I have a generic
List<MyClass>
where MyClass has a property InvoiceNumber which contains values such as:
200906/1
200906/2
..
200906/10
200906/11
200906/12
My list is bound to a
BindingList<T>
which supports sorting with linq:
protected override void ApplySortCore(
PropertyDescriptor property, ListSortDirection direction)
{
_sortProperty = property;
_sortDirection = direction;
var items = this.Items;
switch (direction)
{
case ListSortDirection.Ascending:
items = items.OrderByDescending(x => property.GetValue(x)).ToList();
break;
case ListSortDirection.Descending:
items = items.OrderByDescending(x => property.GetValue(x)).ToList();
break;
}
this.Items = items;
}
However the default comparer sorts (as supposed) like this:
200906/1
200906/10
200906/11
200906/12
200906/2
which is nasty in this case.
Now I want to use my own IComparer<T> with this. It looks like this:
public class MyComparer : IComparer<Object>
{
public int Compare(Object stringA, Object stringB)
{
String[] valueA = stringA.ToString().Split('/');
String[] valueB = stringB.ToString().Split('/');
if(valueA .Length != 2 || valueB .Length != 2)
return String.Compare(stringA.ToString(), stringB.ToString());
if (valueA[0] == valueB[0])
{
return String.Compare(valueA[1], valueB[1]);
}
else
{
return String.Compare(valueA[0], valueB[0]);
}
}
}
and changed the ApplySortCore code to use this IComparer:
case ListSortDirection.Ascending:
MyComparer comparer = new MyComparer();
items = items.OrderByDescending(
x => property.GetValue(x), comparer).ToList();
break;
When I debug my code, I see that MyComparer.Compare(object, object) is called multiple times and returns the right values (-1, 0, 1) for a compare method.
But my list is still sorted the "wrong" way. Am I missing something? I have no clue.
Jon Skeet
Your comparer looks wrong to me. You're still just sorting in the default text ordering. Surely you want to be parsing the two numbers and sorting based on that:
public int Compare(Object stringA, Object stringB)
{
string[] valueA = stringA.ToString().Split('/');
string[] valueB = stringB.ToString().Split('/');
if (valueA.Length != 2 || valueB.Length != 2)
{
stringA.ToString().CompareTo(stringB.ToString());
}
// Note: do error checking and consider i18n issues too :)
if (valueA[0] == valueB[0])
{
return int.Parse(valueA[1]).CompareTo(int.Parse(valueB[1]));
}
else
{
return int.Parse(valueA[0]).CompareTo(int.Parse(valueB[0]));
}
}
(Note that this doesn't sit well with your question stating that you've debugged through and verified that Compare is returning the right value - but I'm afraid I suspect human error on that front.)
Additionally, Sven's right - changing the value of items doesn't change your bound list at all. You should add:
this.Items = items;
at the bottom of your method.
James McCormack
I encountered the issue of general natural sorting and blogged the solution here:
Natural Sort Compare with Linq OrderBy()
public class NaturalSortComparer<T> : IComparer<string>, IDisposable
{
private bool isAscending;
public NaturalSortComparer(bool inAscendingOrder = true)
{
this.isAscending = inAscendingOrder;
}
#region IComparer<string> Members
public int Compare(string x, string y)
{
throw new NotImplementedException();
}
#endregion
#region IComparer<string> Members
int IComparer<string>.Compare(string x, string y)
{
if (x == y)
return 0;
string[] x1, y1;
if (!table.TryGetValue(x, out x1))
{
x1 = Regex.Split(x.Replace(" ", ""), "([0-9]+)");
table.Add(x, x1);
}
if (!table.TryGetValue(y, out y1))
{
y1 = Regex.Split(y.Replace(" ", ""), "([0-9]+)");
table.Add(y, y1);
}
int returnVal;
for (int i = 0; i < x1.Length && i < y1.Length; i++)
{
if (x1[i] != y1[i])
{
returnVal = PartCompare(x1[i], y1[i]);
return isAscending ? returnVal : -returnVal;
}
}
if (y1.Length > x1.Length)
{
returnVal = 1;
}
else if (x1.Length > y1.Length)
{
returnVal = -1;
}
else
{
returnVal = 0;
}
return isAscending ? returnVal : -returnVal;
}
private static int PartCompare(string left, string right)
{
int x, y;
if (!int.TryParse(left, out x))
return left.CompareTo(right);
if (!int.TryParse(right, out y))
return left.CompareTo(right);
return x.CompareTo(y);
}
#endregion
private Dictionary<string, string[]> table = new Dictionary<string, string[]>();
public void Dispose()
{
table.Clear();
table = null;
}
}
Michał Kuliński
You can use The Alphanum Algorithm:
(...)
items.OrderBy(x => property.GetValue(x), new AlphanumComparator())
(...)
/*
* The Alphanum Algorithm is an improved sorting algorithm for strings
* containing numbers. Instead of sorting numbers in ASCII order like
* a standard sort, this algorithm sorts numbers in numeric order.
*
* The Alphanum Algorithm is discussed at http://www.DaveKoelle.com
*
* Based on the Java implementation of Dave Koelle's Alphanum algorithm.
* Contributed by Jonathan Ruckwood <jonathan.ruckwood@gmail.com>
*
* Adapted by Dominik Hurnaus <dominik.hurnaus@gmail.com> to
* - correctly sort words where one word starts with another word
* - have slightly better performance
*
* Released under the MIT License - https://opensource.org/licenses/MIT
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
* USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
using System;
using System.Collections;
using System.Text;
/*
* Please compare against the latest Java version at http://www.DaveKoelle.com
* to see the most recent modifications
*/
namespace AlphanumComparator
{
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
{
result = thisChunk.ToString().CompareTo(thatChunk.ToString());
}
if (result != 0)
{
return result;
}
}
return 0;
}
}
}
Can't we do like this:
public class MyComparer : IComparer<string>
{
public int Compare(string stringA, string stringB)
{
string small = stringA;
string big = stringB;
if (stringA.Length > stringB.Length)
{
small = stringB;
big = stringA;
}
else if (stringA.Length < stringB.Length)
{
small = stringA;
big = stringB;
}
for (int j = 0; j < small.Length; j++)
{
if (Convert.ToInt32(small[j]) > Convert.ToInt32(big[j])) return -1;
if (Convert.ToInt32(small[j]) < Convert.ToInt32(big[j])) return 1;
}
//big is indeed bigger
if (big.Length > small.Length) return 1;
//finally they are smae
return 0;
}
}
Usage:
string[] inputStrings = {"_abc*&","#almnp","abc" };
//string[] inputStrings = { "#", "_", "_a", "@", "_" };
MyComparer computer = new MyComparer();
var kola = inputStrings.OrderBy(x => x, new MyComparer()).ToArray();
This is same as :
Array.Sort(inputStrings, StringComparer.Ordinal);
The sorted list is only bound to the local variable items, not to the Items property of your binding list, hence it remains unsorted.
[Edit] Basically, you're simply throwing away the result of your sorting efforts ;-)
来源：https://stackoverflow.com/questions/985657/use-own-icomparert-with-linq-orderby