Article
11/18/2011

DefaultMemberAttribute Class

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Defines the member of a type that is the default member used by InvokeMember.

Inheritance Hierarchy

System.Object
System.Attribute
System.Reflection.DefaultMemberAttribute

Namespace: System.Reflection
Assembly: mscorlib (in mscorlib.dll)

Syntax

'Declaration
<AttributeUsageAttribute(AttributeTargets.Class Or AttributeTargets.Struct Or AttributeTargets.Interface)> _
<ComVisibleAttribute(True)> _
Public NotInheritable Class DefaultMemberAttribute _
    Inherits Attribute

[AttributeUsageAttribute(AttributeTargets.Class|AttributeTargets.Struct|AttributeTargets.Interface)]
[ComVisibleAttribute(true)]
public sealed class DefaultMemberAttribute : Attribute

The DefaultMemberAttribute type exposes the following members.

Constructors

	Name	Description
	DefaultMemberAttribute	Initializes a new instance of the DefaultMemberAttribute class.

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Properties

	Name	Description
	MemberName	Gets the name from the attribute.

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Methods

	Name	Description
	Equals	Infrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Returns the hash code for this instance. (Inherited from Attribute.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	Match	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.)

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Remarks

A property is imported as an indexer (default indexed property in Visual Basic) if the property has arguments and if the name of the property or one of its accessors matches the name specified by the DefaultMemberAttribute. If the DefaultMemberAttribute is not present on the containing type, then the type does not have an indexer. The C# compiler emits the DefaultMemberAttribute on any type containing an indexer. In C# it is an error to manually attribute a type with the DefaultMemberAttribute if the type also declares an indexer.

Examples

The following example uses the DefaultMemberAttribute attribute to make the Age property the default member of the MyClass class.

Imports System.Reflection
Imports System.IO

<DefaultMemberAttribute("Age")> Public Class Example

   Public Sub Name(ByVal s As String)
   End Sub 'Name

   Public ReadOnly Property Age() As Integer
      Get
         Return 20
      End Get
   End Property

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Try
         Dim myType As Type = GetType([Example])
         Dim memberInfoArray As MemberInfo() = myType.GetDefaultMembers()
         If memberInfoArray.Length > 0 Then
            Dim memberInfoObj As MemberInfo
            For Each memberInfoObj In memberInfoArray
               outputBlock.Text &= "The default member name is: " + memberInfoObj.ToString() & vbCrLf
            Next memberInfoObj
         Else
            outputBlock.Text &= "No default members are available." & vbCrLf
         End If
      Catch e As InvalidOperationException
         outputBlock.Text &= "InvalidOperationException: " + e.Message & vbCrLf
      Catch e As IOException
         outputBlock.Text &= "IOException: " + e.Message & vbCrLf
      Catch e As Exception
         outputBlock.Text &= "Exception: " + e.Message & vbCrLf
      End Try
   End Sub 'Main
End Class '[MyClass]


using System;
using System.Reflection;
using System.IO;

[DefaultMemberAttribute("Age")]
public class Example
{
   public void Name(String s) { }
   public int Age
   {
      get
      {
         return 20;
      }
   }
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      try
      {
         Type myType = typeof(Example);
         MemberInfo[] memberInfoArray = myType.GetDefaultMembers();
         if (memberInfoArray.Length > 0)
         {
            foreach (MemberInfo memberInfoObj in memberInfoArray)
            {
               outputBlock.Text += "The default member name is: " + memberInfoObj.ToString() + "\n";
            }
         }
         else
         {
            outputBlock.Text += "No default members are available." + "\n";
         }
      }
      catch (InvalidOperationException e)
      {
         outputBlock.Text += "InvalidOperationException: " + e.Message + "\n";
      }
      catch (IOException e)
      {
         outputBlock.Text += "IOException: " + e.Message + "\n";
      }
      catch (Exception e)
      {
         outputBlock.Text += "Exception: " + e.Message + "\n";
      }
   }
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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