SpecificationExtensions

This repository contains two projects

- t0pez.SpecificationExtensions.Core

- t0pez.SpecificationExtensions.Generators

These two packages adds a few extensions for Ardalis.Specification package. Using these packages gives you an opportunity make you specifications more reusable

Package SpecificationExtensions.Core

Provides few base specifications and extesions for them

Class BaseSpec<TModel>

Adds method for paging

public BaseSpec<TModel> EnablePaging(int skip, int take);

Wich one gives you opportunity to easily use your own values

var spec = new BaseSpec<Entity>().EnablePaging(10, 20);

Or you could write your own extension method using this one to use your own pagination filters

Example:

public static BaseSpec<T> EnablePaginationFilter<T>(this BaseSpec<T> spec, YourPaginationFilter filter)
{
    return spec.EnablePaging(filter.Skip, filter.Take);
}

---

Also it provides ExceptBy method with two overloads, which accepts whole models or only values you need to except.

public BaseSpec<TModel> ExceptBy<TKey>(IEnumerable<TModel> models, Expression<Func<TModel, TKey>> selector);
public BaseSpec<TModel> ExceptBy<TKey>(IEnumerable<TKey> values, Expression<Func<TModel, TKey>> selector);

Example:

var entitiesToExcept = ...;
var spec = new SomeEntitySpec().ExceptBy(entitiesToExcept, entity => entity.Name);

---

Class SelectSpec<TModel, TResult>

Contains constructor which applied in extension method

Specification<TModel, TResult> Select<TModel, TResult>(this Specification<TModel> spec, Expression<Func<TModel, TResult>> selector)

Which one gives you an opportunity to make Select from already existing specs

var spec = new SomeEntitySpec().Select(entity => entity.Name);

---

Also this package contains an SafeDeleteSpecAttribute. For use it you need next package

Package SpecificationExtensions.Generators

Provides source code generation of SafeDeleteSpec class

If you have a concept of safe deletion in your project (marking entity as deleted with boolean flag), you might want to have search specification that sets default predicate for it

Class SafeDeleteSpec needs an base class or an interface wich you use to provide your boolean flag and name of this field. It automatically inherits BaseSpec class

All you need to have this class is create an empty partial class with SafeDeleteSpecAttribute

public interface ISafeDelete
{
    bool IsDeleted { get; set; }
}

[SafeDeleteSpec(typeof(ISafeDelete), nameof(ISafeDelete.IsDeleted))]
public partial class SafeDeleteSpec<TModel>
{
}

Pass to constuctor typeof() expression of your class/interface and nameof expression of required field

Warning! nameof() expression is required. Don't try to write string literal there!

This will generate a class for you. Which by default searches only for entities with deletion status false

But if you need to choose other variant of predicate you can call one of the method that class has

public SafeDeleteSpec<TModel> LoadAll();
public SafeDeleteSpec<TModel> LoadOnlyDeleted();
public SafeDeleteSpec<TModel> LoadOnlyNotDeleted();

And you can use it right in point of use

Also you can combine all of this extensions

public class SafeDeleteEntityByNameSpec : SafeDeleteSpec<SafeDeleteEntity>
{
    public SafeDeleteEntityByNameSpec(string containingName)
    {
        Query
          .Where(entity => entity.Name.Contains(containingName));
    }
}

var entitiesToExcept = ...;
var spec = new SafeDeleteEntityByNameSpec(predicateName)
                   .LoadAll()
                   .ExceptBy(entitiesToExcept, entity => entity.Name)
                   .Select(entity => entity.Name);