web api startup add imemory cache object

        #region cached data
       
        private IMemoryCache _cache;
        public HomeController(IMemoryCache memoryCache)
        {
            _cache = memoryCache;
        }
        public static class CacheKeys
        {
            public static string Entry { get { return "_Entry"; } }
            public static string CallbackEntry { get { return "_Callback"; } }
            public static string CallbackMessage { get { return "_CallbackMessage"; } }
            public static string Parent { get { return "_Parent"; } }
            public static string Child { get { return "_Child"; } }
            public static string DependentMessage { get { return "_DependentMessage"; } }
            public static string DependentCTS { get { return "_DependentCTS"; } }
            public static string Ticks { get { return "_Ticks"; } }
            public static string CancelMsg { get { return "_CancelMsg"; } }
            public static string CancelTokenSource { get { return "_CancelTokenSource"; } }
        }
        public IActionResult CacheTryGetValueSet()
        {
            DateTime cacheEntry;

            // Look for cache key.
            if (!_cache.TryGetValue(CacheKeys.Entry, out cacheEntry))
            {
                // Key not in cache, so get data.
                cacheEntry = DateTime.Now;

                // Set cache options.
                var cacheEntryOptions = new MemoryCacheEntryOptions()
                    // Keep in cache for this time, reset time if accessed.
                    .SetSlidingExpiration(TimeSpan.FromSeconds(3));

                // Save data in cache.
                _cache.Set(CacheKeys.Entry, cacheEntry, cacheEntryOptions);
            }

            return View("Cache", cacheEntry);
        }
        #endregion