[mythz]

You never need to drop down into free form expressions to satisfy a query which should never be exposed over a service boundary, this is a very clear Services anti-pattern introducing unnecessary coupling. Find which requirements your Service needs to implement and expose them under the most intuitive self-descriptive label for end users, if you need Orders after a certain date you can expose `?createdAfter=...` or `createdBefore=...`, `?createdAt=...`, etc.

There's nothing in OData that cannot be done more simply and elegantly without it, if you wan't auto querying check out the approach used in: https://github.com/ServiceStack/ServiceStack/wiki/Auto-Query

It's cleaner, faster, more interoperable and it's implementation is fully substitutable, supporting multiple data sources over a user configurable Surface Area that as it's just the same as any other ServiceStack Service has access to all its existing features it enables for all Services including support for an end-to-end typed API over multiple data formats, that's able to take advantage of existing metadata services, and also includes an optional AutoQuery UI. Because it's just another Service there's also infinitely less incremental knowledge to learn whilst at the same time being able to take advantage of features of existing Services Users already know.

This is just one approach, most people never need the inherent complexity and ridgity in big heavy fx's like OData which used to have traction when MS had all its marketing momentum behind it but it's hey day is over and abandoned by its high profile early adopters, now it just lingers in maintenance-mode, mostly forgotten outside of MS and held on by the few that haven't moved on.