PropertyDescriptor 类
定义
重要
一些信息与预发行产品相关,相应产品在发行之前可能会进行重大修改。 对于此处提供的信息,Microsoft 不作任何明示或暗示的担保。
提供类上属性的抽象。
public ref class PropertyDescriptor abstract : System::ComponentModel::MemberDescriptor
public abstract class PropertyDescriptor : System.ComponentModel.MemberDescriptor
[System.Runtime.InteropServices.ComVisible(true)]
public abstract class PropertyDescriptor : System.ComponentModel.MemberDescriptor
type PropertyDescriptor = class
inherit MemberDescriptor
[<System.Runtime.InteropServices.ComVisible(true)>]
type PropertyDescriptor = class
inherit MemberDescriptor
Public MustInherit Class PropertyDescriptor
Inherits MemberDescriptor
- 继承
- 派生
- 属性
示例
以下代码示例基于 PropertyDescriptorCollection 类中的示例生成。 它打印文本框中按钮文本的信息(类别、说明、显示名称)。 它假定在窗体上实例化了 button1
和 textbox1
。
// Creates a new collection and assign it the properties for button1.
PropertyDescriptorCollection^ properties = TypeDescriptor::GetProperties( button1 );
// Sets an PropertyDescriptor to the specific property.
System::ComponentModel::PropertyDescriptor^ myProperty = properties->Find( "Text", false );
// Prints the property and the property description.
textBox1->Text = String::Concat( myProperty->DisplayName, "\n" );
textBox1->Text = String::Concat( textBox1->Text, myProperty->Description, "\n" );
textBox1->Text = String::Concat( textBox1->Text, myProperty->Category, "\n" );
// Creates a new collection and assign it the properties for button1.
PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(button1);
// Sets an PropertyDescriptor to the specific property.
System.ComponentModel.PropertyDescriptor myProperty = properties.Find("Text", false);
// Prints the property and the property description.
textBox1.Text = myProperty.DisplayName + '\n';
textBox1.Text += myProperty.Description + '\n';
textBox1.Text += myProperty.Category + '\n';
' Creates a new collection and assign it the properties for button1.
Dim properties As PropertyDescriptorCollection = TypeDescriptor.GetProperties(Button1)
' Sets an PropertyDescriptor to the specific property.
Dim myProperty As PropertyDescriptor = properties.Find("Text", False)
' Prints the property and the property description.
TextBox1.Text += myProperty.DisplayName & Microsoft.VisualBasic.ControlChars.Cr
TextBox1.Text += myProperty.Description & Microsoft.VisualBasic.ControlChars.Cr
TextBox1.Text += myProperty.Category & Microsoft.VisualBasic.ControlChars.Cr
下面的代码示例演示如何实现一个自定义属性描述符,该描述符围绕属性提供只读包装器。 自定义设计器中使用 SerializeReadOnlyPropertyDescriptor
为控件的 Size 属性提供只读属性描述符。
using System;
using System.Collections;
using System.ComponentModel;
using System.Text;
namespace ReadOnlyPropertyDescriptorTest
{
// The SerializeReadOnlyPropertyDescriptor shows how to implement a
// custom property descriptor. It provides a read-only wrapper
// around the specified PropertyDescriptor.
internal sealed class SerializeReadOnlyPropertyDescriptor : PropertyDescriptor
{
private PropertyDescriptor _pd = null;
public SerializeReadOnlyPropertyDescriptor(PropertyDescriptor pd)
: base(pd)
{
this._pd = pd;
}
public override AttributeCollection Attributes
{
get
{
return( AppendAttributeCollection(
this._pd.Attributes,
ReadOnlyAttribute.Yes) );
}
}
protected override void FillAttributes(IList attributeList)
{
attributeList.Add(ReadOnlyAttribute.Yes);
}
public override Type ComponentType
{
get
{
return this._pd.ComponentType;
}
}
// The type converter for this property.
