Question

While working on a project today I ran into this odd behavior in .NET.

I’m grabbing a list of file names and adding them to an object. However I need to filter the incoming names against a known list of “bad” names which led me to do this. (I’m by no means an advanced C# coder, still just learning it.) However, because it causes the aspnet_wp.exe process to run at 100% indefinitely, I assume that I’m doing something wrong with the language.

Here’s my code for reference:

List<string> localFiles = new List<string>(); 
// I was worried the object was causing the issue so dumbed it down to this with no changed.

string path = "//<file share>/<dir>/"; 
// As I commented below yes, it's slow when it works but it's clearly not working when using the if();

List<string> omitNames = new List<string>();
omitNames.Add("Thumbs.db"); 
// This is the only item in the list when it breaks also.

FileInfo[] localFileList = new DirectoryInfo(path).GetFiles();
foreach ( FileInfo item in localFileList )
{
    if(!omitNames.Contains(item.Name))
    {
        localFiles.Add(path + itemName);
    }
}

Can anyone explain why this code runs as an infinite loop? It looks like it really shouldn’t. Also, I realize that using a List may not be the best approach. Is there another way to implement this cleanly?

Commenting out the if(!){} for omitNames allows the code to run properly. (Though obviously the results are not filtered.)

UPDATE: It was requested to put this in a console app which you’ll find below. However it works perfectly. Another thing is that someone suggested that I try to simply compare it against a string. But the exact same thing happens if it’s changed to this:

if(item.Name != "Thumbs.db")
{
    localFiles.Add(path + itemName);
}

Console App (which works):

using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace LoopKiller
{
class Program
{

    static void Main(string[] args)
    {

        List<string> omitNames = new List<string>();
        List<string> localFiles = new List<string>();

        omitNames.Add("Thumbs.db");

        FileInfo[] localFileList = new DirectoryInfo("c:/test/").GetFiles();

        foreach (FileInfo item in localFileList)
        {
            if (!omitNames.Contains(item.Name))
            {
                Console.WriteLine("Adding " + item.Name + " to localFiles.");
                localFiles.Add(item.Name);
                Console.WriteLine("Item added to localFiles.");
            }
        }

        foreach (string item in localFiles)
        {
            Console.WriteLine(item);
        }

        Console.ReadLine();

    }
}
}

Answer 1

Is this any quicker?

foreach (string item in Directory.GetFiles("c:/test/", "*.*").Select(Path.GetFileName())
    {
        if (!omitNames.Contains(item))
        {
            Console.WriteLine("Adding " + item.Name + " to localFiles.");
            localFiles.Add(item.Name);
            Console.WriteLine("Item added to localFiles.");
        }
    }