Checking file/folder access permission

Question

I get an UnautorizedAccessException running this code:

string[] fileList = Directory.GetFiles(strDir, strExt);

The exception occurs in c:\users\username\appdata How can I check if I have access permission (to list and read files) ?

Solution 1

First of all, I would manually check the permissions and see what blocks you and what doesn't. I am using something like this to check for permissions (for copy file):

AuthorizationRuleCollection acl = fileSecurity.GetAccessRules(true, true,typeof(System.Security.Principal.SecurityIdentifier));
bool denyEdit = false;
for (int x = 0; x < acl.Count; x++)
{
    FileSystemAccessRule currentRule = (FileSystemAccessRule)acl[x];
    AccessControlType accessType = currentRule.AccessControlType;
    //Copy file cannot be executed for "List Folder/Read Data" and "Read extended attributes" denied permission
    if (accessType == AccessControlType.Deny && (currentRule.FileSystemRights & FileSystemRights.ListDirectory) == FileSystemRights.ListDirectory)
    {
        //we have deny copy - we can't copy the file
        denyEdit = true;
        break;
    }
... more checks 
}

Also, there are some strange cases where a certain right on the folder changes the right for the files regardless of their individual permissions (will see if I can find what it is).

Solution 2

Check article on code project which is about the thing you need, the is class created for this : The purpose of this class is to provide a simple answer to a common question, "Do I have permission to Read or Write this file?".

A simple way to test individual access rights for a given file and user

Note: cannot post whole code over here because its too long.

Solution 3

First, call Directory.GetFiles for root directory. Catch UnauthorizedAccessException - if none, you have full access.

If caught - call the function for each subdir recursively, catch the exception, if caught - add such dir to list.

Write a recursive function with external list for forbidden dirs

Comments

[dahvyd]

That example is anything but simple.

[dahvyd]

@Quandary, I'd tend to disagree in general, but that specific example does fifty bazillion things with terrible code, when the OP was asking about one very specific requirement. Overkill IMHO.

[Thomas]

It can certainly be simplified.