Validation result

Error

Parameters

Info

Checks if length of candidate is equal to specific value.

Candidate must implement IEnumerable interface.
Note that, string is also a collection, and can be used with this Specification.

Usage

var spec = Specification.Length<int[]>(3);

spec.IsSatisfiedBy(new int[] {100, 200, 0});  // true
spec.IsSatisfiedBy(new int[] {100, 200});    // false
spec.IsSatisfiedBy(new int[0]);  // false
spec.IsSatisfiedBy(null);   // false

As property

var customerSpec = Specification.Length<Customer, string>(c => c.Comments, 3);

customerSpec.IsSatisfiedBy(new Customer { Comments = "VIP" });  // true
customerSpec.IsSatisfiedBy(new Customer { Comments = "0" });    // false
customerSpec.IsSatisfiedBy(new Customer { Comments = "" });  // false
customerSpec.IsSatisfiedBy(new Customer { Comments = null });   // false

Not Length

var spec = Specification.NotLength<int[]>(3);

spec.IsSatisfiedBy(new int[] {100, 200, 0});  // false
spec.IsSatisfiedBy(new int[] {100, 200});    // true
spec.IsSatisfiedBy(new int[0]);  // true
spec.IsSatisfiedBy(null);   // true

As property

var customerSpec = Specification.NotLength<Customer, string>(c => c.Comments, 3);

customerSpec.IsSatisfiedBy(new Customer { Comments = "VIP" });  // false
customerSpec.IsSatisfiedBy(new Customer { Comments = "0" });    // true
customerSpec.IsSatisfiedBy(new Customer { Comments = "" });  // true
customerSpec.IsSatisfiedBy(new Customer { Comments = null });   // true

EF 6 support

In Linq to entities compare collections with null generates NotSupportedException.
To prevent this, use linqToEntities constructor flag or global Specification.LinqToEntities flag.

using (var context = new EfDbContext())
{
    var anyItemsSpec = Specification.Length<Customer, ICollection<Item>>(c => c.Items, 5);
    // var customers = context.Customers.Where(anyItemsSpec.GetExpression()).ToList();   // Exception!

    Specification.LinqToEntities = true;
    var anyItemsSpecFixed = Specification.Length<Customer, ICollection<Item>>(c => c.Items, 5);
    var customers = context.Customers.Where(anyItemsSpecFixed.GetExpression()).ToList();   // Works!
}