Specifications for modern C# · zero third-party dependencies

Business rules that read like business rules.

Compose named rules with terse, discoverable syntax—then evaluate them in memory or hand them to infrastructure without leaking a query API.

NuGet · latestdotnet add package DanMarshall.FluentSpecifications

OrderSearch.csNo IQueryable

var request = Order.Search
    .Matching.CanShip.And.HighPriority
    .Sorted.By.CreatedAt.Desc
    .Then.By.Id.Asc
    .Page(2).OfSize(50);

Informed by the internal Kotlin API used at Reapit and established specification libraries across C#, Java, Kotlin, TypeScript, and PHP.

A deliberately small idea

Readable at the call site. Honest at the boundary.

`CanShip.And.HighPriority` says what the rule means without ceremony or overloaded Boolean operators.

The same immutable specification supports fast matching, structured diagnostics, rendering, and translation.

Rules and immutable searches cross the boundary. EF Core stays in infrastructure and materializes results before returning.

The useful boundary

A specification stays Boolean. A separate immutable search can add sorting and paging without leaking EF, `DbSet`, or `IQueryable`.