Domain helpers

Overview

Domain helpers are single purpose and reusable static classes to simplify usage of various functionality. Domain helpers are placed into Domain.Helpers namespace.

Queryable extensions

ApplyPagingFilter extension method

//usage of paging filter on queryable collection
var instances = dataQuery
    .OrderByDescending(x => x.ModifiedOn)
    .ApplyPagingFilter(query.PagingFilter)
    .ToList();

//implementation of paging filter for queryable collection
using System;
using System.Linq;
using ASOL.Core.Paging.Contracts.Filters;

namespace My.App.Domain.Helpers
{
    public static class QueryableExtensions
    {
        public static IQueryable<T> ApplyPagingFilter<T>(this IQueryable<T> query, PagingFilter pagingFilter)
        {
            if (pagingFilter == null) throw new ArgumentNullException(nameof(pagingFilter));

            return query
                .Skip(pagingFilter.Offset)
                .Take(pagingFilter.Limit);
        }
    }
}

Enumerable extensions

DistinctBy extension method

//usage of distinct with key-selector on enumerable collection
var qGroups = dataQuery
    .ToLookup(x => x.QualificationId);

//basic qualifications
var qList = new List<Qualification>();
foreach (var qGroup in qGroups)
{
    qList.AddRange(qGroup.Select(x => x.RelatedQualification));
}

//related qualifications
var qItems = qList.DistinctBy(x => x.Id);

//implementation of distinct with key-selector for enumerable collection
using System;
using System.Collections.Generic;
using System.Linq;

namespace My.App.Domain.Helpers
{
    public static class EnumerableExtensions
    {
        public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer = null)
        {
            var knownKeys = comparer == null ? new HashSet<TKey>() : new HashSet<TKey>(comparer);
            return source.Where(element => knownKeys.Add(keySelector(element)));
        }
    }
}