.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);

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