Getting EntryPointNotFoundException on ditto objects

[Andy Jenkins]

I've been running into this issue erratically on several sites I work on, and I just now traced it down to Ditto.

I've got a data type in Umbraco called Common Link. It's an Archetype, with several different fieldset types available. I created models for each of these fieldset types, and all of them implement an interface named ICommonLink.

One of the properties on ICommonLink is this:
bool IsAnchor { get; }

This property is for future use, so on all the classes which implement ICommonLink, I've implemented this property like this:
public bool IsAnchor => true;

I'm mapping these Archetype models into variables of type ICommonLink, which usually works with no issue. However, in one particular situation I'm consistently getting this error:

When I debugged this application, my debugger stopped on the exact line shown in the screenshot. I ran "link.GetType()" in the immediate window, and saw VS report that the "link" variable is an ArchetypeFieldSetModel, not something that implements ICommonLink.

I'm not familiar with the flavor of magic that Ditto uses under the hood to make everything work, but here's what I think is happening: I think normally, Ditto uses reflection to enumerate properties on types and listen for requests to those properties, so that it can defer conversion until they're actually used. I think that the C# compiler takes some kind of shortcut on constant-value properties such as I'm using, which results in Ditto not seeing the property, and therefore not intercepting requests for that property. When I access other properties first, this issue doesn't occur, because those properties trigger Ditto Processing, after which the variable contains the expected object type.

[Nicholas-Westby]

Some version information for extra context:

• Umbraco 7.12.3
• Ditto 0.12.2

Also, I'm not sure which model Andy is working with, but he's most likely using [DittoMixedArchetype] from here: https://github.com/rhythmagency/rhythm.umbraco.ditto.archetype/blob/master/src/Rhythm.Umbraco.Ditto.Archetype/Processors/DittoMixedArchetypeAttribute.cs

That will choose the appropriate class to instantiate depending on the Archetype fieldset alias (e.g., content link, media link, external link, and so on).

And if it's a single link rather than several, it may also be getting used in combination with [DittoFirstItem] from here: https://github.com/rhythmagency/rhythm.umbraco.ditto/blob/master/src/Rhythm.Umbraco.Ditto/Processors/DittoFirstItemAttribute.cs

[Andy Jenkins]

he's most likely using [DittoMixedArchetype]

... well, he thought he was. Turns out, he wasn't.

Sorry! This came down to me not putting the correct processors on a property.