Trying to read custom field from Dynamics CRM 2016 using Xrm.WebApi

Question

I want to read a custom field named (mxpcah_new_phonecalltype) using a WebApi call.

From my browser I can call: https://myurl/PhonecallActivityHistory/api/data/v8.2/activitypointers(CEA756CE-5D7E-EA11-A97E-005056B82894) and get:

this result does not include the aforementioned custom field.

Now I query: https://myurl/PhonecallActivityHistory/api/data/v8.2/activitypointers(CEA756CE-5D7E-EA11-A97E-005056B82894)?$expand=activitypointer_activity_parties($select=participationtypemask,addressused)

Now I see:

I am sure that my test activity has a value set for the custom field:

I have made sure that this value is saved to the activity. Hit save button on the bottom right. Closed the browser window. reopend the browser and selected the activity to make sure the data is stored to the field

The custom field is defined as follows:

So I would have expected to be 100000002 instead of null. Any idea why I can't read the custom field?

Also I took into account this resource: https://community.dynamics.com/crm/f/microsoft-dynamics-crm-forum/350873/doesn-t-xrm-webapi-support-custom-fields/937811 I copy and pasted the custom schema name and made sure it is written correctly. More info on the Api is found here: https://learn.microsoft.com/de-de/powerapps/developer/common-data-service/webapi/retrieve-entity-using-web-api#retrieve-specific-properties

Answer 1

Activity (activitypointer) is a container entity which will have all the OOB common attributes from across the different activity records like email, phonecall, fax, etc

Activity party is the container for associated attendees records like email sender, meeting participants, phonecall receivers, etc

So web api calls targeting either of the above will not give you the custom attributes which you created in specific activity type. ie phonecall

Instead try this:

https://crmdev.crm.dynamics.com/api/data/v9.1/phonecalls

https://myurl/PhonecallActivityHistory/api/data/v8.2/phonecalls(CEA756CE-5D7E-EA11-A97E-005056B82894)