reactive/Ix.NET/Source/System.Interactive/System/Linq/Operators/DoWhile.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the Apache 2.0 License.
// See the LICENSE file in the project root for more information. 

using System.Collections.Generic;

namespace System.Linq
{
    public static partial class EnumerableEx
    {
        /// <summary>
        /// Generates an enumerable sequence by repeating a source sequence as long as the given loop postcondition holds.
        /// </summary>
        /// <typeparam name="TResult">Result sequence element type.</typeparam>
        /// <param name="source">Source sequence to repeat while the condition evaluates true.</param>
        /// <param name="condition">Loop condition.</param>
        /// <returns>Sequence generated by repeating the given sequence until the condition evaluates to false.</returns>
        public static IEnumerable<TResult> DoWhile<TResult>(this IEnumerable<TResult> source, Func<bool> condition)
        {
            if (source == null)
                throw new ArgumentNullException(nameof(source));
            if (condition == null)
                throw new ArgumentNullException(nameof(condition));

            return source.Concat(While(condition, source));
        }
    }
}