缓存任务结果 - AsyncLazy 不包含 GetAwaiter 的定义

Question

我正在尝试按照我遵循的教程安装一个缓存系统。这个概念似乎很容易理解，但在实现它时，我收到以下错误消息：

“AsyncLazy”不包含“GetAwaiter”的定义，最佳扩展方法重载“AwaitExtensions.GetAwaiter(TaskScheduler)”需要“TaskScheduler”类型的接收器

下面是我的代码：

using System;
using System.Linq;
using System.Runtime.Caching;
using System.Threading.Tasks;
using Microsoft.VisualStudio.Threading;

public class TaskCache : ITaskCache
    {
        private MemoryCache _cache { get; } = MemoryCache.Default;
        private CacheItemPolicy _defaultPolicy { get; } = new CacheItemPolicy();

        public async Task<T> AddOrGetExisting<T>(string key, Func<Task<T>> valueFactory)
        {

            var asyncLazyValue = new AsyncLazy<T>(valueFactory);
            var existingValue = (AsyncLazy<T>)_cache.AddOrGetExisting(key, asyncLazyValue, _defaultPolicy);

            if (existingValue != null)
            {
                asyncLazyValue = existingValue;
            }

            try
            {
                var result = await asyncLazyValue; // ERROR HERE

                // The awaited Task has completed. Check that the task still is the same version
                // that the cache returns (i.e. the awaited task has not been invalidated during the await).    
                if (asyncLazyValue != _cache.AddOrGetExisting(key, new AsyncLazy<T>(valueFactory), _defaultPolicy))
                {
                    // The awaited value is no more the most recent one.
                    // Get the most recent value with a recursive call.
                    return await AddOrGetExisting(key, valueFactory);
                }
                return result;
            }
            catch (Exception)
            {
                // Task object for the given key failed with exception. Remove the task from the cache.
                _cache.Remove(key);
                // Re throw the exception to be handled by the caller.
                throw;
            }
        }
     }

由于我将我的方法声明为异步，因此我并没有真正理解问题所在。

Answer 1

您似乎需要在您的asyncLazyValue 上调用GetValueAsync，就像这样var result = await asyncLazyValue.GetValueAsync();