External List from External Content Type: missing and/or error

Question

I've created an ECT w/ Read List and Read Item operations using SharePoint Designer, saved it, and given myself permissions. The ECT's external data source is a WCF service.

When I try to create an External List using the browser, the ECT does not appear in the External Content Type Picker.

When I try to create an External List from the ECT in SharePoint Designer, I'm shown the following error:

Could not save changes. No Finders available in the View Group associated with the SpecificFinder (Read Item) operation 'FindWidget' on Entity (External Content Type) with Namespace = 'http://widgetserver', Name = 'Widgets'. The list cannot be created.

How can I create an External List based on my ECT?

Answer 1

My ECT's Read List and Read Item operations returned columns whose type were complex. Once I changed the return columns to all be simple/native/value types, I was able to create an External List based on my ECT in either the browser or SharePoint Designer.