f# 检查目录是否可访问 不工作

Question

try (box (Directory.GetDirectories(dir) ))
with | :? System.UnauthorizedAccessException -> () 

我正在尝试检查该目录是否可访问，这样我就不会收到“访问被拒绝”错误，但它不起作用，它没有跳过 for 中的循环

Answer 1

通常不鼓励将异常用作控制流的一部分。最好在尝试枚举其内容之前检查对目录的适当访问权限。尝试这样的事情:

open System
open System.IO
open System.Linq
open System.Security.AccessControl
open System.Security.Principal

let checkSecurity  =
    let account = sprintf @"%s\%s" Environment.UserDomainName Environment.UserName
    let identity = WindowsIdentity.GetCurrent()
    let principal = identity |> WindowsPrincipal
    let isAdmin = identity.Owner = identity.User
    fun (dir: DirectoryInfo) ->
        try
            let acl = dir.GetAccessControl(AccessControlSections.All)
            let rules = acl.GetAccessRules(true, true, typeof<NTAccount>)
            rules.OfType<FileSystemAccessRule>() 
            |> Seq.filter (fun rule -> rule.IdentityReference.Value.Equals(account, StringComparison.CurrentCultureIgnoreCase) || 
                           (if rule.IdentityReference.Value.Equals("BUILTIN\Administrators", StringComparison.CurrentCultureIgnoreCase) 
                            then isAdmin && principal.IsInRole(rule.IdentityReference.Value)
                            else principal.IsInRole(rule.IdentityReference.Value)))
            |> Seq.exists (fun rule -> (rule.FileSystemRights &&& FileSystemRights.Read = FileSystemRights.Read) && rule.AccessControlType <> AccessControlType.Deny)
        with | _ -> 
            false

let rec getFiles (dir: DirectoryInfo) =
    [ if checkSecurity dir
      then for file in dir.GetFiles("*") do yield file
           for subDir in dir.GetDirectories("*") do yield! getFiles subDir
    ]

let dir = DirectoryInfo(@"C:\Temp")
dir |> getFiles