.NET Framework Class Library
DefaultEventAttribute Class

Updated: November 2007

Specifies the default event for a component.

Namespace:  System.ComponentModel
Assembly:  System (in System.dll)

Visual Basic (Declaration)
<AttributeUsageAttribute(AttributeTargets.Class)> _
Public NotInheritable Class DefaultEventAttribute _
    Inherits Attribute
Visual Basic (Usage)
Dim instance As DefaultEventAttribute
C#
[AttributeUsageAttribute(AttributeTargets.Class)]
public sealed class DefaultEventAttribute : Attribute
Visual C++
[AttributeUsageAttribute(AttributeTargets::Class)]
public ref class DefaultEventAttribute sealed : public Attribute
J#
/** @attribute AttributeUsageAttribute(AttributeTargets.Class) */
public final class DefaultEventAttribute extends Attribute
JScript
public final class DefaultEventAttribute extends Attribute

Use the Name property to get the name of the default event.

For more information, see Attributes Overview and Extending Metadata Using Attributes.

The following example defines a collection class named MyCollection. The class is marked with a DefaultEventAttribute that specifies CollectionChanged as the default event.

Visual Basic
<DefaultEvent("CollectionChanged")> _ 
Public Class MyCollection
    Inherits BaseCollection

    Public Event CollectionChanged (ByVal sender As Object, _
        ByVal e As CollectionChangeEventArgs)

    ' Insert additional code.
End Class 'MyCollection

C#
[DefaultEvent("CollectionChanged")]
public class MyCollection : BaseCollection {

    private CollectionChangeEventHandler onCollectionChanged;

    public event CollectionChangeEventHandler CollectionChanged {
       add {
          onCollectionChanged += value;
       }
       remove {
          onCollectionChanged -= value;
       }
    }
    // Insert additional code.
}

Visual C++
[DefaultEvent("CollectionChanged")]
public ref class TestCollection: public BaseCollection
{
private:
    CollectionChangeEventHandler^ onCollectionChanged;

public:
    event CollectionChangeEventHandler^ CollectionChanged 
    {
    public:
        void add(CollectionChangeEventHandler^ eventHandler)
        { 
            onCollectionChanged += eventHandler; 
        }

    protected:
        void remove(CollectionChangeEventHandler^ eventHandler) 
        { 
            onCollectionChanged -= eventHandler; 
        }
    }
    // Insert additional code.
};

J#
/** @attribute DefaultEvent("CollectionChanged")
 */
public static class MyCollection extends BaseCollection
{
    private CollectionChangeEventHandler onCollectionChanged;

    public void add_onCollectionChanged(CollectionChangeEventHandler value)
    {
        onCollectionChanged = (CollectionChangeEventHandler)
            System.Delegate.Combine(onCollectionChanged, value);
    }

    public void remove_onCollectionChanged(CollectionChangeEventHandler
        value)
    {
        onCollectionChanged = (CollectionChangeEventHandler)
            System.Delegate.Remove(onCollectionChanged, value);
    }
    // Insert additional code.
} //MyCollection

The next example creates an instance of MyCollection. Then it gets the attributes for the class, extracts the DefaultEventAttribute, and prints the name of the default event.

Visual Basic
Public Shared Function Main() As Integer
    ' Creates a new collection.
    Dim myNewCollection As New MyCollection()

    ' Gets the attributes for the collection.
    Dim attributes As AttributeCollection = TypeDescriptor.GetAttributes(myNewCollection)

    ' Prints the name of the default event by retrieving the
    ' DefaultEventAttribute from the AttributeCollection. 
    Dim myAttribute As DefaultEventAttribute = _
        CType(attributes(GetType(DefaultEventAttribute)), DefaultEventAttribute)
    Console.WriteLine(("The default event is: " & myAttribute.Name))
    Return 0
End Function 'Main

C#
public static int Main() {
    // Creates a new collection.
    MyCollection myNewCollection = new MyCollection();

    // Gets the attributes for the collection.
    AttributeCollection attributes = TypeDescriptor.GetAttributes(myNewCollection);

    /* Prints the name of the default event by retrieving the 
     * DefaultEventAttribute from the AttributeCollection. */
    DefaultEventAttribute myAttribute = 
       (DefaultEventAttribute)attributes[typeof(DefaultEventAttribute)];
    Console.WriteLine("The default event is: " + myAttribute.Name);
    return 0;
 }

Visual C++
int main()
{
    // Creates a new collection.
    DefaultEventAttributeExample::TestCollection^ newCollection = 
        gcnew DefaultEventAttributeExample::TestCollection;

    // Gets the attributes for the collection.
    AttributeCollection^ attributes = 
        TypeDescriptor::GetAttributes(newCollection);

    // Prints the name of the default event by retrieving the 
    // DefaultEventAttribute from the AttributeCollection.
    DefaultEventAttribute^ attribute = (DefaultEventAttribute^)
        attributes[DefaultEventAttribute::typeid];
    Console::WriteLine("The default event is: {0}", attribute->Name);
}

J#
public static void main(String[] args)
{
    // Creates a new collection.
    MyCollection myNewCollection = new MyCollection();
    // Gets the attributes for the collection.
    AttributeCollection attributes = TypeDescriptor.
        GetAttributes(myNewCollection);

    /* Prints the name of the default event by retrieving the 
     * DefaultEventAttribute from the AttributeCollection. */
    DefaultEventAttribute myAttribute = (DefaultEventAttribute)attributes.
        get_Item(DefaultEventAttribute.class.ToType());
    Console.WriteLine("The default event is: " + myAttribute.get_Name());
} //main

System..::.Object
  System..::.Attribute
    System.ComponentModel..::.DefaultEventAttribute
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
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