Created
April 1, 2012 16:58
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GroupAdjacentBy method for .NET in C#
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public static class LINQExtensions | |
{ | |
public static IEnumerable<IGrouping<TKey, TElement>> GroupAdjacentBy<TElement, TKey>(this IEnumerable<TElement> source, Func<TElement, TKey> keySelector, IEqualityComparer<TKey> comparer=null) | |
{ | |
comparer = comparer ?? EqualityComparer<TKey>.Default; | |
List<TElement> elements = null; | |
TKey key = default(TKey); | |
TKey lastKey = default(TKey); | |
foreach (var x in source) | |
{ | |
key = keySelector(x); | |
if (elements != null && elements.Any() && !comparer.Equals(lastKey, key)) | |
{ | |
yield return new Grouping<TKey, TElement>(lastKey, elements); | |
elements = null; | |
} | |
if (elements == null) | |
{ | |
elements = new List<TElement>(); | |
lastKey = key; | |
} | |
elements.Add(x); | |
} | |
if (elements != null && elements.Any()) | |
{ | |
yield return new Grouping<TKey, TElement>(key, elements); | |
} | |
} | |
public static IEnumerable<IGrouping<TElement, TElement>> GroupAdjacentBy<TElement>(this IEnumerable<TElement> source, IEqualityComparer<TElement> comparer=null) | |
{ | |
return source.GroupAdjacentBy(keySelector:x=>x,comparer:comparer); | |
} | |
// implement IGrouping | |
public class Grouping<TKey, TElement> : IGrouping<TKey, TElement> | |
{ | |
public TKey Key { get; private set; } | |
private List<TElement> Elements { get; set; } | |
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() | |
{ | |
return ((IEnumerable<TElement>)this).GetEnumerator(); | |
} | |
IEnumerator<TElement> IEnumerable<TElement>.GetEnumerator() | |
{ | |
return ((IEnumerable<TElement>)Elements).GetEnumerator(); | |
} | |
public Grouping(TKey key, List<TElement> elements) | |
{ | |
Key = key; | |
Elements = elements; | |
} | |
} | |
} |
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