Operation not permitted on IsolatedStorageFileStream

I have been trying to open a file on c: drive using Isolated Storage, I tried different ways but they all give the same error, here's the code;

IsolatedStorageFile ifs = IsolatedStorageFile.GetUserStoreForApplication();
Stream stream = new IsolatedStorageFileStream("avi.txt", FileMode.Open, Fil开发者_如何学CeAccess.Read, ifs);

I even tried:

1)

Stream stream = new IsolatedStorageFileStream(@"avi.txt", FileMode.Open, FileAccess.Read, ifs);

2)

Stream stream = new IsolatedStorageFileStream(@"files/avi.txt", FileMode.Open, FileAccess.Read, ifs);

3)

Stream stream = new IsolatedStorageFileStream("files/avi.txt", FileMode.Open, FileAccess.Read, ifs);

how can I open the file without using a Dialog box.

Thank you in advance

I can't explain the error you are seeing since I would gave expected to see file not found error.

It sounds to me that you are attempting to use isolated storage to access a file in the clients file system.

You need to be running an OOB with elevated trust. Then you can use System.IO.File to open a file and even then you are restricted to the MyDocuments area for the current user.

Outside of that you do need to show the user a dialog.