361 lines
14 KiB
C#
361 lines
14 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using Umbraco.Core.Persistence.DatabaseModelDefinitions;
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namespace Umbraco.Core
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{
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///<summary>
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/// Extensions for enumerable sources
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///</summary>
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public static class EnumerableExtensions
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{
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internal static bool IsCollectionEmpty<T>(this IReadOnlyCollection<T> list) => list == null || list.Count == 0;
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internal static bool HasDuplicates<T>(this IEnumerable<T> items, bool includeNull)
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{
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var hs = new HashSet<T>();
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foreach (var item in items)
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{
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if ((item != null || includeNull) && !hs.Add(item))
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return true;
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}
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return false;
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}
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/// <summary>
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/// Wraps this object instance into an IEnumerable{T} consisting of a single item.
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/// </summary>
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/// <typeparam name="T"> Type of the object. </typeparam>
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/// <param name="item"> The instance that will be wrapped. </param>
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/// <returns> An IEnumerable{T} consisting of a single item. </returns>
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public static IEnumerable<T> Yield<T>(this T item)
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{
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// see EnumeratorBenchmarks - this is faster, and allocates less, than returning an array
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yield return item;
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}
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public static IEnumerable<IEnumerable<T>> InGroupsOf<T>(this IEnumerable<T> source, int groupSize)
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{
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if (source == null)
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throw new ArgumentNullException("source");
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if (groupSize <= 0)
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throw new ArgumentException("Must be greater than zero.", "groupSize");
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// following code derived from MoreLinq and does not allocate bazillions of tuples
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T[] temp = null;
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var count = 0;
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foreach (var item in source)
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{
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if (temp == null) temp = new T[groupSize];
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temp[count++] = item;
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if (count != groupSize) continue;
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yield return temp/*.Select(x => x)*/;
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temp = null;
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count = 0;
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}
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if (temp != null && count > 0)
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yield return temp.Take(count);
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}
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public static IEnumerable<TResult> SelectByGroups<TResult, TSource>(this IEnumerable<TSource> source, Func<IEnumerable<TSource>, IEnumerable<TResult>> selector, int groupSize)
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{
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// don't want to use a SelectMany(x => x) here - isn't this better?
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// ReSharper disable once LoopCanBeConvertedToQuery
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foreach (var resultGroup in source.InGroupsOf(groupSize).Select(selector))
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foreach (var result in resultGroup)
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yield return result;
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}
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/// <summary>The distinct by.</summary>
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/// <param name="source">The source.</param>
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/// <param name="keySelector">The key selector.</param>
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/// <typeparam name="TSource">Source type</typeparam>
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/// <typeparam name="TKey">Key type</typeparam>
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/// <returns>the unique list</returns>
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public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
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where TKey : IEquatable<TKey>
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{
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return source.Distinct(DelegateEqualityComparer<TSource>.CompareMember(keySelector));
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}
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/// <summary>
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/// Returns a sequence of length <paramref name="count"/> whose elements are the result of invoking <paramref name="factory"/>.
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="factory">The factory.</param>
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/// <param name="count">The count.</param>
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/// <returns></returns>
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public static IEnumerable<T> Range<T>(Func<int, T> factory, int count)
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{
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for (int i = 1; i <= count; i++)
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{
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yield return factory.Invoke(i - 1);
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}
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}
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/// <summary>The if not null.</summary>
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/// <param name="items">The items.</param>
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/// <param name="action">The action.</param>
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/// <typeparam name="TItem">The type</typeparam>
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public static void IfNotNull<TItem>(this IEnumerable<TItem> items, Action<TItem> action) where TItem : class
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{
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if (items != null)
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{
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foreach (TItem item in items)
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{
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item.IfNotNull(action);
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}
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}
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}
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/// <summary>
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/// Returns true if all items in the other collection exist in this collection
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/// </summary>
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/// <typeparam name="TSource"></typeparam>
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/// <param name="source"></param>
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/// <param name="other"></param>
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/// <returns></returns>
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public static bool ContainsAll<TSource>(this IEnumerable<TSource> source, IEnumerable<TSource> other)
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{
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if (source == null) throw new ArgumentNullException("source");
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if (other == null) throw new ArgumentNullException("other");
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return other.Except(source).Any() == false;
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}
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/// <summary>
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/// Returns true if the source contains any of the items in the other list
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/// </summary>
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/// <typeparam name="TSource"></typeparam>
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/// <param name="source"></param>
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/// <param name="other"></param>
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/// <returns></returns>
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public static bool ContainsAny<TSource>(this IEnumerable<TSource> source, IEnumerable<TSource> other)
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{
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return other.Any(source.Contains);
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}
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/// <summary>
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/// Removes all matching items from an <see cref="IList{T}"/>.
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="list">The list.</param>
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/// <param name="predicate">The predicate.</param>
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/// <remarks></remarks>
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public static void RemoveAll<T>(this IList<T> list, Func<T, bool> predicate)
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{
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for (var i = 0; i < list.Count; i++)
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{
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if (predicate(list[i]))
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{
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list.RemoveAt(i--);
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}
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}
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}
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/// <summary>
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/// Removes all matching items from an <see cref="ICollection{T}"/>.
