I have a custom property type called CustomPropertyType1, which inherits from PropertyLongString.

The result of adding this property in a composer class, that inherits from BaseComposerFunctionData as follows:

[PageTypeProperty(
            EditCaption = "Caption here",
            HelpText = "Help text here",
            Type = typeof(CustomPropertyType1),
            Required = true)]
        public virtual string Property1 { get; set; }
        
is that, when editing that composer class in the UI, I have a list of checkboxes with all the values I'd expect (some text values).

Now, if from another context, non composer, namely a regular ascx, I attempt var x = new CustomPropertyType1() the result is a null.

Is this a syntax problem?