Possible issue with IComparer and SortedDictionary

Question

I am trying to create a SortedDictionary where its key is a string that represents a File/Folder path. I am trying to sort that dictionary based on path depths. My criteria just checks for the number of slashes in each path and puts the path with the most slashes at the beginning of the dictionary.

My problem is that for some weird issue that I cant detect, the dictionary can have multiple keys that are exactly the same. The problem after hours of debugging seem to be that "sometimes" my IComparer implementation does not loop over all entries in the dictionary when calling ContainsKey method or when adding a new value to the dictionary. I don't get an exception or anything.

This is my code.. (Its a bit long as):

 namespace ConsoleApplication1
{

    class DepthComparer : IComparer<string>
    {
        public int Compare(string X, string Y)
        {
            //Sort From deepest to shallowest 
            //C:\Users\NAME\Desktop\Folder\ should precede C:\Users\NAME\Desktop\
            //Paths with same root level are ignored

            int nXSlashes = SlashCounter(X);
            int nYSlashes = SlashCounter(Y);

            if (string.Compare(X, Y, true) == 0) //same path
            {
                return 0;
            }

            //Put Deepest Path at the beginning
            return (nXSlashes > nYSlashes ? -1 : 1);

        }

        public int SlashCounter(string stPath)
        {
            int nSlashes = 0;
            for (int i = 0; i < stPath.Length - 1; ++i)
            {
                if (stPath[i] == ('/') || stPath[i] == ('\\'))
                    nSlashes++;
            }
            return nSlashes;
        }
    }

    public class ScanOptions
    {
        public enum ExcludeRule
        {
            Invalid = 0x00,
            File = 0x01,
            Folder = 0x02,
            FileFolder = File | Folder,
        }

        private SortedDictionary<string, ExcludeRule> _dExcludedPaths;

        public ScanOptions()
        {
            _dExcludedPaths = null;            
        }

        //Creates a new Excluded Paths List (Automatically clears the current list if its already initialized)
        public void CreateExcludedPathsList()
        {
            if (_dExcludedPaths == null)
                _dExcludedPaths = new SortedDictionary<string, ExcludeRule>(new DepthComparer());
            else
                ClearExcludedPathsList();
        }

        public void ClearExcludedPathsList()
        {
            _dExcludedPaths.Clear();
        }

        public bool IsExcludedPathsListInitialized()
        {
            return _dExcludedPaths != null ? true : false;
        }

        public void AddExcludePath(string stPath, ExcludeRule Rule)
        {
            if (!IsExcludedPathsListInitialized())
                return;

            if (string.IsNullOrEmpty(stPath) || Rule == ExcludeRule.Invalid)
                return;

            string stTmp = stPath.ToLower();
            try
            {
                if (stTmp.EndsWith("\\"))
                {
                    stTmp = stTmp.Remove(stTmp.Length - 1);
                }

                if (_dExcludedPaths.ContainsKey(stTmp))
                {
                    ExcludeRule OldRule = ExcludeRule.Invalid;
                    if (_dExcludedPaths.TryGetValue(stTmp, out OldRule))
                    {
                        if ((OldRule & Rule) == 0)
                            _dExcludedPaths[stTmp] |= Rule; //Same path new rule, append rule to existing one
                    }
                    return;
                }
                else
                {
                    //brand new entry
                    _dExcludedPaths[stTmp] = Rule;
                }
            }
            catch
            {

            }
        }

        public void AddExcludePaths(List<string> ExcludePaths, ExcludeRule Rule)
        {
            if (!IsExcludedPathsListInitialized())
                return;

            foreach (string stPath in ExcludePaths)
                AddExcludePath(stPath, Rule);
        }

        public void AddExcludePaths(SortedDictionary<string, ExcludeRule> ExcludePaths)
        {
            if (!IsExcludedPathsListInitialized())
                return;

            foreach (KeyValuePair<string, ExcludeRule> PathRule in ExcludePaths)
                AddExcludePath(PathRule.Key, PathRule.Value);
        }


        public void ShowInConsole()
        {
           foreach (KeyValuePair<string, ScanOptions.ExcludeRule> Rule in _dExcludedPaths)
            {
                Console.WriteLine(Rule.Key + "\t" + Rule.Value);
            }
        }

    }

    class Program
    {
        static void Main(string[] args)
        {

            string desktopPath = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory);

            //Fill a new string list with some paths
            List<string> ExcludedPaths = new List<string>();
            string ExPath = desktopPath + "\\12345678\\";
            ExcludedPaths.Add(ExPath);
            ExPath = desktopPath + "\\abcdefg\\";
            ExcludedPaths.Add(ExPath);
            ExPath = desktopPath + "\\ABCDEFG\\";
            ExcludedPaths.Add(ExPath);
            ExPath = desktopPath + "\\1A2B3C 4D5E6F\\123456\\4567896\\";
            ExcludedPaths.Add(ExPath);
            ExPath = desktopPath + "\\CDEVQWER ASD\\456786\\";
            ExcludedPaths.Add(ExPath);

            //Create the exclude list object
            ScanOptions scanOpt = new ScanOptions();
            scanOpt.CreateExcludedPathsList();

            //First manually add one of the paths from the list above
            scanOpt.AddExcludePath(desktopPath + "\\12345678\\", ScanOptions.ExcludeRule.Folder);

            //Now add the whole list of paths to the exclude list in scan options
            scanOpt.AddExcludePaths(ExcludedPaths, ScanOptions.ExcludeRule.Folder);

            //Now add the first entry a couple more times with different value each time
            scanOpt.AddExcludePath(desktopPath + "\\12345678\\", ScanOptions.ExcludeRule.File);

            scanOpt.AddExcludePath(desktopPath + "\\12345678\\", ScanOptions.ExcludeRule.Folder);


            //Dump the list to console
            //We now have two keys in the dictionary that equal desktopPath + "\\12345678\\"
            scanOpt.ShowInConsole();

        }
    }
}

At the end of Main() _dExcludedPaths will have two of its keys exactly equal to each other.

Can someone help in understanding what is going on here and how is it possible to have duplicate keys in a dictionary??

Thanks

Answer 1

    public int Compare(string X, string Y) 
    {  
        int nXSlashes = SlashCounter(X); 
        int nYSlashes = SlashCounter(Y); 

        if (nXSlashes > nYSlashes)
          return -1;
        if (nXSlashes < nYSlashes)
          return 1;

        return string.Compare(X, Y, true);          
    }