PropertyDescriptor 類別

定義

提供類別上屬性的抽象。Provides an abstraction of a property on a class.

public ref class PropertyDescriptor abstract : System::ComponentModel::MemberDescriptor
[System.Runtime.InteropServices.ComVisible(true)]
public abstract class PropertyDescriptor : System.ComponentModel.MemberDescriptor
type PropertyDescriptor = class
    inherit MemberDescriptor
Public MustInherit Class PropertyDescriptor
Inherits MemberDescriptor
繼承
PropertyDescriptor
衍生
屬性

範例

下列程式碼範例是根據 PropertyDescriptorCollection 類別中的範例所建立。The following code example is built upon the example in the PropertyDescriptorCollection class. 它會在文字方塊中列印按鈕文字的資訊(類別、描述、顯示名稱)。It prints the information (category, description, display name) of the text of a button in a text box. 它假設 button1textbox1 已經在表單上具現化。It assumes that button1 and textbox1 have been instantiated on a form.

// 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

下列程式碼範例示範如何執行自訂屬性描述元,以提供屬性周圍的唯讀包裝函式。The following code example shows how to implement a custom property descriptor that provides a read-only wrapper around a property. 在自訂設計工具中使用 SerializeReadOnlyPropertyDescriptor,為控制項的 Size 屬性提供唯讀屬性描述項。The SerializeReadOnlyPropertyDescriptor is used in a custom designer to provide a read-only property descriptor for the control's Size property.

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

下列程式碼範例示範如何在自訂設計工具中使用 SerializeReadOnlyPropertyDescriptorThe following code examples show how to use the SerializeReadOnlyPropertyDescriptor in a custom designer.

using System;
using System.Collections;
using System.ComponentModel;
using System.Text;
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;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Text;
using System.Windows.Forms;
using System.Windows.Forms.Design;

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

備註

屬性的描述包含名稱、其屬性、與屬性相關聯的元件類別,以及屬性的類型。A description of a property consists of a name, its attributes, the component class that the property is associated with, and the type of the property.

PropertyDescriptor 提供下列屬性和方法:PropertyDescriptor provides the following properties and methods:

PropertyDescriptor 也提供下列 @no__t 1 的屬性和方法:PropertyDescriptor also provides the following abstract properties and methods:

  • ComponentType 包含此屬性所系結之元件的類型。ComponentType contains the type of component this property is bound to.

  • IsReadOnly 表示此屬性是否為唯讀。IsReadOnly indicates whether this property is read-only.

  • PropertyType 會取得屬性的類型。PropertyType gets the type of the property.

  • CanResetValue 表示重設元件是否變更元件的值。CanResetValue indicates whether resetting the component changes the value of the component.

  • GetValue 會傳回元件上屬性的目前值。GetValue returns the current value of the property on a component.

  • ResetValue 會重設元件之這個屬性的值。ResetValue resets the value for this property of the component.

  • SetValue 會將元件的值設定為不同的值。SetValue sets the value of the component to a different value.

  • ShouldSerializeValue 表示是否需要保存此屬性的值。ShouldSerializeValue indicates whether the value of this property needs to be persisted.

一般來說,@no__t 0 的成員會透過反映來執行。Typically, the abstract members are implemented through reflection. 如需反映的詳細資訊,請參閱反映中的主題。For more information about reflection, see the topics in Reflection.

建構函式

PropertyDescriptor(MemberDescriptor)

使用指定 PropertyDescriptor 中的名稱和屬性,初始化 MemberDescriptor 類別的新執行個體。Initializes a new instance of the PropertyDescriptor class with the name and attributes in the specified MemberDescriptor.

PropertyDescriptor(MemberDescriptor, Attribute[])

使用指定 PropertyDescriptor 中的名稱,以及 MemberDescriptorMemberDescriptor 陣列中的屬性,初始化 Attribute 類別的新執行個體。Initializes a new instance of the PropertyDescriptor class with the name in the specified MemberDescriptor and the attributes in both the MemberDescriptor and the Attribute array.

PropertyDescriptor(String, Attribute[])

使用指定的名稱和屬性,初始化 PropertyDescriptor 類別的新執行個體。Initializes a new instance of the PropertyDescriptor class with the specified name and attributes.

屬性

AttributeArray

取得或設定屬性的陣列。Gets or sets an array of attributes.

(繼承來源 MemberDescriptor)
Attributes

取得這個成員的屬性集合。Gets the collection of attributes for this member.

(繼承來源 MemberDescriptor)
Category

取得成員所屬的分類名稱,如 CategoryAttribute 中所指定的。Gets the name of the category to which the member belongs, as specified in the CategoryAttribute.

(繼承來源 MemberDescriptor)
ComponentType

在衍生類別中覆寫時,取得這個屬性所繫結的元件型別。When overridden in a derived class, gets the type of the component this property is bound to.

Converter

取得這個屬性的型別轉換子。Gets the type converter for this property.

Description

取得成員的描述,如 DescriptionAttribute 中所指定的。Gets the description of the member, as specified in the DescriptionAttribute.

(繼承來源 MemberDescriptor)
DesignTimeOnly

取得值,表示這個成員是否只在設計階段設定,如 DesignOnlyAttribute 中所指定的。Gets whether this member should be set only at design time, as specified in the DesignOnlyAttribute.

