Directory.GetFiles - different output dependent on OS

Question

I have a simple program. It runs .NET 4.5 and is built in Visual Studio 2013.

D:\\MyDir is full of .xlsx files and no .xls files. When I run the program on Windows 8.1 x64, the filter for *.xls returns no results. When I run the same program, with the same .NET version on Windows 7 x86, the *.xls filter returns the same results as the *.xlsx filter.

The test folders on both systems definitely contain the same data.

Am I missing something, or is this a bug in .NET and/or Windows?

The respective code:

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

namespace throw_test
{
    static class Program
    {
        static void Main()
        {
            int fileCount1 = Directory.GetFiles("D:\\MyDir", "*.xlsx").Length;
            int fileCount2 = Directory.GetFiles("D:\\MyDir", "*.xls").Length;

            Console.WriteLine("File Count 1: " + fileCount1);
            Console.WriteLine("File Count 2: " + fileCount2);

            Console.Read();
        }
    }
}

Edit 1

When I navigate to the directory using the command prompt in Windows 8.1 x64:

• dir *.xlsx returns all files as expected
• dir *.xls returns 'File Not Found'

Windows 7 returns the expected files on both of the above commands.

My guess is that .NET uses this command under the hood, thus the above results?

Answer 1

I tried on my machine with *.xls and all xlsx files are returned, just as described by MDSN.

I have Visual Studio 2013, built as Debug/Release Any CPU on .NET 4.5, and run on Win 8.1 X64 against NTFS/FAT32 partition, should cover your environment. Do you have anything else special?

EDIT

According to this question, you may have disabled 8.3 naming on your Win 8.1 System by running:

fsutil behavior set disable8dot3

You can query the current status by running

fsutil behavior query disable8dot3 <VolumePath>

On my machine it returns default setting like:

The volume state is: 0 (8dot3 name creation is enabled).
The registry state is: 2 (Per volume setting - the default).

Based on the above two settings, 8dot3 name creation is enabled on c: