Multimedia schemas cause exception because they don't have a RootElementName

[DominicCronin]

tridion-practice/ChangeContentOrMetadata/CreateContentOrMetadata/CreateContentOrMetadata.cs

Line 36 in 74f53c5

content.AppendChild(content.CreateElement(string.IsNullOrEmpty(_rootElementName) ? _data.RootElementName : _rootElementName, _data.NamespaceUri));

If you attempt to instantiate Fields for a multimedia Schema/Component, there is no rootElementName for the content. So if you try to do something like this:

Fields.ForContentOf(schemaFields, _componentData);

you come out with a situation where _rootElementName and _data.RootElement name are both null, and CreateElement throws an exception.

[DominicCronin]

The question here is how best to fix it. Options might be:

1. Throw an argument exception if someone tries to instantiate Fields with a MMS/MMC. (It's usually frowned upon to throw from a constructor. )
2. Do the check in ForContentOf and return null (Might break client expectations of existing code that's already handling the exception)
3. Just don't call AppendChild in this situation. (Might leave the Fields object in an unexpected state)