Question

In my unit tests, I am using the following code to open a stream and write to it:

IsolatedStorageFile store = IsolatedStorageFile.GetUserStoreForApplication();
stream = m_store.OpenFile(filename, FileMode.Create);
...
stream.Flush();
stream.Close();
stream.Dispose();
store.Dispose()

The first time it succeeds, but the second time it fails with the following log output:
Additional information: Operation not permitted on IsolatedStorageFileStream.

The FileMode.Create enum constant is defined as:

Specifies that the operating system should create a new file. If the file already exists, it will be overwritten. Create is equivalent to requesting that if the file does not exist, use CreateNew; otherwise, use Truncate.

so it appears this is the correct constant.

I have found a few similar questions on stackoverflow such as
IsolatedStorageFileStream exception is throw when file is opened?

but they didn’t help. As suggested somewhere on the net (can’t find the link now), I tried deleting the file first if it existed, contrary to the enum comments, like below, but didn’t help either:

if (store.FileExists(filename))
{
   store.DeleteFile(filename);
}

QUESTION: What I am missing?

Thanks!

Answer 1

Firstly, you should really use a using statement instead of explicitly calling Close or Dispose – otherwise if there’s an exception, you won’t have closed the stream.

Secondly, I suspect the problem is that you haven’t disposed of the store itself. Try this:

using (var store = IsolatedStorageFile.GetUserStoreForApplication())
using (var stream = store.OpenFile(filename, FileMode.Create))
{
    ...
}