Question

FileStream fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read);

Arguments: << path >> Debugging resource
strings are unavailable. Often the key
and arguments provide sufficient
information to diagnose the problem.
See
http://go.microsoft.com/fwlink/?linkid=106663&Version=4.0.41108.0&File=mscorlib.dll&Key=FileSecurityState_OperationNotPermitted

The line of code above has an error [FileSecurityState_OperationNotPermitted]

Answer 1

It sounds like your application is running in partial trust. To use a FileStream, you’ll need to request elevated trust:

By default, Silverlight-based
applications run in partial trust,
which means they run within a security
sandbox. Sandboxed applications have
restricted access to the local
computer and are constrained in other
ways that help prevent malicious
behavior.

From the Silverlight 4 FileStream documentation (emphasis mine):

When it is called by an elevated-trust
application, exposes a Stream around
a file, supporting both synchronous
and asynchronous read and write
operations.

EDIT: You can set an application to require elevated trust by setting the “Require elevated trust when running outside the browser” in your Silverlight project settings.