// A translator can overwrite with its own converter.
public override TypeConverter Converter
{
get
{
return this._pd.Converter;
}
}
// Returns the property editor
// A translator can overwrite with its own editor.
public override object GetEditor(Type editorBaseType)
{
return this._pd.GetEditor(editorBaseType);
}
// Specifies the property is read only.
public override bool IsReadOnly
{
get
{
return true;
}
}
public override Type PropertyType
{
get
{
return this._pd.PropertyType;
}
}
public override bool CanResetValue(object component)
{
return this._pd.CanResetValue(component);
}
public override object GetValue(object component)
{
return this._pd.GetValue(component);
}
public override void ResetValue(object component)
{
this._pd.ResetValue(component);
}
public override void SetValue(object component, object val)
{
this._pd.SetValue(component, val);
}
// Determines whether a value should be serialized.
public override bool ShouldSerializeValue(object component)
{
bool result = this._pd.ShouldSerializeValue(component);
if (!result)
{
DefaultValueAttribute dva = (DefaultValueAttribute)_pd.Attributes[typeof(DefaultValueAttribute)];
if (dva != null)
{
result = !Object.Equals(this._pd.GetValue(component), dva.Value);
}
else
{
result = true;
}
}
return result;
}
// The following Utility methods create a new AttributeCollection
// by appending the specified attributes to an existing collection.
static public AttributeCollection AppendAttributeCollection(
AttributeCollection existing,
params Attribute[] newAttrs)
{
return new AttributeCollection(AppendAttributes(existing, newAttrs));
}
static public Attribute[] AppendAttributes(
AttributeCollection existing,
params Attribute[] newAttrs)
{
if (existing == null)
{
throw new ArgumentNullException(nameof(existing));
}
newAttrs ??= new Attribute[0];
Attribute[] attributes;
Attribute[] newArray = new Attribute[existing.Count + newAttrs.Length];
int actualCount = existing.Count;
existing.CopyTo(newArray, 0);
for (int idx = 0; idx < newAttrs.Length; idx++)
{
if (newAttrs[idx] == null)
{
throw new ArgumentNullException("newAttrs");
}
// Check if this attribute is already in the existing
// array. If it is, replace it.
bool match = false;
for (int existingIdx = 0; existingIdx < existing.Count; existingIdx++)
{
if (newArray[existingIdx].TypeId.Equals(newAttrs[idx].TypeId))
{
match = true;
newArray[existingIdx] = newAttrs[idx];
break;
}
}
if (!match)
{
newArray[actualCount++] = newAttrs[idx];
}
}
// If some attributes were collapsed, create a new array.
if (actualCount < newArray.Length)
{
attributes = new Attribute[actualCount];
Array.Copy(newArray, 0, attributes, 0, actualCount);
}
else
{
attributes = newArray;
}
return attributes;
}
}
}
Imports System.Collections
Imports System.ComponentModel
Imports System.Text
' The SerializeReadOnlyPropertyDescriptor shows how to implement a
' custom property descriptor. It provides a read-only wrapper
' around the specified PropertyDescriptor.
Friend NotInheritable Class SerializeReadOnlyPropertyDescriptor
Inherits PropertyDescriptor
Private _pd As PropertyDescriptor = Nothing
Public Sub New(ByVal pd As PropertyDescriptor)
MyBase.New(pd)
Me._pd = pd
End Sub
Public Overrides ReadOnly Property Attributes() As AttributeCollection
Get
Return AppendAttributeCollection(Me._pd.Attributes, ReadOnlyAttribute.Yes)
End Get
End Property
Protected Overrides Sub FillAttributes(ByVal attributeList As IList)
attributeList.Add(ReadOnlyAttribute.Yes)
End Sub
Public Overrides ReadOnly Property ComponentType() As Type
Get
Return Me._pd.ComponentType
End Get
End Property
' The type converter for this property.
' A translator can overwrite with its own converter.
Public Overrides ReadOnly Property Converter() As TypeConverter
Get
Return Me._pd.Converter
End Get
End Property
' Returns the property editor
' A translator can overwrite with its own editor.
Public Overrides Function GetEditor(ByVal editorBaseType As Type) As Object
Return Me._pd.GetEditor(editorBaseType)
End Function
' Specifies the property is read only.