(繼承來源 MemberDescriptor)
DisplayName

取得可在視窗 (例如 [屬性] 視窗) 中顯示的名稱。Gets the name that can be displayed in a window, such as a Properties window.

(繼承來源 MemberDescriptor)
IsBrowsable

取得值,表示成員是否可瀏覽,如 BrowsableAttribute 中指定的。Gets a value indicating whether the member is browsable, as specified in the BrowsableAttribute.

(繼承來源 MemberDescriptor)
IsLocalizable

取得值,表示這個屬性是否應該當地語系化,如 LocalizableAttribute 中指定的。Gets a value indicating whether this property should be localized, as specified in the LocalizableAttribute.

IsReadOnly

在衍生類別中覆寫時,取得數值以指示這個屬性是否為唯讀。When overridden in a derived class, gets a value indicating whether this property is read-only.

Name

取得成員的名稱。Gets the name of the member.

(繼承來源 MemberDescriptor)
NameHashCode

取得成員名稱的雜湊程式碼,如 GetHashCode() 中所指定的。Gets the hash code for the name of the member, as specified in GetHashCode().

(繼承來源 MemberDescriptor)
PropertyType

在衍生類別中覆寫時,取得屬性的型別。When overridden in a derived class, gets the type of the property.

SerializationVisibility

取得值,表示這個屬性是否應該序列化,如 DesignerSerializationVisibilityAttribute 中指定的。Gets a value indicating whether this property should be serialized, as specified in the DesignerSerializationVisibilityAttribute.

SupportsChangeEvents

取得值,表示這個屬性的數值變更告知是否可能來自屬性描述項之外。Gets a value indicating whether value change notifications for this property may originate from outside the property descriptor.

方法

AddValueChanged(Object, EventHandler)

使其他物件能在這個屬性變更時受到告知。Enables other objects to be notified when this property changes.

CanResetValue(Object)

在衍生類別中覆寫時,傳回重設物件是否變更其值。When overridden in a derived class, returns whether resetting an object changes its value.

CreateAttributeCollection()

使用傳遞給建構函式的屬性陣列,建立屬性的集合。Creates a collection of attributes using the array of attributes passed to the constructor.

(繼承來源 MemberDescriptor)
CreateInstance(Type)

建立指定類型的執行個體。Creates an instance of the specified type.

Equals(Object)

比較這個與另一個物件,以檢視它們是否相等。Compares this to another object to see if they are equivalent.

FillAttributes(IList)

PropertyDescriptor 的屬性加入至父類別中的指定屬性清單。Adds the attributes of the PropertyDescriptor to the specified list of attributes in the parent class.

GetChildProperties()

傳回預設的 PropertyDescriptorCollectionReturns the default PropertyDescriptorCollection.

GetChildProperties(Attribute[])

使用指定的屬性陣列做為篩選條件,傳回 PropertyDescriptorCollectionReturns a PropertyDescriptorCollection using a specified array of attributes as a filter.

GetChildProperties(Object)

傳回指定物件的 PropertyDescriptorCollectionReturns a PropertyDescriptorCollection for a given object.

GetChildProperties(Object, Attribute[])

使用指定的屬性陣列做為篩選條件,傳回指定物件的 PropertyDescriptorCollectionReturns a PropertyDescriptorCollection for a given object using a specified array of attributes as a filter.

GetEditor(Type)

取得指定型別的編輯器。Gets an editor of the specified type.

GetHashCode()

傳回這個物件的雜湊程式碼。Returns the hash code for this object.

GetInvocationTarget(Type, Object)

這個方法會傳回應該在成員的引動過程使用的物件。This method returns the object that should be used during invocation of members.

GetType()

取得目前執行個體的 TypeGets the Type of the current instance.

(繼承來源 Object)
GetTypeFromName(String)

使用其名稱以傳回型別。Returns a type using its name.

GetValue(Object)

在衍生類別中覆寫時,取得元件上屬性的目前值。When overridden in a derived class, gets the current value of the property on a component.

GetValueChangedHandler(Object)

擷取特定元件目前的 ValueChanged 事件處理常式集。Retrieves the current set of ValueChanged event handlers for a specific component.

MemberwiseClone()

建立目前 Object 的淺層複本 (Shallow Copy)。Creates a shallow copy of the current Object.

(繼承來源 Object)
OnValueChanged(Object, EventArgs)

引發您之前實作的 ValueChanged 事件。Raises the ValueChanged event that you implemented.

RemoveValueChanged(Object, EventHandler)

使其他物件能在這個屬性變更時受到告知。Enables other objects to be notified when this property changes.

ResetValue(Object)

在衍生類別中覆寫時,將元件的這個屬性值重設為預設值。When overridden in a derived class, resets the value for this property of the component to the default value.

SetValue(Object, Object)

在衍生類別中覆寫時,將元件的值設定為不同的值。When overridden in a derived class, sets the value of the component to a different value.

ShouldSerializeValue(Object)

在衍生類別中覆寫時,判斷指示這個屬性的值是否需要保存的值。When overridden in a derived class, determines a value indicating whether the value of this property needs to be persisted.

ToString()

傳回代表目前物件的字串。Returns a string that represents the current object.

(繼承來源 Object)

適用於

另請參閱