/// <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 AppTokenCacheAfterAccessNotification(TokenCacheNotificationArgs args)
{
// if state changed, i.e. new token obtained
if (args.HasStateChanged && !string.IsNullOrWhiteSpace(_activeClientId))
{
if (_inMemoryCache == null)
{
_inMemoryCache = new AppTokenCache
{
ClientID = _activeClientId
};
}
_inMemoryCache.CacheBits = _dataProtector.Protect(_apptokenCache.SerializeMsalV3());
_inMemoryCache.LastWrite = DateTime.Now;
try
{
// Update the DB and the lastwrite
_tokenCacheDb.Entry(_inMemoryCache).State = _inMemoryCache.AppTokenCacheId == 0 ? EntityState.Added : EntityState.Modified;
_tokenCacheDb.SaveChanges();
}
catch (DbUpdateConcurrencyException)
{
// Record already updated on a different thread, so just read the updated record
ReadCacheForSignedInApp();
}
}
}
/// <summary>
/// Reads the cache data from the backend database.
/// </summary>
private void ReadCacheForSignedInApp()
{
if (_inMemoryCache == null) // first time access
{
_inMemoryCache = GetLatestAppRecordQuery().FirstOrDefault();
}
else
{
// retrieve last written record from the DB
var lastwriteInDb = GetLatestAppRecordQuery().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
_inMemoryCache = GetLatestAppRecordQuery().FirstOrDefault();
}
}
// Send data to the TokenCache instance
_apptokenCache.DeserializeMsalV3((_inMemoryCache == null) ? null : _dataProtector.Unprotect(_inMemoryCache.CacheBits));
}