Public Overrides ReadOnly Property IsReadOnly() As Boolean
Get
Return True
End Get
End Property
Public Overrides ReadOnly Property PropertyType() As Type
Get
Return Me._pd.PropertyType
End Get
End Property
Public Overrides Function CanResetValue(ByVal component As Object) As Boolean
Return Me._pd.CanResetValue(component)
End Function
Public Overrides Function GetValue(ByVal component As Object) As Object
Return Me._pd.GetValue(component)
End Function
Public Overrides Sub ResetValue(ByVal component As Object)
Me._pd.ResetValue(component)
End Sub
Public Overrides Sub SetValue(ByVal component As Object, ByVal val As Object)
Me._pd.SetValue(component, val)
End Sub
' Determines whether a value should be serialized.
Public Overrides Function ShouldSerializeValue(ByVal component As Object) As Boolean
Dim result As Boolean = Me._pd.ShouldSerializeValue(component)
If Not result Then
Dim dva As DefaultValueAttribute = _
CType(_pd.Attributes(GetType(DefaultValueAttribute)), DefaultValueAttribute)
If Not (dva Is Nothing) Then
result = Not [Object].Equals(Me._pd.GetValue(component), dva.Value)
Else
result = True
End If
End If
Return result
End Function
' The following Utility methods create a new AttributeCollection
' by appending the specified attributes to an existing collection.
Public Shared Function AppendAttributeCollection( _
ByVal existing As AttributeCollection, _
ByVal ParamArray newAttrs() As Attribute) As AttributeCollection
Return New AttributeCollection(AppendAttributes(existing, newAttrs))
End Function
Public Shared Function AppendAttributes( _
ByVal existing As AttributeCollection, _
ByVal ParamArray newAttrs() As Attribute) As Attribute()
If existing Is Nothing Then
Throw New ArgumentNullException("existing")
End If
If newAttrs Is Nothing Then
newAttrs = New Attribute(-1) {}
End If
Dim attributes() As Attribute
Dim newArray(existing.Count + newAttrs.Length) As Attribute
Dim actualCount As Integer = existing.Count
existing.CopyTo(newArray, 0)
Dim idx As Integer
For idx = 0 To newAttrs.Length
If newAttrs(idx) Is Nothing Then
Throw New ArgumentNullException("newAttrs")
End If
' Check if this attribute is already in the existing
' array. If it is, replace it.
Dim match As Boolean = False
Dim existingIdx As Integer
For existingIdx = 0 To existing.Count - 1
If newArray(existingIdx).TypeId.Equals(newAttrs(idx).TypeId) Then
match = True
newArray(existingIdx) = newAttrs(idx)
Exit For
End If
Next existingIdx
If Not match Then
actualCount += 1
newArray(actualCount) = newAttrs(idx)
End If
Next idx
' If some attributes were collapsed, create a new array.
If actualCount < newArray.Length Then
attributes = New Attribute(actualCount) {}
Array.Copy(newArray, 0, attributes, 0, actualCount)
Else
attributes = newArray
End If
Return attributes
End Function
End Class
以下代码示例演示如何在自定义设计器中使用 SerializeReadOnlyPropertyDescriptor
。
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms.Design;
namespace ReadOnlyPropertyDescriptorTest
{
class DemoControlDesigner : ControlDesigner
{
// The PostFilterProperties method replaces the control's
// Size property with a read-only Size property by using
// the SerializeReadOnlyPropertyDescriptor class.
protected override void PostFilterProperties(IDictionary properties)
{
if (properties.Contains("Size"))
{
PropertyDescriptor original = properties["Size"] as PropertyDescriptor;
SerializeReadOnlyPropertyDescriptor readOnlyDescriptor =
new SerializeReadOnlyPropertyDescriptor(original);
properties["Size"] = readOnlyDescriptor;
}
base.PostFilterProperties(properties);
}
}
}
Imports System.Collections
Imports System.ComponentModel
Imports System.Text
Imports System.Windows.Forms.Design
Class DemoControlDesigner
Inherits ControlDesigner
' The PostFilterProperties method replaces the control's
' Size property with a read-only Size property by using
' the SerializeReadOnlyPropertyDescriptor class.
