找不到文件之前处理未经授权的访问

Question

When someone wants to access a file in a shared folder, two issues might happen: first is that the user does not have permission to access a folder or file and second the file is not there! But I'm facing a problem in case of the user doesn't have access to the folder and the file is not in that folder. In this case, it has thrown a FileNotFoundException instead of UnauthorizedAccessException !
Below I wrote a bunch of code to handle these issues.
Solution 1: Use File.Exist

    static void Main(string[] args)
    {
        NetworkCredential nc = new NetworkCredential("Administartor", "xxx", "xxx");
        CredentialCache cc = new CredentialCache();
        cc.Add(new Uri(@"\\WIN-xxx"), "Basic", nc);
        var address_access_exist = @"\\WIN-xxx\Z-Test-A-E\file.txt";
        var address_access_not_exist = @"\\WIN-xxx\Z-Test-A-NE\file.txt";
        var address_not_access_exist = @"\\WIN-xxx\Z-Test-NA-E\file.txt";
        var address_not_access_not_exist = @"\\WIN-xxx\Z-Test-NA-NE\file.txt";
        Console.WriteLine(check(address_access_exist));
        Console.WriteLine(check(address_access_not_exist));
        Console.WriteLine(check(address_not_access_exist));
        Console.WriteLine(check(address_not_access_not_exist));
        Console.ReadLine();
    }

    public static string check(string address)
    {
        try
        {
            if (File.Exists(address))
            {
                return File.ReadAllText(address);
            }
            else
            {
                return "Not Exist!";
            }
        }
        catch (UnauthorizedAccessException e)
        {
            return e.Message;
        }
        catch (FileNotFoundException e)
        {
            return e.Message;
        }
    }

Output 1


Solution 2:

    static void Main(string[] args)
    {
        NetworkCredential nc = new NetworkCredential("Administartor", "xxx", "xxx");
        CredentialCache cc = new CredentialCache();
        cc.Add(new Uri(@"\\WIN-xxx"), "Basic", nc);
        var address_access_exist = @"\\WIN-xxx\Z-Test-A-E\file.txt";
        var address_access_not_exist = @"\\WIN-xxx\Z-Test-A-NE\file.txt";
        var address_not_access_exist = @"\\WIN-xxx\Z-Test-NA-E\file.txt";
        var address_not_access_not_exist = @"\\WIN-xxx\Z-Test-NA-NE\file.txt";
        Console.WriteLine(check(address_access_exist));
        Console.WriteLine(check(address_access_not_exist));
        Console.WriteLine(check(address_not_access_exist));
        Console.WriteLine(check(address_not_access_not_exist));
        Console.ReadLine();
    }

    public static string check(string address)
    {
        try
        {
            if (File.ReadAllText(address).Length >= 0)
            {
                return File.ReadAllText(address);
            }
            else
            {
                return "Not Exist!";
            }
        }
        catch (UnauthorizedAccessException e)
        {
            return e.Message;
        }
        catch (FileNotFoundException e)
        {
            return e.Message;
        }
    }

Output 2


So the main problem is that if a user doesn't have access to a specific folder and even the file is not there why it doesn't show Access Denied instead of File Not Found?
Thank you for your time :)

Answer 1

According to the documentation: UnauthorizedAccessException path specified a file that is read-only.

It makes me think that the method try to read the file (as path is correct), however it doesn't find the file, so it can't say that if file is read-only or not. Due to this it actually sends a file not found exception rather than the expected exception.