获取超过 260 个字符的过长文件路径的安全信息：C#

Question

I am trying to get security information of some files and directories inside a network folder. Unfortunately some files and directories path exceed their character limits 260/248 respectively. I found so many information to use Win32 P/Invoke, use .NET Framework 4.6.2 etc. I was able to use a code by Kim Hamilton to iterate through each files and directories inside whose path exceeds the length limit but I could not use it to get the security information.

Below is my simple C# code containing a path which is above 260 characters. It will throw a Path Too Long Exception. Could you please help me solve it in this scenario.

using System.IO;
using System.Security.AccessControl;

namespace Microsoft.Experimental.IO
{
    class Program
    {
        public static void Main(string[] args)
        {
            string path = @"\\Domain\UserData\VeryLongPath";  //This is above 260 characters
            DirectoryInfo info = new DirectoryInfo(path);
            DirectorySecurity security = Directory.GetAccessControl(path);

        }
    }
}

Answer 1

Accepted answer didn't really work for me although I checked the registry key (it seems to be enabled by default nowadays). The exception thrown was as mentioned: invalid name, invalid parameter (happened on SetAccessControl in my case). .NET 4.7.2

What helped is the special syntax: \\\\?\\ for local paths or \\\\?\\UNC\\ for network shares.

So for the example in question (server share) it would be something like below:

var security = Directory.GetAccessControl($@"\\?\UNC\{path.TrimStart('\\')}");

Answer 2

I saw in some other posts that installing .NET Framework 4.6.2 does help. As the last resort, I tried it. I had Visual Studio 2015. I installed .NET Framework 4.6.2. It still did not work. Then I installed Visual Studio 2017 and chose .NET Framework 4.6.2 . It did eliminate Path Too Long Exception. But it gave a new exception called Invalid name, Invalid parameter.

One of my colleague suggested me to check the value of registry

Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem\LongPathsEnabled

It's original value was 0. I set it to 1. And both the Path Too Long and Invalid Name, Invalid parameter exception were gone. I believe this registry key does not exist in computer that does not have .NET Framework 4.6.2.