Protected Overrides Sub PostFilterProperties(ByVal properties As IDictionary)
If properties.Contains("Size") Then
Dim original As PropertyDescriptor = properties("Size")
Dim readOnlyDescriptor As New SerializeReadOnlyPropertyDescriptor(original)
properties("Size") = readOnlyDescriptor
End If
MyBase.PostFilterProperties(properties)
End Sub
End Class
using System.ComponentModel;
using System.Windows.Forms;
namespace ReadOnlyPropertyDescriptorTest
{
[Designer(typeof(DemoControlDesigner))]
public class DemoControl : Control
{
public DemoControl()
{
}
}
}
Imports System.ComponentModel
Imports System.ComponentModel.Design
Imports System.Text
Imports System.Windows.Forms
Imports System.Windows.Forms.Design
<Designer(GetType(DemoControlDesigner))> _
Public Class DemoControl
Inherits Control
Public Sub New()
End Sub
End Class
注解
属性的说明包括名称、其属性、属性关联的组件类以及属性的类型。
PropertyDescriptor 提供以下属性和方法:
Converter 包含此属性的 TypeConverter。
IsLocalizable 指示是否应本地化此属性。
GetEditor 返回指定类型的编辑器。
PropertyDescriptor 还提供以下 abstract
属性和方法:
ComponentType 包含此属性绑定到的组件类型。
IsReadOnly 指示此属性是否为只读。
PropertyType 获取属性的类型。
CanResetValue 指示重置组件是否更改组件的值。
GetValue 返回组件上属性的当前值。
ResetValue 重置组件的此属性的值。
SetValue 将组件的值设置为其他值。
ShouldSerializeValue 指示是否需要保留此属性的值。
通常,abstract
成员是通过反射实现的。 有关反射的详细信息,请参阅 反射中的主题。
构造函数
PropertyDescriptor(MemberDescriptor) |
使用指定 MemberDescriptor中的名称和属性初始化 PropertyDescriptor 类的新实例。 |
PropertyDescriptor(MemberDescriptor, Attribute[]) |
使用指定 MemberDescriptor 中的名称以及 MemberDescriptor 和 Attribute 数组中的属性初始化 PropertyDescriptor 类的新实例。 |
PropertyDescriptor(String, Attribute[]) |
使用指定的名称和属性初始化 PropertyDescriptor 类的新实例。 |
属性
AttributeArray |
获取或设置属性数组。 (继承自 MemberDescriptor) |
Attributes |
获取此成员的属性集合。 (继承自 MemberDescriptor) |
Category |
获取成员所属的类别的名称,如 CategoryAttribute中指定的。 (继承自 MemberDescriptor) |
ComponentType |
在派生类中重写时,获取此属性绑定到的组件的类型。 |
Converter |
获取此属性的类型转换器。 |
ConverterFromRegisteredType |
获取此属性的类型转换器。 |
Description |
获取成员的说明,如 DescriptionAttribute中指定的。 (继承自 MemberDescriptor) |
DesignTimeOnly |
获取是否仅在设计时设置此成员,如 DesignOnlyAttribute中指定的。 (继承自 MemberDescriptor) |
DisplayName |
获取可在窗口中显示的名称,例如“属性”窗口。 (继承自 MemberDescriptor) |
IsBrowsable |
获取一个值,该值指示成员是否可浏览,如 BrowsableAttribute中指定的值。 (继承自 MemberDescriptor) |
IsLocalizable |
获取一个值,该值指示是否应本地化此属性,如 LocalizableAttribute中指定的。 |
IsReadOnly |
在派生类中重写时,获取一个值,该值指示此属性是否为只读。 |
Name |
获取成员的名称。 (继承自 MemberDescriptor) |
NameHashCode |
获取成员名称的哈希代码,如 GetHashCode()中指定的。 (继承自 MemberDescriptor) |
PropertyType |
在派生类中重写时,获取属性的类型。 |
SerializationVisibility |
获取一个值,该值指示是否应按照 DesignerSerializationVisibilityAttribute中指定的方式序列化此属性。 |
SupportsChangeEvents |
获取一个值,该值指示此属性的值更改通知是否可能源自属性描述符外部。 |
方法
适用于
另请参阅
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