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Categories / C# / Collections Data Structure

 

Singleton IEnumerableT

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Lilium.Collections {     public static class EnumerableExtensions     {         public static T Single<T>(this IEnumerable<T> source, Func<Exception> empty, Func<Exception> many)         {             if (source == null) throw new ArgumentNullException("source");             if (empty == null) throw new ArgumentNullException("empty");             if (many == null) throw new ArgumentNullException("many");             using (var enumerator = source.GetEnumerator())                 if (enumerator.MoveNext())                 {                     var item = enumerator.Current;                     if (enumerator.MoveNext())                         throw many();                     else                         return item;                 }                 else throw empty();         }         public static IEnumerable<T> Singleton<T>(T value)         {             yield return value;         }         public static IEnumerable<T> Append<T>(this IEnumerable<T> source, T item)         {             if (source == null) throw new ArgumentNullException("source");             foreach (var current in source)                 yield return current;             yield return item;         }     } }