.Net Core 缓存方式（一）内存缓存

.Net Core 缓存方式（一）内存缓存

使用 IMemoryCache

官方文档

• 官方文档
• 使用包 dotnet add package System.Runtime.Caching --version 4.7.0
• 使用方式

public class HomeController : Controller
{
    private IMemoryCache _cache;

    public HomeController(IMemoryCache memoryCache)
    {
        _cache = memoryCache;
    }

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);
}

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

    return View("Cache", cacheEntry);
}

public async Task<IActionResult> CacheGetOrCreateAsynchronous()
{
    var cacheEntry = await
        _cache.GetOrCreateAsync(CacheKeys.Entry, entry =>
        {
            entry.SlidingExpiration = TimeSpan.FromSeconds(3);
            return Task.FromResult(DateTime.Now);
        });

    return View("Cache", cacheEntry);
}

• 源码地址
  Microsoft.Extensions.Caching.Memory

GetOrCreate 实现原理

        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;
        }

        public static async Task<TItem> GetOrCreateAsync<TItem>(this IMemoryCache cache, object key, Func<ICacheEntry, Task<TItem>> factory)
        {
            if (!cache.TryGetValue(key, out object result))
            {
                ICacheEntry entry = cache.CreateEntry(key);
                result = await factory(entry).ConfigureAwait(false);
                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;
        }

https://github.com/dotnet/runtime/blob/master/src/libraries/Microsoft.Extensions.Caching.Memory/src/MemoryCache.cs