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) ?

Answer 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).