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="list">The list.</param>
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/// <param name="predicate">The predicate.</param>
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/// <remarks></remarks>
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public static void RemoveAll<T>(this ICollection<T> list, Func<T, bool> predicate)
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{
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var matches = list.Where(predicate).ToArray();
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foreach (var match in matches)
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{
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list.Remove(match);
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}
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}
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public static IEnumerable<TSource> SelectRecursive<TSource>(
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this IEnumerable<TSource> source,
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Func<TSource, IEnumerable<TSource>> recursiveSelector, int maxRecusionDepth = 100)
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{
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var stack = new Stack<IEnumerator<TSource>>();
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stack.Push(source.GetEnumerator());
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try
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{
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while (stack.Count > 0)
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{
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if (stack.Count > maxRecusionDepth)
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throw new InvalidOperationException("Maximum recursion depth reached of " + maxRecusionDepth);
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if (stack.Peek().MoveNext())
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{
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var current = stack.Peek().Current;
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yield return current;
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stack.Push(recursiveSelector(current).GetEnumerator());
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}
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else
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{
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stack.Pop().Dispose();
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}
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}
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}
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finally
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{
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while (stack.Count > 0)
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{
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stack.Pop().Dispose();
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}
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}
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}
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/// <summary>
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/// Filters a sequence of values to ignore those which are null.
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="coll">The coll.</param>
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/// <returns></returns>
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/// <remarks></remarks>
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public static IEnumerable<T> WhereNotNull<T>(this IEnumerable<T> coll) where T : class
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{
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return coll.Where(x => x != null);
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}
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public static IEnumerable<TBase> ForAllThatAre<TBase, TActual>(this IEnumerable<TBase> sequence, Action<TActual> projection)
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where TActual : class
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{
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return sequence.Select(
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x =>
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{
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if (x is TActual)
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{
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var casted = x as TActual;
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projection.Invoke(casted);
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}
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return x;
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});
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}
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/// <summary>
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/// Finds the index of the first item matching an expression in an enumerable.
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/// </summary>
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/// <typeparam name="T">The type of the enumerated objects.</typeparam>
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/// <param name="items">The enumerable to search.</param>
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/// <param name="predicate">The expression to test the items against.</param>
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/// <returns>The index of the first matching item, or -1.</returns>
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public static int FindIndex<T>(this IEnumerable<T> items, Func<T, bool> predicate)
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{
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return FindIndex(items, 0, predicate);
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}
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/// <summary>
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/// Finds the index of the first item matching an expression in an enumerable.
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/// </summary>
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/// <typeparam name="T">The type of the enumerated objects.</typeparam>
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/// <param name="items">The enumerable to search.</param>
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/// <param name="startIndex">The index to start at.</param>
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/// <param name="predicate">The expression to test the items against.</param>
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/// <returns>The index of the first matching item, or -1.</returns>
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public static int FindIndex<T>(this IEnumerable<T> items, int startIndex, Func<T, bool> predicate)
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{
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if (items == null) throw new ArgumentNullException("items");
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if (predicate == null) throw new ArgumentNullException("predicate");
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if (startIndex < 0) throw new ArgumentOutOfRangeException("startIndex");
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var index = startIndex;
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if (index > 0)
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items = items.Skip(index);
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foreach (var item in items)
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{
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if (predicate(item)) return index;
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index++;
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}
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return -1;
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}
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///<summary>Finds the index of the first occurrence of an item in an enumerable.</summary>
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///<param name="items">The enumerable to search.</param>
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///<param name="item">The item to find.</param>
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///<returns>The index of the first matching item, or -1 if the item was not found.</returns>
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public static int IndexOf<T>(this IEnumerable<T> items, T item)
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{
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return items.FindIndex(i => EqualityComparer<T>.Default.Equals(item, i));
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}
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/// <summary>
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/// Determines if 2 lists have equal elements within them regardless of how they are sorted
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="source"></param>
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/// <param name="other"></param>
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/// <returns></returns>
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/// <remarks>
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/// The logic for this is taken from:
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/// http://stackoverflow.com/questions/4576723/test-whether-two-ienumerablet-have-the-same-values-with-the-same-frequencies
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///
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/// There's a few answers, this one seems the best for it's simplicity and based on the comment of Eamon
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/// </remarks>
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public static bool UnsortedSequenceEqual<T>(this IEnumerable<T> source, IEnumerable<T> other)
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{
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if (source == null && other == null) return true;
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if (source == null || other == null) return false;
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var list1Groups = source.ToLookup(i => i);
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var list2Groups = other.ToLookup(i => i);
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return list1Groups.Count == list2Groups.Count
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&& list1Groups.All(g => g.Count() == list2Groups[g.Key].Count());
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}
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/// <summary>
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/// Transforms an enumerable.
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="source"></param>
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/// <param name="transform"></param>
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/// <returns></returns>
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public static IEnumerable<TTarget> Transform<TSource, TTarget>(this IEnumerable<TSource> source, Func<IEnumerable<TSource>, IEnumerable<TTarget>> transform)
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{
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return transform(source);
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}
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/// <summary>
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/// Gets a null IEnumerable as an empty IEnumerable.
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="items"></param>
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/// <returns></returns>
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public static IEnumerable<T> EmptyNull<T>(this IEnumerable<T> items)
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{
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return items ?? Enumerable.Empty<T>();
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}
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// the .OfType<T>() filter is nice when there's only one type
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// this is to support filtering with multiple types
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public static IEnumerable<T> OfTypes<T>(this IEnumerable<T> contents, params Type[] types)
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{
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return contents.Where(x => types.Contains(x.GetType()));
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}
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public static IEnumerable<T> SkipLast<T>(this IEnumerable<T> source)
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{
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using (var e = source.GetEnumerator())
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{
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if (e.MoveNext() == false) yield break;
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for (var value = e.Current; e.MoveNext(); value = e.Current)
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yield return value;
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}
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}
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public static IOrderedEnumerable<TSource> OrderBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Direction sortOrder)
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{
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return sortOrder == Direction.Ascending ? source.OrderBy(keySelector) : source.OrderByDescending(keySelector);
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}
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}
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}
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