All I was talking about was getting the valueconstraint from the editor and then creating one if its null. To take your original snippet:

private static void OnNumberRspParamChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
  NumberRspParam numberRspParam = e.NewValue as NumberRspParam;

  if (numberRspParam != null)
  {
    ValueEditor editor = d as ValueEditor;
    ValueConstraint constraint = editor.ValueConstraint;
    if (constraint == null)
      editor.ValueConstraint = constraint = new ValueConstraint();
    constraint.SetValue(ValueConstraint.MaxInclusiveProperty, numberRspParam.MaxValue);
    constraint.SetValue(ValueConstraint.MinInclusiveProperty, numberRspParam.MinValue);
  }
}

Man, an example would be WONDERFUL.  I think I need to do the following, but I don't have a clue to where it should be assigned:

????????? = DependencyProperty.RegisterAttached("ValueConstraint", typeof(ValueConstraint), typeof(UdaNumericEditor));

I have tried adding the property to my class and registering it in my constructor, but when I try to get the value, it doesn't work:

public static readonly DependencyProperty ValueConstraintProperty;

public static readonly DependencyProperty NumberRspParamProperty;

static UdaNumericEditor()

{

    ValueConstraintProperty = DependencyProperty.RegisterAttached("ValueConstraint", 

        typeof(ValueConstraint), typeof(UdaNumericEditor));

    NumberRspParamProperty = DependencyProperty.Register("NumberRspParam",

        typeof(NumberRspParam), typeof(UdaNumericEditor),

        new FrameworkPropertyMetadata(OnNumberRspParamChanged));

    //FrameworkPropertyMetadata metadata = new FrameworkPropertyMetadata(

    //    FrameworkPropertyMetadataOptions.None, new PropertyChangedCallback(OnCurrentReadingChanged));

    CommandManager.RegisterClassCommandBinding(typeof(UdaNumericEditor),

        new CommandBinding(ApplicationCommands.Paste, null));

}

private static void OnNumberRspParamChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

{

    NumberRspParam numberRspParam = e.NewValue as NumberRspParam;

    if (numberRspParam != null)

    {

        object o = d.GetValue(ValueEditor.ValueConstraintProperty);

        ValueConstraint valueConstraint = o as ValueConstraint;

        d.SetValue(Infragistics.Windows.Editors.ValueConstraint.MaxInclusiveProperty, numberRspParam.MaxValue);

        d.SetValue(Infragistics.Windows.Editors.ValueConstraint.MinInclusiveProperty, numberRspParam.MinValue);

    }

}

It would be null if you never set the ValueConstraint property in which case maybe you want to create one if it returns null.

I understand the concept, but cannot figure out exactly how to get the ValueContraint from the control.  So far this is my best guess and it always returns null.  Any suggestions?

object valueConstraintProperty = d.GetValue(ValueEditor.ValueConstraintProperty);