I am using this linq query to sort a string column but the results I am getting does not seems to be in right order?
Query:
userList = users.OrderBy(u => u.FirstName)
.Skip(offset)
.Take(rowcount)
.ToList<User>();
Result:
rama &
11Rama
15rama
1Rama
2Rama
490110rama
IU-Rama
Rama
it should be something like?
1Rama
2Rama
11Rama
15rama
490110rama
IU-Rama
rama &
Rama
You are getting your result sorted by the code points of the characters and that is by far the most common implementation for sorting strings. What you are expecting is called natural sort order, see for example this article, but you will have to do it on your own because .NET does not provide this out of the box.
By adding this code you will be able to sort as you need it to be done. But this sorting will be done on client side and all records must be fetch as list.
userList = users.ToList<User>()
.OrderBy(u => u.FirstName,new NumericComparer())
.Skip(offset)
.Take(rowcount)
.ToList<User>();
public class NumericComparer : IComparer<string>
{
public int Compare(string x, string y)
{
return StringLogicalComparer.Compare(x, y);
}
}
public class StringLogicalComparer
{
public static int Compare(string s1, string s2)
{
//get rid of special cases
if ((s1 == null) && (s2 == null)) return 0;
if (s1 == null) return -1;
if (s2 == null) return 1;
if ((s1.Equals(string.Empty) && (s2.Equals(string.Empty)))) return 0;
if (s1.Equals(string.Empty)) return -1;
if (s2.Equals(string.Empty)) return -1;
//WE style, special case
bool sp1 = Char.IsLetterOrDigit(s1, 0);
bool sp2 = Char.IsLetterOrDigit(s2, 0);
if (sp1 && !sp2) return 1;
if (!sp1 && sp2) return -1;
int i1 = 0, i2 = 0; //current index
while (true)
{
bool c1 = Char.IsDigit(s1, i1);
bool c2 = Char.IsDigit(s2, i2);
int r; // temp result
if (!c1 && !c2)
{
bool letter1 = Char.IsLetter(s1, i1);
bool letter2 = Char.IsLetter(s2, i2);
if ((letter1 && letter2) || (!letter1 && !letter2))
{
r = letter1 ? Char.ToLower(s1[i1]).CompareTo(Char.ToLower(s2[i2])) : s1[i1].CompareTo(s2[i2]);
if (r != 0) return r;
}
else if (!letter1) return -1;
else return 1;
}
else if (c1 && c2)
{
r = CompareNum(s1, ref i1, s2, ref i2);
if (r != 0) return r;
}
else if (c1)
{
return -1;
}
else
{
return 1;
}
i1++;
i2++;
if ((i1 >= s1.Length) && (i2 >= s2.Length))
{
return 0;
}
if (i1 >= s1.Length)
{
return -1;
}
if (i2 >= s2.Length)
{
return -1;
}
}
}
private static int CompareNum(string s1, ref int i1, string s2, ref int i2)
{
int nzStart1 = i1, nzStart2 = i2; // nz = non zero
int end1 = i1, end2 = i2;
ScanNumEnd(s1, i1, ref end1, ref nzStart1);
ScanNumEnd(s2, i2, ref end2, ref nzStart2);
int start1 = i1; i1 = end1 - 1;
int start2 = i2; i2 = end2 - 1;
int nzLength1 = end1 - nzStart1;
int nzLength2 = end2 - nzStart2;
if (nzLength1 < nzLength2) return -1;
if (nzLength1 > nzLength2) return 1;
for (int j1 = nzStart1, j2 = nzStart2; j1 <= i1; j1++, j2++)
{
int r = s1[j1].CompareTo(s2[j2]);
if (r != 0) return r;
}
// the nz parts are equal
int length1 = end1 - start1;
int length2 = end2 - start2;
if (length1 == length2) return 0;
if (length1 > length2) return -1;
return 1;
}
private static void ScanNumEnd(string s, int start, ref int end, ref int nzStart)
{
nzStart = start;
end = start;
bool countZeros = true;
while (Char.IsDigit(s, end))
{
if (countZeros && s[end].Equals('0'))
{
nzStart++;
}
else countZeros = false;
end++;
if (end >= s.Length) break;
}
}
}
Creating a custom IComparer would work for you.
Check this implementation: http://zootfroot.blogspot.com/2009/09/natural-sort-compare-with-linq-orderby.html
You code would then call myLinqQuery.OrderBy(item => item.sortProperty, new MyComparer<string>())
In his example, the sort order return:
image1.jpg
image4.jpg
image30.jpg
image200.jpg
