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11/17/2011

Type.GetDefaultMembers Method

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Searches for the members defined for the current Type whose DefaultMemberAttribute is set.

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

Syntax

'Declaration
Public Overridable Function GetDefaultMembers As MemberInfo()

public virtual MemberInfo[] GetDefaultMembers()

Return Value

Type: array<System.Reflection.MemberInfo[]
An array of MemberInfo objects representing all default members of the current Type.
-or-
An empty array of type MemberInfo, if the current Type does not have default members.

Remarks

The GetDefaultMembers method does not return members in a particular order, such as alphabetical or declaration order. Your code must not depend on the order in which members are returned, because that order varies.

This method can be overridden by a derived class.

Members include properties, methods, fields, events, and so on.

The following table shows what members of a base class are returned by the Get methods when reflecting on a type.

Member Type	Static	Non-Static
Constructor	No	No
Field	No	Yes. A field is always hide-by-name-and-signature.
Event	Not applicable	The common type system rule is that the inheritance is the same as that of the methods that implement the property. Reflection treats properties as hide-by-name-and-signature. See note 2 below.
Method	No	Yes. A method (both virtual and non-virtual) can be hide-by-name or hide-by-name-and-signature.
Nested Type	No	No
Property	Not applicable	The common type system rule is that the inheritance is the same as that of the methods that implement the property. Reflection treats properties as hide-by-name-and-signature. See note 2 below.

Notes:

Hide-by-name-and-signature considers all of the parts of the signature, including custom modifiers, return types, parameter types, sentinels, and unmanaged calling conventions. This is a binary comparison.
For reflection, properties and events are hide-by-name-and-signature. If you have a property with both a get and a set accessor in the base class, but the derived class has only a get accessor, the derived class property hides the base class property, and you will not be able to access the setter on the base class.
Custom attributes are not part of the common type system.

If the current Type represents a constructed generic type, this method returns the MemberInfo objects with the type parameters replaced by the appropriate type arguments. For example, if class C<T> has a property P that returns T, calling GetDefaultMembers on C<int> returns int P in C# (Property P As Integer in Visual Basic).

If the current Type represents a type parameter in the definition of a generic type or generic method, this method searches the members of the class constraint, or the members of Object if there is no class constraint.

Examples

The following example obtains the default member information of MyClass and displays the default members.

Note:
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control.

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.

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