Update README.md

README.md

@@ -53,6 +53,8 @@ Base class with tests for adding specifications to a DDD model. Also includes a
 
 - Implement infrastructure for specification validators. [Issue #111](https://github.com/ardalis/Specification/issues/111)
 
+- `GetBySpecAsync` and similar methods are marked obsolete; prefer `FirstOrDefault` or `SingleOrDefault` instead.
+
 ## Sample Usage
 
 The Specification pattern pulls query-specific logic out of other places in the application where it currently exists. For applications with minimal abstraction that use EF Core directly, the specification will eliminate `Where`, `Include`, `Select` and similar expressions from almost all places where they're being used. In applications that abstract database query logic behind a `Repository` abstraction, the specification will typically eliminate the need for many custom `Repository` implementation classes as well as custom query methods on `Repository` implementations. Instead of many different ways to filter and shape data using various methods, the same capability is achieved with few core methods.