ShowEasy/EuroTran/WebApp/Outlook/TokenStorage/TokenStorage.cs

using Microsoft.Identity.Client;
using System.Threading;
using System.Web;

namespace WebApp.Outlook.TokenStorage
{
    public class SessionTokenCache
    {
        private static ReaderWriterLockSlim SessionLock = new ReaderWriterLockSlim(LockRecursionPolicy.NoRecursion);
        private string UserId = string.Empty;
        private string CacheId = string.Empty;
        private HttpContextBase httpContext = null;

        private TokenCache cache = new TokenCache();

        public SessionTokenCache(string userId, HttpContextBase httpcontext)
        {
            // not object, we want the SUB
            UserId = userId;
            CacheId = UserId + "_TokenCache";
            httpContext = httpcontext;
            Load();
        }

        public TokenCache GetMsalCacheInstance()
        {
            cache.SetBeforeAccess(BeforeAccessNotification);
            cache.SetAfterAccess(AfterAccessNotification);
            Load();
            return cache;
        }

        public void SaveUserStateValue(string state)
        {
            SessionLock.EnterWriteLock();
            httpContext.Session[CacheId + "_state"] = state;
            SessionLock.ExitWriteLock();
        }

        public string ReadUserStateValue()
        {
            var state = string.Empty;
            SessionLock.EnterReadLock();
            state = (string)httpContext.Session[CacheId + "_state"];
            SessionLock.ExitReadLock();
            return state;
        }

        public void Load()
        {
            SessionLock.EnterReadLock();
            cache.Deserialize((byte[])httpContext.Session[CacheId]);
            SessionLock.ExitReadLock();
        }

        public void Persist()
        {
            SessionLock.EnterWriteLock();

            // Optimistically set HasStateChanged to false. We need to do it early to avoid losing
            // changes made by a concurrent thread.
            cache.HasStateChanged = false;

            // Reflect changes in the persistent store
            httpContext.Session[CacheId] = cache.Serialize();
            SessionLock.ExitWriteLock();
        }

        // Triggered right before MSAL needs to access the cache. Reload the cache from the
        // persistent store in case it changed since the last access.
        private void BeforeAccessNotification(TokenCacheNotificationArgs args)
        {
            Load();
        }

        // Triggered right after MSAL accessed the cache.
        private void AfterAccessNotification(TokenCacheNotificationArgs args)
        {
            // if the access operation resulted in a cache update
            if (cache.HasStateChanged)
            {
                Persist();
            }
        }
    }
}