This example implements something like P-Invoke, but it calls database stored procedures instead of native functions.

Methods have to be defined as extern like this:

[MethodImpl(MethodImplOptions.InternalCall)]
public extern IEnumerable<Speaker> GetActiveSpeakers();

In this design, methods must be instance (non-static) and declared in a class derived from BaseDpApi. This base class defined the Connection and Transaction properties used by the aspect.

The StoredProcedureAttribute class is the implementation of the aspect itself. It is applied to the BaseDbApi class with inheritance and multicast enabled, so any extern method in a derived class will be turned into a stored procedure call.

The MethodImpl thing is ugly but unfortunately required if we want to use extern methods. Other designs are possible, such as providing a dummy implementation for the method.

To test this sample, you must create a SQL database, load CreateDb.sql, and change the connection string in Program.Main.

This code is given for inspiration. A production-ready implementation should add error handling, test mapping of parameter types, implement out parameters, and so on.