Run a .NET program from a mapped drive or shared folder

Question

I have written a C# Windows Forms application to merge the files and folders from a remote folder on one machine ("source" folder is a mapped drive - "Z:\folder") with another remote folder on a different machine ("destination" folder is a UNC path to a shared folder - "\\computername\sharedfolder"). I have Full permissions to both folders. When I run the program on my local machine, it works fine, but when I try to run it from from within the source folder it fails with a security exception.

The failure occurs when calling the DirectoryInfo constructor for the destination folder (i.e., DirectoryInfo(@"\\computername\sharedfolder"). I assume the problem is because I am running the program from a mapped drive. Any workarounds?

---

The specific exception is: Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.

Answer 1

Have you turned on impersonation in the app.config file? It could be that the application is being run as the other machine, and not the user starting the application.

Answer 2

.NET 3.5 SP1 allows running applications off a network share. Previous versions did not allow it.

Answer 3

You need to enable FullTrust permissions for the application. .NET applications that run on a network share are given Local Intranet security permissions and thus run in a sandbox.

Here is a batch file that I wrote for one of our testing apps that runs off the network. It should get you up and running with minor modifications.

@ECHO OFF
SET CASPOL=%windir%\Microsoft.NET\Framework\v2.0.50727\CasPol.exe
CLS

%CASPOL% -pp off
%CASPOL% -m -ag 1.2 -url file://server/directory/* FullTrust

As stated above, .NET 3.5 removes this behaviour.

Answer 4

Okay, I got my application into Visual Studio 2008 (it was previously coded in 2005), targeted the .NET 3.5 framework, compiled and tried again.

I got the exact same error.

---

I'm not sure how to turn on impersonation for the current user in app.config.

Answer 5

I tried it with .NET 3.5, and it didn't work, then I noticed that you said 3.5 SP1. The service pack is definately needed.

Problem solved. Thank you.