Hi Robert,

ICustomTypeDescriptor is not required.  You can create a custom TypeConverter that will provide your object dynamic properties at
runtime to be used by a PropertyGrid:   Derive a class from System.ComponentModel.PropertyDescriptor to encapsulate your 'dynamic'
properties.

Here's an example of a custom TypeConverter you can use for an object name CustomObject:

public class CustomObjectTypeConverter : ExpandableObjectConverter
// ExpandableObjectConverter allows and instance of an object to which the
// CustomObjectTypeConverter class is applied using the TypeConverterAttribute
// to be expandable in the PropertyGrid when used as the Type of a property
// for another class.
{
 public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
 {
  if (destinationType == typeof(string))
   return true;

  return base.CanConvertTo (context, destinationType);
 }

 public override object ConvertTo(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value, Type
destinationType)
 {
  if (context == null)
   throw new ArgumentNullException("context");

  if (value is CustomObject && destinationType == typeof(string))
   // this is the string value displayed in the PropertyGrid for an expandable object (+)
   return string.Format("[{0}]", context.PropertyDescriptor.DisplayName);

  return base.ConvertTo (context, culture, value, destinationType);
 }

 public override bool GetPropertiesSupported(ITypeDescriptorContext context)
 {
  if (context == null || !(context.Instance is CustomObject))
   return base.GetPropertiesSupported(context);

  return true;
 }

 public override PropertyDescriptorCollection GetProperties(ITypeDescriptorContext context, object value, Attribute[] attributes)
 {
  CustomObject owner = value as CustomObject;

  if (owner == null)
   return base.GetProperties(context, value, attributes);

   // return value declared here, filled in the foreach loop below
  PropertyDescriptorCollection props = new PropertyDescriptorCollection(null);

   // this line simply creates a collection of custom PropertyDescriptor objects
   // for the owner (CustomObject).
  CustomObjectDynamicProperties[] dynamicProps = owner.GetDynamicProperties();

  foreach (PropertyDescriptor prop in dynamicProps)
  {
       // PropertyGrid doesn't check IsBrowsable for dynamic properties
       // so you'll have to check that yourself:
       if (prop != null && !prop.Attributes.Matches(new BrowsableAttribute(false)))
            // Add the option
            props.Add(prop);
  }

  return props;
 }
}