Node.AsPropertyDescriptor.CanResetValue

I've tried to implement Reset button on the PropertyGrid and I have the following exception in this code:

System.NotImplementedException occurred
Message="The method or operation is not implemented."
Source="Mindscape.WpfPropertyGrid"
StackTrace:
    at #c.#ip.CanResetValue(Object component)
    at PropertyGridDemo.MainWindow.CommandBinding_CanExecute(Object sender, CanExecuteRoutedEventArgs e) in …

How I can implement a Reset button (for resetting property values)? May be, it is a good idea for implement this functionality by PropertyGrid naturally? ;о)

I assume you are talking about a multiple selection scenario?  In that case, send the ManyEditor.ResetCommand with a parameter of the edited object:

<Button Command="{x:Static local:ManyEditor.ResetCommand}" CommandParameter="{Binding}" />

And bind the command to handlers such as these:

private void ResetCommand_CanExecute(object sender, CanExecuteRoutedEventArgs e)
{
  ObjectWrapper ow = (ObjectWrapper)(e.Parameter);
  if (ow == null)
  {
    e.CanExecute = false;
  }
  else
  {
    try
    {
      Many many = (Many)(ow.RawValue);
      e.CanExecute = !many.IsReadOnly;
    }
    catch (ArgumentNullException)
    {
      e.CanExecute = false;
    }
  }
}

private void ResetCommand_Executed(object sender, ExecutedRoutedEventArgs e)
{
  ObjectWrapper ow = (ObjectWrapper)(e.Parameter);
  Many many = (Many)(ow.RawValue);
  many.Reset();
}

Alternatively, if you are implementing your own command which will receive a PropertyGridRow, as shown in your sample code, cast row.Node.Value to Many, and call Reset on the resulting Many.