New Post: PropertyGrid with object implementing ICustomTypeConverter to add extra properties

If you utilise ICustomTypeConverter to add extra properties on an object, the PropertyGrid does not correctly use ICustomTypeConverter.GetPropertyOwner(). I believe that this is because in CreatePropertyItem() assumes SelectedObject is the correct instance, where it should be requesting the object instance using code similar to:

        public object GetValueInstance(object sourceObject)
        {
            ICustomTypeDescriptor customTypeDescriptor = sourceObject as ICustomTypeDescriptor;
            if (customTypeDescriptor != null)
                sourceObject = customTypeDescriptor.GetPropertyOwner(PropertyDescriptor);

            return sourceObject;
        }

For example, if you have the following the property grid will generate an error:

    public class TestSubClass
    {
        public string ExtendedField { get; set; }
    }

    public class TestClass : ICustomTypeDescriptor
    {
        public TestClass()
        {

        }
        public string Name { get; set; }

        [Browsable(false)]
        public TestSubClass SubInfo { get; set; }

        #region ICustomTypeDescriptor implementation

        #region Standard implementation

        AttributeCollection ICustomTypeDescriptor.GetAttributes()
        {
            return TypeDescriptor.GetAttributes(this, true);
        }

        string ICustomTypeDescriptor.GetClassName()
        {
            return TypeDescriptor.GetClassName(this, true);
        }

        string ICustomTypeDescriptor.GetComponentName()
        {
            return TypeDescriptor.GetComponentName(this, true);
        }

        TypeConverter ICustomTypeDescriptor.GetConverter()
        {
            return TypeDescriptor.GetConverter(this, true);
        }

        EventDescriptor ICustomTypeDescriptor.GetDefaultEvent()
        {
            return TypeDescriptor.GetDefaultEvent(this, true);
        }

        PropertyDescriptor ICustomTypeDescriptor.GetDefaultProperty()
        {
            return TypeDescriptor.GetDefaultProperty(this, true);
        }

        object ICustomTypeDescriptor.GetEditor(Type editorBaseType)
        {
            return TypeDescriptor.GetEditor(this, editorBaseType, true);
        }

        EventDescriptorCollection ICustomTypeDescriptor.GetEvents(Attribute[] attributes)
        {
            return TypeDescriptor.GetEvents(this, attributes, true);
        }

        EventDescriptorCollection ICustomTypeDescriptor.GetEvents()
        {
            return TypeDescriptor.GetEvents(this, true);
        }
        #endregion

        #region Custom implmenetation
        PropertyDescriptorCollection ICustomTypeDescriptor.GetProperties(Attribute[] attributes)
        {
            return GetCombinedProperties(attributes);
        }

        PropertyDescriptorCollection ICustomTypeDescriptor.GetProperties()
        {
            return GetCombinedProperties(null);
        }

        PropertyDescriptorCollection GetCombinedProperties(Attribute[] attributes)
        {
            PropertyDescriptorCollection ourPropsCollection = TypeDescriptor.GetProperties(this, attributes, true);
            List<PropertyDescriptor> ourProps = new List<PropertyDescriptor>();
            foreach (PropertyDescriptor prop in ourPropsCollection)
                ourProps.Add(prop);

            if (SubInfo == null)
                SubInfo = new TestSubClass();

            if (SubInfo != null)
            {
                PropertyDescriptorCollection setProps = TypeDescriptor.GetProperties(SubInfo, attributes, true);
                if (setProps != null)
                {
                    foreach (PropertyDescriptor prop in setProps)
                    {
                       ourProps.Add(prop);
                    }
                }
            }
            return new PropertyDescriptorCollection(ourProps.ToArray());
        }

        object ICustomTypeDescriptor.GetPropertyOwner(PropertyDescriptor pd)
        {
            PropertyDescriptorCollection props = TypeDescriptor.GetProperties(this, true);
            if (props.Contains(pd))
                return this;
            else
                return SubInfo;
        }
        #endregion

        #endregion ICustomTypeDescriptor implementation
    }