CODEWITHSUNDEEP
c#stringsortingalphabetical
user818700
user818700

Reputation:

C# Sorting Strings only on first letter

I'm trying to sort a list of strings in alphabetical order in C#. My code looks like this:

public static List<Result> sort(List<Result> listToSort)
{
    int listSize = listToSort.Count;
    for (int i = 0; i < listSize; i++)
    {
       for (int j = 0; j < listSize; j++)
       {
           if (listToSort[i].SN[0] < listToSort[j].SN[0])
           { 
               Result tempValue = listToSort[j];
               listToSort[j] = listToSort[i];
               listToSort[i] = tempValue;
            }
        }
    }

    return listToSort;
}

But it's only sorting it based on the first letter of a string. In other words, if I have a list like this:

donald, abby, dave, bob, sam, pete

It will sort it like so:

abby, bob, donald, dave, pete, sam

One would expect 'dave' to come before 'donald'.. Any ideas?

Upvotes: 3

Views: 8390

Answers (6)

CodeNinja
CodeNinja

Reputation: 7

It was happened because of comparing character of the first string (listToSort[i].SN[0] => which produces the first character of your input). If you want to compare the string values, you should use string.Compare() method.

--SJ

Upvotes: 1

Henk Holterman
Henk Holterman

Reputation: 273264

Take a look at this part:

for (int i = 0; i < listSize; i++)
{
   for (int j = 0; j < listSize; j++)
   {
       if (listToSort[i].SN[0] < listToSort[j].SN[0])
       {

You are

  • only comparing on SN[0]. If SN is a string then that explains your main result.
  • always using the same compare, whether i < j or i > j

Best thing to do is to use a built-in sort. Linq's OrderBy(lambda) is the easiest but it creates a new list. For an in-place sort, use List<T>.Sort(Comparer).

If you do have to do it yourself, look up a good sorting algorithm (wikipedia).

Upvotes: 1

Daniel Pe&#241;alba
Daniel Pe&#241;alba

Reputation: 31857

You're only ever evaluating the first letter. Try using the traditional sorting method:

    public static void Sort(List<Result> listToSort)
    {
        listToSort.Sort(new ResultComparator());
    }

    public class ResultComparator : IComparer<Result>
    {
        public int Compare(Result x, Result y)
        {
            if (x == null && y == null) return 0;
            if (x == null) return 1;
            if (y == null) return 0;

            // compare based in SN
            return string.Compare(x.SN, y.SN);
        }
    }

Upvotes: 1

Paul Aldred-Bann
Paul Aldred-Bann

Reputation: 6020

How about using LINQ for this:

return listToSort.OrderBy(report => report.SN)

I'm assuming your Report class has a string property you want the list to be sorted by?

EDIT

Didn't notice that you'd already specified the SN property, have amended my answer.

Upvotes: 2

burning_LEGION
burning_LEGION

Reputation: 13450

public static List<Result> sort(List<Result> listToSort)
{        
    return listToSort.OrderBy(x=>x.SN[0]).ToList();
}

Upvotes: 1

Habib
Habib

Reputation: 223267

Currently you are only sorting by the first letter that is why you are seeing this result. You can use Enumerable.OrderBy - LINQ

List<Result> sortedList = listToSort.OrderBy(r=> r.SN).ToList();

Or for your current code you can modify your check to:

if (string.Compare(listToSort[i].SN,listToSort[j].SN) < 0)

Upvotes: 3

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