[英]Caching task results - AsyncLazy does not contain a definition for GetAwaiter
我正在嘗試按照我遵循的教程放置一個緩存系統。 這個概念似乎很容易理解,但是在實現它時,我收到以下錯誤消息:
“AsyncLazy”不包含“GetAwaiter”的定義,並且最佳擴展方法重載“AwaitExtensions.GetAwaiter(TaskScheduler)”需要“TaskScheduler”類型的接收器
下面是我的代碼:
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;
}
}
}
自從我將我的方法聲明為異步之后,我並沒有真正明白什么是錯誤的,因此任何線索都會受到贊賞。
似乎您需要像這樣在asyncLazyValue
上調用GetValueAsync
var result = await asyncLazyValue.GetValueAsync();
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