.Net Core 缓存方式（二）自定义分布式缓存的扩展方法（5）

IDistributedCache 的扩展方法

IDistributedCache 的扩展方法实现了类似于 cache.GetString(key); 这种写法，但是实际使用起来还需要写多行 类转字符串的代码，这时候就可以自己自定义 IDistributedCache 的扩展方法。

实现类似 MemoryCache的GetOrCreate方法

_cache.GetOrCreate

    var cacheEntry = _cache.GetOrCreate(CacheKeys.Entry, entry =>     {         entry.SlidingExpiration = TimeSpan.FromSeconds(3);         return DateTime.Now;     }); 

MemoryCache的GetOrCreate好用，看下实现方法：

        public static TItem GetOrCreate<TItem>(this IMemoryCache cache, object key, Func<ICacheEntry, TItem> factory)         {             if (!cache.TryGetValue(key, out object result))             {                 ICacheEntry entry = cache.CreateEntry(key);                 result = factory(entry);                 entry.SetValue(result);                 // need to manually call dispose instead of having a using                 // in case the factory passed in throws, in which case we                 // do not want to add the entry to the cache                 entry.Dispose();             }              return (TItem)result;         } 

我们可以写个类似 GetOrCreate 的扩展方法

        public static TItem GetOrCreate<TItem>(this IDistributedCache cache, string key, Func<TItem> factory, DistributedCacheEntryOptions options)         {             if (!cache.TryGetValue(key, out TItem obj))             {                 obj = factory();                 cache.Set(key, obj, options);             }             return (TItem)obj;         } 

自定义分布式缓存的扩展方法

我这里设置默认 半小时过期

    public static class DistributedCacheExtensions     {         private static readonly DistributedCacheEntryOptions DefaultOptions = new DistributedCacheEntryOptions().SetAbsoluteExpiration(TimeSpan.FromMinutes(30));          public static TItem Get<TItem>(this IDistributedCache cache, string key)         {             try             {                 var valueString = cache.GetString(key);                  if (string.IsNullOrEmpty(valueString))                 {                     return default(TItem);                 }                  return JsonSerializer.Deserialize<TItem>(valueString);             }             catch (Exception e)             {                 return default(TItem);             }         }          public static async Task<TItem> GetAsync<TItem>(this IDistributedCache cache, string key, CancellationToken token = default(CancellationToken))         {             try             {                 var valueString = await cache.GetStringAsync(key, token);                  if (string.IsNullOrEmpty(valueString))                 {                     return default(TItem);                 }                  return JsonSerializer.Deserialize<TItem>(valueString);             }             catch (Exception e)             {                 return default(TItem);             }         }          public static bool TryGetValue<TItem>(this IDistributedCache cache, string key, out TItem value)         {             var valueString = cache.GetString(key);             if (!string.IsNullOrEmpty(valueString))             {                 value = JsonSerializer.Deserialize<TItem>(valueString);                 return true;             }             value = default(TItem);             return false;         }          public static void Set<TItem>(this IDistributedCache cache, string key, TItem value)         {             cache.SetString(key, JsonSerializer.Serialize(value), DefaultOptions);         }          public static void Set<TItem>(this IDistributedCache cache, string key, TItem value, DistributedCacheEntryOptions options)         {             cache.SetString(key, JsonSerializer.Serialize(value), options);         }          public static async Task SetAsync<TItem>(this IDistributedCache cache, string key, TItem value, CancellationToken token = default(CancellationToken))         {             await cache.SetStringAsync(key, JsonSerializer.Serialize(value), DefaultOptions, token);         }          public static async Task SetAsync<TItem>(this IDistributedCache cache, string key, TItem value, DistributedCacheEntryOptions options, CancellationToken token = default(CancellationToken))         {             await cache.SetStringAsync(key, JsonSerializer.Serialize(value), options, token);         }          public static TItem GetOrCreate<TItem>(this IDistributedCache cache, string key, Func<TItem> factory)         {             if (!cache.TryGetValue(key, out TItem obj))             {                 obj = factory();                 cache.Set(key, obj);             }             return (TItem)obj;         }          public static TItem GetOrCreate<TItem>(this IDistributedCache cache, string key, Func<TItem> factory, DistributedCacheEntryOptions options)         {             if (!cache.TryGetValue(key, out TItem obj))             {                 obj = factory();                 cache.Set(key, obj, options);             }             return (TItem)obj;         }          public static async Task<TItem> GetOrCreateAsync<TItem>(this IDistributedCache cache, string key, Func<Task<TItem>> factory)         {             if (!cache.TryGetValue(key, out TItem obj))             {                 obj = await factory();                 await cache.SetAsync(key, obj);             }             return (TItem)obj;         }          public static async Task<TItem> GetOrCreateAsync<TItem>(this IDistributedCache cache, string key, Func<Task<TItem>> factory, DistributedCacheEntryOptions options)         {             if (!cache.TryGetValue(key, out TItem obj))             {                 obj = await factory();                 await cache.SetAsync(key, obj, options);             }             return (TItem)obj;         }     } 

用法 example：

        private readonly IDistributedCache _distributedCache;         public CategoryService(             IDistributedCache distributedCache)         {             _distributedCache = distributedCache;         }          public async Task<List<CategoryList>> GetCategoryList()         {             return await _distributedCache.GetOrCreateAsync(ProductCaching.GetCategoryList,                  async () => await GetFormHybris());         }              var saveCode = _distributedCache.Get<string>(cacheKey);             var order= _distributedCache.Get<Order>(cacheKey);