System.IO.MemoryStream.CopyToAsync C# (CSharp) Method

        public override Task CopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken)
        {
            // This implementation offers better performance compared to the base class version.
            
            StreamHelpers.ValidateCopyToArgs(this, destination, bufferSize);

            // If we have been inherited into a subclass, the following implementation could be incorrect
            // since it does not call through to ReadAsync() which a subclass might have overridden.  
            // To be safe we will only use this implementation in cases where we know it is safe to do so,
            // and delegate to our base class (which will call into ReadAsync) when we are not sure.
            if (GetType() != typeof(MemoryStream))
            {
                return base.CopyToAsync(destination, bufferSize, cancellationToken);
            }

            return CopyToAsyncImpl(destination, bufferSize, cancellationToken);
        }

        /// <summary>
        /// Save the current <see cref="SessionState"/>.  Any <see cref="Frame"/> instances
        /// registered with <see cref="RegisterFrame"/> will also preserve their current
        /// navigation stack, which in turn gives their active <see cref="Page"/> an opportunity
        /// to save its state.
        /// </summary>
        /// <returns>An asynchronous task that reflects when session state has been saved.</returns>
        public static async Task SaveAsync()
        {
            try
            {
                // Save the navigation state for all registered frames
                foreach (var weakFrameReference in _registeredFrames)
                {
                    Frame frame;
                    if (weakFrameReference.TryGetTarget(out frame))
                    {
                        SaveFrameNavigationState(frame);
                    }
                }

                // Serialize the session state synchronously to avoid asynchronous access to shared
                // state
                MemoryStream sessionData = new MemoryStream();
                DataContractSerializer serializer = new DataContractSerializer(typeof(Dictionary<string, object>), _knownTypes);
                serializer.WriteObject(sessionData, _sessionState);

                // Get an output stream for the SessionState file and write the state asynchronously
                StorageFile file = await ApplicationData.Current.LocalFolder.CreateFileAsync(sessionStateFilename, CreationCollisionOption.ReplaceExisting);
                using (Stream fileStream = await file.OpenStreamForWriteAsync())
                {
                    sessionData.Seek(0, SeekOrigin.Begin);
                    await sessionData.CopyToAsync(fileStream);
                }
            }
            catch (Exception e)
            {
                throw new SuspensionManagerException(e);
            }
        }