readme-nuget.md

A .NET library for building query specifications.

• Pozitron.QuerySpecification A base package containing the core functionality, in-memory evaluators, and validators.
• Pozitron.QuerySpecification.EntityFrameworkCore An EntityFramework Core plugin to the base package. It contains EF specific evaluators.

Usage

Create your specification classes by inheriting from the Specification<T> class, and use the builder Query to build your queries in the constructor.

public class CustomerSpec : Specification<Customer>
{
  public CustomerSpec(int age, string nameTerm)
  {
    Query
      .Where(x => x.Age > age)
      .Like(x => x.Name, $"%{nameTerm}%")
      .Include(x => x.Addresses)
          .ThenInclude(x => x.Contact)
      .OrderBy(x => x.Id)
          .ThenBy(x => x.Name)
      .Skip(10)
      .Take(10)
      .AsSplitQuery();
  }
}

Apply the specification to DbSet<T> or to any IQueryable<T> source.

var spec = new CustomerSpec(30, "John");

List<Customer> result = await _context
    .Customers
    .WithSpecification(spec)
    .ToListAsync();

Projections

The specification can be used to project the result into a different type. Inherit from Specification<T, TResult> class, where TResult is the type you want to project into. This offers strongly typed experience in the builder and during the evaluation.

public class CustomerDtoSpec : Specification<Customer, CustomerDto>
{
  public CustomerDtoSpec(int age, string nameTerm)
  {
    Query
      .Where(x => x.Age > age)
      .Like(x => x.Name, $"%{nameTerm}%")
      .OrderBy(x => x.Name)
      .Select(x => new CustomerDto(x.Id, x.Name));
  }
}

Apply the specification to DbSet<T> or any IQueryable<T> source.

var spec = new CustomerSpec(30, "John");

List<CustomerDto> result = await _context
    .Customers
    .WithSpecification(spec)
    .ToListAsync();

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