使用来自EWS或REST API的office365 JS API访问CustomProperties

Question

I have an office 365 mail app that stores a value in a custom property before the item is saved. When the item is saved I want to access this property using a server-side application. Reading through the custom properties documentation tells me I can't access custom properties created using the JS API using any other service like EWS since these are not MAPI properties. Are there any workarounds ? Is it possible to access these using REST APIs ?

Answer 1

Actually, it is documented where they are stored and in what format. The [MS-OXCEXT] specification provides the specifics. Basically the values are stored as a JSON dictionary in a custom property on the item. You should be able to use EWS to read that custom property as an ExtendedProperty .

UPDATE: After discussing with folks internally, I should disclaim that this isn't a supported method as MrPiao indicated. As stated, the storage design could change, which would break your app if you depend on the current design. The concern is that I don't want to lead you down a path that eventually becomes unworkable :). If you can describe what your end goal is, perhaps we can suggest a more durable solution.

Answer 2

Custom Properties are definitely meant to be created and accessed only by Apps for Outlook APIs. However , this property has to get stored somewhere - and that's on the item. I'm fairly certain that if you made a GetItem call and enumerated every property on the item, you'll be able to access the custom props.

What's important to note is that this is most definitely an unsupported scenario . The design may change in the future, and this scenario may break. I would definitely not access custom properties outside a Mail App in a production setting.

Answer 3

Guid PS_PUBLIC_STRINGS = new Guid("00020329-0000-0000-C000-000000000046"); ////PS_PUBLIC_STRINGS' GUID
ExtendedPropertyDefinition extendedPropertyDefinition = new ExtendedPropertyDefinition(PS_PUBLIC_STRINGS, "cecp-{your add-in manifest id}", MapiPropertyType.String);
PropertySet psPropSet = new PropertySet() { extendedPropertyDefinition };

message.Load(psPropSet);