/// <summary>
/// Reads the cache data from the backend database.
/// </summary>
private void ReadCacheForSignedInUser(TokenCacheNotificationArgs args)
{
string accountId = httpContextAccesssor.HttpContext.User.GetMsalAccountId();
if (this.InMemoryCache == null) // first time access
{
this.InMemoryCache = GetLatestUserRecordQuery(accountId).FirstOrDefault();
}
else
{
// retrieve last written record from the DB
var lastwriteInDb = GetLatestUserRecordQuery(accountId).Select(n => n.LastWrite).FirstOrDefault();
// if the persisted copy is newer than the in-memory copy
if (lastwriteInDb > InMemoryCache.LastWrite)
{
// read from from storage, update in-memory copy
this.InMemoryCache = GetLatestUserRecordQuery(accountId).FirstOrDefault();
}
}
// Send data to the TokenCache instance
args.TokenCache.DeserializeMsalV3((InMemoryCache == null) ? null : this.DataProtector.Unprotect(InMemoryCache.CacheBits), shouldClearExistingCache: true);
}
/// <summary>
/// Raised AFTER MSAL added the new token in its in-memory copy of the cache.
/// This notification is called every time MSAL accessed the cache, not just when a write took place:
/// If MSAL's current operation resulted in a cache change, the property TokenCacheNotificationArgs.HasStateChanged will be set to true.
/// If that is the case, we call the TokenCache.Serialize() to get a binary blob representing the latest cache content – and persist it.
/// </summary>
/// <param name="args">Contains parameters used by the MSAL call accessing the cache.</param>
private void UserTokenCacheAfterAccessNotification(TokenCacheNotificationArgs args)
{
string accountId = args.Account?.HomeAccountId?.Identifier;
if (string.IsNullOrEmpty(accountId))
{
accountId = httpContextAccesssor.HttpContext.User.GetMsalAccountId();
}
// if state changed, i.e. new token obtained
if (args.HasStateChanged && !string.IsNullOrWhiteSpace(accountId))
{
if (this.InMemoryCache == null)
{
this.InMemoryCache = new UserTokenCache
{
WebUserUniqueId = accountId
};
}
this.InMemoryCache.CacheBits = this.DataProtector.Protect(args.TokenCache.SerializeMsalV3());
this.InMemoryCache.LastWrite = DateTime.Now;
try
{
// Update the DB and the lastwrite
this.TokenCacheDb.Entry(InMemoryCache).State = InMemoryCache.UserTokenCacheId == 0 ? EntityState.Added : EntityState.Modified;
this.TokenCacheDb.SaveChanges();
}
catch (DbUpdateConcurrencyException)
{
// Record already updated on a different thread, so just read the updated record
this.ReadCacheForSignedInUser(args);
}
}
}