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October 18, 2022 14:33
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Enumerable With Metadata
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| public static class IndexedEnumerable | |
| { | |
| public static IndexedEnumerable<T> AsIndexedEnumerable<T>(this IEnumerable<T> source) | |
| { | |
| return Create(source); | |
| } | |
| public static IndexedEnumerable<T> Create<T>(IEnumerable<T> source) | |
| { | |
| return new IndexedEnumerable<T>(source); | |
| } | |
| } | |
| public class IndexedEnumerable<T> : IEnumerable<IndexedEnumerable<T>.EntryItem>, IEnumerable | |
| { | |
| private readonly IEnumerable<T> _enumerable; | |
| /// <summary> | |
| /// Default constructor. | |
| /// </summary> | |
| private IndexedEnumerable() | |
| { | |
| } | |
| /// <summary> | |
| /// Constructor that takes an IEnumerable<T> | |
| /// </summary> | |
| /// <param name="enumerable">The collection to enumerate.</param> | |
| public IndexedEnumerable(IEnumerable<T> enumerable) | |
| { | |
| if (enumerable == null) | |
| { | |
| throw new ArgumentNullException("enumerable"); | |
| } | |
| this._enumerable = enumerable; | |
| } | |
| /// <summary> | |
| /// Returns an enumeration of Entry objects. | |
| /// </summary> | |
| public IEnumerator<IndexedEnumerable<T>.EntryItem> GetEnumerator() | |
| { | |
| using IEnumerator<T> enumerator = _enumerable.GetEnumerator(); | |
| if (enumerator.MoveNext()) | |
| { | |
| int index = 0; | |
| bool first = true; | |
| bool isLast = false; | |
| while (!isLast) | |
| { | |
| T current = enumerator.Current; | |
| int currentIndex = index; | |
| isLast = !enumerator.MoveNext(); | |
| index = currentIndex + 1; | |
| yield return new EntryItem(first, isLast, current, currentIndex); | |
| first = false; | |
| } | |
| } | |
| } | |
| /// <summary>Non-generic form of GetEnumerator.</summary> | |
| IEnumerator IEnumerable.GetEnumerator() | |
| { | |
| return this.GetEnumerator(); | |
| } | |
| /// <summary> | |
| /// Represents each entry returned within a collection, | |
| /// containing the _value and whether it is the first and/or | |
| /// the last entry in the collection's. enumeration | |
| /// </summary> | |
| public class EntryItem | |
| { | |
| /// <summary> | |
| /// The index of the current item in the collection. | |
| /// </summary> | |
| public int Index | |
| { | |
| get; | |
| internal set; | |
| } | |
| /// <summary> | |
| /// Returns true if the current item has an even index | |
| /// </summary> | |
| public bool IsEven | |
| { | |
| get; | |
| internal set; | |
| } | |
| /// <summary> | |
| /// Returns true if it is the first item in the collection. | |
| /// </summary> | |
| public bool IsFirst | |
| { | |
| get; | |
| internal set; | |
| } | |
| /// <summary> | |
| /// Returns true if it is the last item in the collection. | |
| /// </summary> | |
| public bool IsLast | |
| { | |
| get; | |
| internal set; | |
| } | |
| /// <summary> | |
| /// Returns true if the current item has an odd index | |
| /// </summary> | |
| public bool IsOdd | |
| { | |
| get; | |
| internal set; | |
| } | |
| /// <summary> | |
| /// The Entry Value. | |
| /// </summary> | |
| public T Value | |
| { | |
| get; | |
| internal set; | |
| } | |
| internal EntryItem() | |
| { | |
| } | |
| internal EntryItem(bool isFirst, bool isLast, T value, int index) | |
| { | |
| this.IsFirst = isFirst; | |
| this.IsLast = isLast; | |
| this.Value = value; | |
| this.Index = index; | |
| this.IsEven = index % 2 == 0; | |
| this.IsOdd = !this.IsEven; | |
| } | |
| public static implicit operator T(IndexedEnumerable<T>.EntryItem item) | |
| { | |
| return item.Value; | |
| } | |
| } | |
| } |
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