PropertyDescriptor Class
Provides an abstraction of a property on a class.
Assembly: System (in System.dll)
System.ComponentModel.MemberDescriptor
System.ComponentModel.PropertyDescriptor
System.ComponentModel.DependencyPropertyDescriptor
System.ComponentModel.TypeConverter.SimplePropertyDescriptor
| Name | Description | |
|---|---|---|
![]() | PropertyDescriptor(MemberDescriptor) | Initializes a new instance of the PropertyDescriptor class with the name and attributes in the specified MemberDescriptor. |
![]() | PropertyDescriptor(MemberDescriptor, Attribute()) | 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()) | Initializes a new instance of the PropertyDescriptor class with the specified name and attributes. |
| Name | Description | |
|---|---|---|
![]() | AttributeArray | Gets or sets an array of attributes.(Inherited from MemberDescriptor.) |
![]() | Attributes | Gets the collection of attributes for this member.(Inherited from MemberDescriptor.) |
![]() | Category | Gets the name of the category to which the member belongs, as specified in the CategoryAttribute.(Inherited from MemberDescriptor.) |
![]() | ComponentType | When overridden in a derived class, gets the type of the component this property is bound to. |
![]() | Converter | Gets the type converter for this property. |
![]() | Description | Gets the description of the member, as specified in the DescriptionAttribute.(Inherited from MemberDescriptor.) |
![]() | DesignTimeOnly | Gets whether this member should be set only at design time, as specified in the DesignOnlyAttribute.(Inherited from MemberDescriptor.) |
![]() | DisplayName | Gets the name that can be displayed in a window, such as a Properties window.(Inherited from MemberDescriptor.) |
![]() | IsBrowsable | Gets a value indicating whether the member is browsable, as specified in the BrowsableAttribute.(Inherited from MemberDescriptor.) |
![]() | IsLocalizable | Gets a value indicating whether this property should be localized, as specified in the LocalizableAttribute. |
![]() | IsReadOnly | When overridden in a derived class, gets a value indicating whether this property is read-only. |
![]() | Name | Gets the name of the member.(Inherited from MemberDescriptor.) |
![]() | NameHashCode | Gets the hash code for the name of the member, as specified in GetHashCode.(Inherited from MemberDescriptor.) |
![]() | PropertyType | When overridden in a derived class, gets the type of the property. |
![]() | SerializationVisibility | Gets a value indicating whether this property should be serialized, as specified in the DesignerSerializationVisibilityAttribute. |
![]() | SupportsChangeEvents | Gets a value indicating whether value change notifications for this property may originate from outside the property descriptor. |
| Name | Description | |
|---|---|---|
![]() | AddValueChanged(Object, EventHandler) | Enables other objects to be notified when this property changes. |
![]() | CanResetValue(Object) | When overridden in a derived class, returns whether resetting an object changes its value. |
![]() | CreateAttributeCollection() | Creates a collection of attributes using the array of attributes passed to the constructor.(Inherited from MemberDescriptor.) |
![]() | CreateInstance(Type) | Creates an instance of the specified type. |
![]() | Equals(Object) | Compares this to another object to see if they are equivalent.(Overrides MemberDescriptor.Equals(Object).) |
![]() | FillAttributes(IList) | Adds the attributes of the PropertyDescriptor to the specified list of attributes in the parent class.(Overrides MemberDescriptor.FillAttributes(IList).) |
![]() | Finalize() | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.) |
![]() | GetChildProperties() | Returns the default PropertyDescriptorCollection. |
![]() | GetChildProperties(Attribute()) | Returns a PropertyDescriptorCollection using a specified array of attributes as a filter. |
![]() | GetChildProperties(Object) | Returns a PropertyDescriptorCollection for a given object. |
![]() | GetChildProperties(Object, Attribute()) | Returns a PropertyDescriptorCollection for a given object using a specified array of attributes as a filter. |
![]() | GetEditor(Type) | Gets an editor of the specified type. |
![]() | GetHashCode() | Returns the hash code for this object.(Overrides MemberDescriptor.GetHashCode().) |
![]() | GetInvocationTarget(Type, Object) | This method returns the object that should be used during invocation of members.(Overrides MemberDescriptor.GetInvocationTarget(Type, Object).) |
![]() | GetType() | |
![]() | GetTypeFromName(String) | Returns a type using its name. |
![]() | GetValue(Object) | When overridden in a derived class, gets the current value of the property on a component. |
![]() | GetValueChangedHandler(Object) | Retrieves the current set of ValueChanged event handlers for a specific component |
![]() | MemberwiseClone() | |
![]() | OnValueChanged(Object, EventArgs) | Raises the ValueChanged event that you implemented. |
![]() | RemoveValueChanged(Object, EventHandler) | Enables other objects to be notified when this property changes. |
![]() | ResetValue(Object) | When overridden in a derived class, resets the value for this property of the component to the default value. |
![]() | SetValue(Object, Object) | When overridden in a derived class, sets the value of the component to a different value. |
![]() | ShouldSerializeValue(Object) | When overridden in a derived class, determines a value indicating whether the value of this property needs to be persisted. |
![]() | ToString() | Returns a string that represents the current object.(Inherited from Object.) |
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 provides the following properties and methods:
Converter contains the TypeConverter for this property.
IsLocalizable indicates whether this property should be localized.
GetEditor returns an editor of the specified type.
PropertyDescriptor also provides the following abstract properties and methods:
ComponentType contains the type of component this property is bound to.
IsReadOnly indicates whether this property is read-only.
PropertyType gets the type of the property.
CanResetValue indicates whether resetting the component changes the value of the component.
GetValue returns the current value of the property on a component.
ResetValue resets the value for this property of the component.
SetValue sets the value of the component to a different value.
ShouldSerializeValue indicates whether the value of this property needs to be persisted.
Typically, the abstract members are implemented through reflection. For more information about reflection, see the topics in Reflection in the .NET Framework.
The following code example is built upon the example in the PropertyDescriptorCollection class. It prints the information (category, description, display name) of the text of a button in a text box. It assumes that button1 and textbox1 have been instantiated on a form.
' 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
The following code example shows how to implement a custom property descriptor that provides a read-only wrapper around a property. The SerializeReadOnlyPropertyDescriptor is used in a custom designer to provide a read-only property descriptor for the control's Size property.
Imports System 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 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
The following code examples show how to use the The SerializeReadOnlyPropertyDescriptor in a custom designer.
Imports System 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
Available since 1.1
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Any public static ( Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.



