Specification VS GuardClauses

If so, then look into this

Also, to minimize duplication of code and optimize your architecture i suggest using something like https://github.com/ardalis/Specification

This is a great candidate project for the Ardalis.Specifications library.

This is honestly such an amazing way to make sure you have a clear view of what your Linq does, see https://github.com/ardalis/Specification - note that the examples on the front git page uses a repository, but he later allowed the use directly on DbSet which finally made it possible for me to use the library.

Check out the specification pattern - it is designed to encapsulate query logic similar to your example. Steve Smith has a nice library for it on GitHub: https://github.com/ardalis/Specification

I'm thinking that the only way to abstract both of them would be to have the repositories return IEnumerables and have well defined aggregates for the entire application to avoid an exploding number of methods on the interface, but this is not possible in my project*. I've looked at Steve Smith's Specification library, but since it works with IQueryable, it would not work with Dapper.

You could also use the Ardalis Guard Clause, Ardalis Result and Fluent Validation

Here is an example how one would make sure our order total is valid. For this purpose I use an amazing library called GuardClauses.

GuardClauses

I'm guessing it's just a port of Ardalis' Guard class since he helped a lot with Microsoft's web projects.

The Guard Clauses are from: https://github.com/ardalis/GuardClauses

In terms of readability concerns, I definitely hear you on that. Using something like this can cut down on code bloat that comes with param validation and help with readability.

It's made by Ardalis, who wrote Microsoft's architectural guide for ASP.NET Core Web APIs. I like his GuardClauses library too.