[Medium] Specification interface

SpecificationInterface.cs

// implenation details omitted intentionally

public sealed class Specification<TSource>
{
    // for expression based APIs
    public Expression<Func<TSource, bool>> IsSatisfiedByExpression { get; }

    // for regular code
    public Func<TSource, bool> IsSatisfiedBy { get; }

    // create specification from expression 
    public Specification(Expression<Func<TSource, bool>> expressionFunc)

    // create specification from expression and delegate
    public Specification(Expression<Func<TSource, bool>>? expressionFunc, Func<TSource, bool> delegateFunc)

    // combination support: combinedSpec = spec1 && spec2
    public static Specification<TSource> operator &(Specification<TSource> spec1, Specification<TSource> spec2)

    // combination support: combinedSpec = spec1 || spec2
    public static Specification<TSource> operator |(Specification<TSource> spec1, Specification<TSource> spec2)

    // false operator required to prevent short-circuit and force evaluate both specs: spec1 && spec2
    public static bool operator false(Specification<TSource> _) => false;

    // true operator used by if, while statements etc. required as pair to the false operator
    public static bool operator true(Specification<TSource> _) => false;

    // easy negation: negatedSpec = !somespec
    public static Specification<TSource> operator !(Specification<TSource> specification)

    // simplify usage by implicitly converting specification to Func<TSource, bool>
    public static implicit operator Func<TSource, bool>(Specification<TSource> f)

    //  simplify usage by implicitly converting specification to Expression<Func<TSource, bool>>
    public static implicit operator Expression<Func<TSource, bool>>(Specification<TSource> f)
}