How can i limit the access to file IO?
Im using C#, the code is executing on the local machine

i can enable access to file IO with:
PermissionSet ssc = new PermissionSet(null);
ssc.AddPermission(new
SecurityPermission(SecurityPermissionFlag.Execution));
ssc.AddPermission(new FileIOPermission(PermissionState.Unrestricted));

i can disable it by not setting it or setting it to:
ssc.AddPermission(new FileIOPermission(PermissionState.None));

but i would prefer a middleground, alow it only to read for example and
perhaps limit it to a certin directory.

i have found that FileIOPermission has the overload:
FileIOPermission(System.Security.Permissions.FileIOPermissionAccess
access, string path)

this would apear to be what im looking for, as the
FileIOPermissionAccess value can be read and i would assume the string
would be the path its allowed to read from...

however when i try to set this i get:
Request for the permission of type
'System.Security.Permissions.FileIOPermission, mscorlib,
Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'
failed.

this is using:
ssc.AddPermission(new FileIOPermission( FileIOPermissionAccess.Read,
Application.StartupPath + "\\Data\\"));

i dnt see why this request is being refused as if i set it to
Unrestricted it gets granted...
unless im misunderstanding the purpose of this method?

any ideas?