| using Cysharp.Threading.Tasks.Internal; | 
| using System; | 
| using System.Threading; | 
|   | 
| namespace Cysharp.Threading.Tasks.Linq | 
| { | 
|     public static partial class UniTaskAsyncEnumerable | 
|     { | 
|         public static UniTask<TSource> ElementAtAsync<TSource>(this IUniTaskAsyncEnumerable<TSource> source, int index, CancellationToken cancellationToken = default) | 
|         { | 
|             Error.ThrowArgumentNullException(source, nameof(source)); | 
|   | 
|             return ElementAt.ElementAtAsync(source, index, cancellationToken, false); | 
|         } | 
|   | 
|         public static UniTask<TSource> ElementAtOrDefaultAsync<TSource>(this IUniTaskAsyncEnumerable<TSource> source, int index, CancellationToken cancellationToken = default) | 
|         { | 
|             Error.ThrowArgumentNullException(source, nameof(source)); | 
|   | 
|             return ElementAt.ElementAtAsync(source, index, cancellationToken, true); | 
|         } | 
|     } | 
|   | 
|     internal static class ElementAt | 
|     { | 
|         public static async UniTask<TSource> ElementAtAsync<TSource>(IUniTaskAsyncEnumerable<TSource> source, int index, CancellationToken cancellationToken, bool defaultIfEmpty) | 
|         { | 
|             var e = source.GetAsyncEnumerator(cancellationToken); | 
|             try | 
|             { | 
|                 int i = 0; | 
|                 while (await e.MoveNextAsync()) | 
|                 { | 
|                     if (i++ == index) | 
|                     { | 
|                         return e.Current; | 
|                     } | 
|                 } | 
|   | 
|                 if (defaultIfEmpty) | 
|                 { | 
|                     return default; | 
|                 } | 
|                 else | 
|                 { | 
|                     throw Error.ArgumentOutOfRange(nameof(index)); | 
|                 } | 
|             } | 
|             finally | 
|             { | 
|                 if (e != null) | 
|                 { | 
|                     await e.DisposeAsync(); | 
|                 } | 
|             } | 
|         } | 
|     } | 
| } |