SpecificationPatternDotNet

An implementation of the Specification Pattern using idiomatic C#.

License

SpecificationPatternDotNet is licensed under the Microsoft Public License (MS-PL).

Getting Started

Install the SpecificationPatternDotNet package from NuGet.

Creating Specifications

Simply derive from Specification<TEntity> and override Predicate.

class GreaterThanSpecification : Specification<int>
{
    private readonly int _value;

    public GreaterThanSpecification(int value)
    {
        _value = value;
    }

    protected override Expression<Func<int, bool>> Predicate
    {
        get { return i => i > _value; }
    }
}

Using Specifications

Call SatisifiedBy on your specification to use it.

var entities = GetEntities();
var satisfiedEntities = compositeSpecification.SatisfiedBy(entities);

foreach (var entity in satisfiedEntities)
    Console.WriteLine("Found one! {0}", entity);

Combining Specifications

Specification<TEntity> contains AndAlso and OrElse methods for combining specifications.

var greaterThanSpecification = new GreaterThanSpecification(-2);
var lessThanSpecification = new LessThanSpecification(2);
var compositeSpecification = greaterThanSpecification.AndAlso(lessThanSpecification);

The True and False methods create an instance of Specification<TEntity> that can serve as useful starting points for combining specifications.

var specifications = GetSpecifications();
var allSpecifications = Specification<int>.True();

foreach (var specification in specifications)
    allSpecifications = allSpecifications.AndAlso(specification);

The Not method can be used to take the inverse of a specification.

Miscellany

SpecificationPatternDotNet targets .NET Standard 2.0.

The library is not tied to any particular architecture, the code should execute on x86, x64 and ia64.

Bugs/Feedback

If you encounter a scenario where code doesn't work as you expect, you're welcome to report a bug, initiate a pull request or send an email to t AT speot DOT is. The latter method is likely to elicit a response, but not guaranteed.

The above applies equally for feedback.