Why is string array getting sorted improperly? [duplicate]

Question

I'm fairly new in C# and just encountered a weird behavior.

This is a piece of script that should sort array of strings alphabetically (A-Z)

This is the array:

IFF-7/12
IFA-7/11
IFF-7/8
IFF-7/2
IFF-7/11
IFF-7/1
IF-7/1
IFF-7/6
IFF-7/9
IFF-7/13
IFF-7/14
IF-7/2

So I suppose the outcome should be:

IF-7/1
IF-7/2
IFA-7/11
IFF-7/1
IFF-7/2
IFF-7/6
IFF-7/8
IFF-7/9
IFF-7/11
IFF-7/12
IFF-7/13
IFF-7/14

Program script:

 for (int i = 0; i < faculty.GroupCount; i++)
        {
            for (int j = i + 1; j < faculty.GroupCount; j++)
            {
                if (faculty.Groups[j].Name.CompareTo(faculty.Groups[i].Name) < 0)
                {
                    temp = faculty.Groups[i];
                    faculty.Groups[i] = faculty.Groups[j];
                    faculty.Groups[j] = temp;
                }
            }
        }

But the actual outcome is

IF-7/1
IF-7/2
IFA-7/11
IFF-7/1
IFF-7/11
IFF-7/12
IFF-7/13
IFF-7/14
IFF-7/2
IFF-7/6
IFF-7/8
IFF-7/9

I see what it's doing but I have no idea why. Also I can't use any of the libraries or methods like .sort .

Thanks for any help.

You should implement this using IComparer<T> instead : msdn.microsoft.com/en-us/library/8ehhxeaf(v=vs.110).aspx — aybe
– aybe, Commented Oct 9, 2017 at 13:23
Because numbers sorted as string go 1,10,11,12,2,3,4,5,6,7,8,9 .. because all the ones come before 2.. — BugFinder
– BugFinder, Commented Oct 9, 2017 at 13:25
What you want is called a natural sort order, as opposed to alphabetical sort order (default implementation of CompareTo). There are multiple older question on that natural sorting: 1, 2, 3. You might want to check them out and apply the code there to your particular problem. — default locale
– default locale, Commented Oct 9, 2017 at 13:29
Your supposed outcome is incorrect, because of the assumption that dash - sorts after letters, while in fact it sorts before letters, and even before digits (its hex code is 0x45, while the code of zero '0' is 0x48). — Sergey Kalinichenko
– Sergey Kalinichenko, Commented Oct 9, 2017 at 13:29

Jon Hanna · Accepted Answer · 2017-10-09 13:26:32Z

3

1 comes before 2 in the order the same way that A comes before B, so 11 comes before 2.

You seem to want what is often called a "natural sort" which is like an alphabetical sort except that where two strings with the same beginning differ in numbers then the numerical value of the number as a whole (all of the run of digits) are compared. This isn't a collation provided by the .NET framework directly, but answers like this explain how to create an IComparer<string> that does a natural sort.

answered Oct 9, 2017 at 13:26

Jon Hanna

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