Sharing Folder Access in C#

 public class LockUnLock
    {
        [PermissionSet(SecurityAction.Demand, Name = "FullTrust")]
        public class LockUnlock : IDisposable
        {
            private readonly SafeTokenHandle _handle;
            private readonly WindowsImpersonationContext _context;

            const int LOGON32_LOGON_NEW_CREDENTIALS = 9;

            public LockUnlock(string domain, string username, string password)
            {
                var ok = LogonUser(username, domain, password,
                               LOGON32_LOGON_NEW_CREDENTIALS, 0, out this._handle);
                if (!ok)
                {
                    var errorCode = Marshal.GetLastWin32Error();
                    throw new ApplicationException(string.Format("Could not impersonate the elevated user.  LogonUser returned error code {0}.", errorCode));
                }

                this._context = WindowsIdentity.Impersonate(this._handle.DangerousGetHandle());
            }

            public void Dispose()
            {
                this._context.Dispose();
                this._handle.Dispose();
            }

            [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
            private static extern bool LogonUser(String lpszUsername, String lpszDomain, String lpszPassword, int dwLogonType, int dwLogonProvider, out SafeTokenHandle phToken);

            public sealed class SafeTokenHandle : SafeHandleZeroOrMinusOneIsInvalid
            {
                private SafeTokenHandle()
                    : base(true) { }

                [DllImport("kernel32.dll")]
                [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
                [SuppressUnmanagedCodeSecurity]
                [return: MarshalAs(UnmanagedType.Bool)]
                private static extern bool CloseHandle(IntPtr handle);

                protected override bool ReleaseHandle()
                {
                    return CloseHandle(handle);
                }
            }
        }
    }