AttributeProviderAttribute Class

Definition

Namespace:

System.ComponentModel

Assembly:

System.ComponentModel.TypeConverter.dll

Source:

AttributeProviderAttribute.cs

Enables attribute redirection. This class cannot be inherited.

public ref class AttributeProviderAttribute : Attribute

[System.AttributeUsage(System.AttributeTargets.Property)]
public class AttributeProviderAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.Property)>]
type AttributeProviderAttribute = class
    inherit Attribute

Public Class AttributeProviderAttribute
Inherits Attribute

Inheritance

Object

Attribute

AttributeProviderAttribute

Attributes

AttributeUsageAttribute

Examples

The following code example demonstrates using AttributeProviderAttribute to mark a DataSource property with a specific type of IListSource. For a full code listing, see How to: Apply Attributes in Windows Forms Controls.

[Category("Data")]
[Description("Indicates the source of data for the control.")]
[RefreshProperties(RefreshProperties.Repaint)]
[AttributeProvider(typeof(IListSource))]
public object DataSource
{
    get
    {
        return this.dataGridView1.DataSource;
    }

    set
    {
        this.dataGridView1.DataSource = value;
    }
}

<Category("Data"), _
Description("Indicates the source of data for the control."), _
RefreshProperties(RefreshProperties.Repaint), _
AttributeProvider(GetType(IListSource))> _
Public Property DataSource() As Object
    Get
        Return Me.dataGridView1.DataSource
    End Get

    Set(ByVal value As Object)
        Me.dataGridView1.DataSource = value
    End Set
End Property

Remarks

There are a few cases in the .NET Framework object model where a property is purposely typed to be vague. For example, the DataGridView.DataSource property is typed as object. The reason for this is that this property can accept several types of input. Unfortunately, this provides no common place to add metadata to describe the characteristics of the property. Each DataSource property throughout the .NET Framework needs to have identical metadata for type converters, UI type editors, and other services that require metadata. The AttributeProviderAttribute remedies this situation.

Once this attribute is placed on a property, the rules for obtaining attributes for the property descriptor's MemberDescriptor.Attributes collection differ. Typically, the property descriptor gathers local attributes, and then merges these with attributes from the property type. In this case, the attributes are taken from the type returned from the AttributeProviderAttribute, not from the actual property type. This attribute is used on DataGridView.DataSource to point the DataGridView.DataSource object's specific type to IListSource, and the appropriate metadata is placed on IListSource to enable data binding. In so doing, external parties can easily add metadata to all data sources.

Attributes obtained from a type declared in the AttributeProviderAttribute have a priority in between the attributes of the property's type and the attributes on the property. The following list, in priority order, shows the full set of available merged attributes:

• Property Attributes

• Attribute Provider Attributes

• Property Type Attributes

Constructors

AttributeProviderAttribute(String, String)	Initializes a new instance of the AttributeProviderAttribute class with the given type name and property name.
AttributeProviderAttribute(String)	Initializes a new instance of the AttributeProviderAttribute class with the given type name.
AttributeProviderAttribute(Type)	Initializes a new instance of the AttributeProviderAttribute class with the given type.

Properties

PropertyName	Gets the name of the property for which attributes will be retrieved.
TypeId	When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute)
TypeName	Gets the assembly qualified type name passed into the constructor.

Methods

Equals(Object)	Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute)
GetHashCode()	Returns the hash code for this instance. (Inherited from Attribute)
GetType()	Gets the Type of the current instance. (Inherited from Object)
IsDefaultAttribute()	When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute)
Match(Object)	When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)

See also

• TypeDescriptor
• Type Descriptor Overview