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| Dan |
I have code like the following to test for existence of a file. I know the
file is there, but File.Exists returns FALSE. The problem appears to be
that the file is in a directory beneath "My Documents". When I move it to a
directory directly under the root, File.Exists returns TRUE. So I tried
using FileIOPermission to give me rights to read it, but still no luck. Any
suggestions? Thanks...
FileIOPermission f = new
FileIOPermission(FileIOPermissionAccess.AllAccess, fileName);
if (!File.Exists(fileName))
throw new FileNotFoundException("Unable to construct
BinaryUploadFile object. File does not exist:\n\n" + fileName + "\n\n");
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| Nicholas Paldino [.NET/C# MVP] (VIP) |
Dan,
If you don't have access to the directory, then Exists will return
false, as you expected.
You are creating the permission to see if you can access the directory,
to prevent a false negative. However, you aren't doing anything to indicate
whether or not you have permission. Between the call to Exists, and the
construction of the permission, call Demand on the permission. It will
throw a SecurityException if you don't have access to the directory.
Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
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| Willy Denoyette [MVP] (VIP) |
If you (the windows identity running the code) don't have the right
permissions to the folder holding the file, File.Exists will return false,
as you are experiencing.
This is called "windows access security " based on the identity of the
caller.
You are confusing this security mechanism with .NET's "Code access security"
, this kind of security mechanism is based on the "code identity" (where did
the code came from - internet, intranet, codegroup , ...) NOT the windows
user identity, these are fundamentally different. Whatever you do in code
(that is Code Access Security) won't help if the "windows user" has no
access rights for the objects (like files) controlled by the OS security
system (Windows security).
In short you need to fix the NTFS security settings on the file/folder.
Willy.
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