Component
{
private:
Triangle^ myTriangle;
public:
TestComponent()
{
myTriangle = gcnew Triangle( Point(5,5),Point(10,10),Point(1,8) );
}
property Triangle^ MyTriangle
{
Triangle^ get()
{
return myTriangle;
}
void set( Triangle^ value )
{
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
平台
Windows 98、Windows 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
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
请参见
参考
ITypeDescriptorContext 成员
System.ComponentModel 命名空间
TypeDescriptor
TypeConverter