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copied!<p>There are several elements to the answer.</p> <p>The first part is being able to in-place sort a List using Sort() and a lambda comparison method. That's solved by using an extension method for IList and a helper "ComparisonDelegator" class. Combining those, it's possible to pass a lambda to List.Sort().</p> <p>The second part has been addressed in another post here (which I have upvoted) and the code from which I have shamelessly pasted into the AlphanumComparator class in this answer.</p> <p>(As a side note, I should point out that all the Linq examples posted elsewhere in this thread make a COPY of the list. This is fine for short lists, but if you have a long list it can cause performance problems. The solution presented here does NOT make a copy of the list.)</p> <p>Putting it all together, we get the following code, which outputs:</p> <pre><code>ID=2, Name=aaaa ID=3, Name=bbbb ID=1, Name=ccccc ID=5, Name=1 ID=7, Name=1a ID=6, Name=2 ID=4, Name=10 </code></pre> <p>And the full code sample (compilable as a console application):</p> <pre><code>using System; using System.Collections; using System.Collections.Generic; using System.Globalization; using System.Text; namespace Demo { public static class Program { public static void Main() { var list = new List<Essay> { new Essay {ID=1, Name="ccccc"}, new Essay {ID=2, Name="aaaa"}, new Essay {ID=3, Name="bbbb"}, new Essay {ID=4, Name="10"}, new Essay {ID=5, Name="1"}, new Essay {ID=6, Name="2"}, new Essay {ID=7, Name="1a"} }; var comp = new AlphanumComparator(); list.Sort((lhs, rhs) => comp.Compare(lhs.Name, rhs.Name)); foreach (var essay in list) { Console.WriteLine("ID={0}, Name={1}", essay.ID, essay.Name); } } } public class Essay { public int ID { get; set; } public string Name { get; set; } } /// <summary>Extensions for IList{T}</summary> public static class ListExt { /// <summary> Sorts an IList{T} in place. </summary> public static void Sort<T>(this IList<T> list, Comparison<T> comparison) { ArrayList.Adapter((IList)list).Sort(new ComparisonDelegator<T>(comparison)); } } /// <summary> /// Provides a mechanism for easily converting a Comparison&lt;&gt; delegate (or lambda) to an IComparer&lt;&gt;. /// This can be used for List.BinarySearch(), for example. /// </summary> /// <typeparam name="T">The type of items to be compared.</typeparam> public sealed class ComparisonDelegator<T>: IComparer<T>, IComparer { /// <summary>Create from a Comparison&lt;&gt; delegate.</summary> /// <param name="comparison">A Comparison&lt;&gt; delegate.</param> public ComparisonDelegator(Comparison<T> comparison) { this._comparison = comparison; } /// <summary>Implements the IComparer.Compare() method.</summary> public int Compare(T x, T y) { return _comparison(x, y); } /// <summary>Implements the IComparer.Compare() method.</summary> public int Compare(object x, object y) { return _comparison((T)x, (T)y); } /// <summary>Used to store the Comparison delegate.</summary> private readonly Comparison<T> _comparison; } /// <summary> /// Special class to sort strings "naturally", /// but to place non-numeric items *before* numeric items. /// </summary> public class AlphanumComparator : IComparer { private enum ChunkType {Alphanumeric, Numeric}; private bool InChunk(char ch, char otherCh) { ChunkType type = ChunkType.Alphanumeric; if (char.IsDigit(otherCh)) { type = ChunkType.Numeric; } if ((type == ChunkType.Alphanumeric && char.IsDigit(ch)) || (type == ChunkType.Numeric && !char.IsDigit(ch))) { return false; } return true; } public int Compare(object x, object y) { String s1 = x as string; String s2 = y as string; if (s1 == null || s2 == null) { return 0; } int thisMarker = 0, thisNumericChunk = 0; int thatMarker = 0, thatNumericChunk = 0; while ((thisMarker < s1.Length) || (thatMarker < s2.Length)) { if (thisMarker >= s1.Length) { return -1; } else if (thatMarker >= s2.Length) { return 1; } char thisCh = s1[thisMarker]; char thatCh = s2[thatMarker]; StringBuilder thisChunk = new StringBuilder(); StringBuilder thatChunk = new StringBuilder(); while ((thisMarker < s1.Length) && (thisChunk.Length==0 ||InChunk(thisCh, thisChunk[0]))) { thisChunk.Append(thisCh); thisMarker++; if (thisMarker < s1.Length) { thisCh = s1[thisMarker]; } } while ((thatMarker < s2.Length) && (thatChunk.Length==0 ||InChunk(thatCh, thatChunk[0]))) { thatChunk.Append(thatCh); thatMarker++; if (thatMarker < s2.Length) { thatCh = s2[thatMarker]; } } int result = 0; // If both chunks contain numeric characters, sort them numerically if (char.IsDigit(thisChunk[0]) && char.IsDigit(thatChunk[0])) { thisNumericChunk = Convert.ToInt32(thisChunk.ToString()); thatNumericChunk = Convert.ToInt32(thatChunk.ToString()); if (thisNumericChunk < thatNumericChunk) { result = -1; } if (thisNumericChunk > thatNumericChunk) { result = 1; } } else if (char.IsDigit(thisChunk[0]) && !char.IsDigit(thatChunk[0])) { return 1; // Ensure that non-numeric sorts before numeric. } else if (!char.IsDigit(thisChunk[0]) && char.IsDigit(thatChunk[0])) { return -1; // Ensure that non-numeric sorts before numeric. } else { result = thisChunk.ToString().CompareTo(thatChunk.ToString()); } if (result != 0) { return result; } } return 0; } } } </code></pre>

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