Is Func appropriate to use as a ctor arg when applying Dependency Injection?

Question

Example:

public class BusinessTransactionFactory  where T : IBusinessTransaction
{
    readonly Func _createTransactio         


        

Answer 1

I think the real question here is whether the dependency type should be considered a contract.

In the case of a Func delegate, you are declaring a dependency on a certain method structure, but nothing more. You cannot deduce the range of accepted input values (pre-conditions), constraints on the expected output (post-conditions), or what they mean exactly by looking at this structure. For example, is null an acceptable return value? And if it is, then how should it be interpreted?

In the case of an interface, you have a contract agreed upon by both parties: the consumer explicitly declares that it needs a particular interface, and the implementer explicitly declares to provide it. This goes beyond structure: the documentation of the interface will talk about the pre-conditions, post-conditions and semantics.