上一节讲到Net Core 应用 Redis 在单一或小型的站点中，往往应用不到Redis这个量级的缓存服务器，这时候，一般倾向于本地的memory 缓存

MemoryCache

startup.cs

首先，在ConfigureServices方法中增加配置：

public void ConfigureServices(IServiceCollection services)
{
	services.AddMvc();
 
	services.AddMemoryCache();
}

HomeController

public class HomeController : Controller
{
	private readonly IMemoryCache _memoryCache;
 
	public HomeController(IMemoryCache memoryCache)
	{
		_memoryCache = memoryCache;
	}
 
	[HttpGet]
	public string Get()
	{
		var cacheKey = "TheTime";
		DateTime existingTime;
		if (_memoryCache.TryGetValue(cacheKey, out existingTime))
		{
			return "Fetched from cache : " + existingTime.ToString();
		}
		else
		{
			existingTime = DateTime.UtcNow;
			_memoryCache.Set(cacheKey, existingTime);
			return "Added to cache : " + existingTime;
		}
	}
}

memory cache 还有以下几个特性：

缓存过期时执行的方法 PostEvictionCallback

_memoryCache.Set(cacheKey, existingTime, 
	new MemoryCacheEntryOptions()
		.RegisterPostEvictionCallback((key, value, reason, state) => {  /*Do Something Here */ })
 );

缓存失效 CancellationToken ，不常用

var cts = new CancellationTokenSource();
_memoryCache.Set(cacheKey, existingTime, 
	new MemoryCacheEntryOptions()
		.AddExpirationToken(new CancellationChangeToken(cts.Token))
 );

Distributed Memory Cache

Distributed Memory Cache 可以看做是向RedisDistributedCache 的一个过渡方案，它的用法也与RedisDistributedCache 基本相同

startup.cs

public void ConfigureServices(IServiceCollection services)
{
	services.AddMvc();
 
	services.AddDistributedMemoryCache();
}

DistributedController

public class DistributedController : Controller
{
	private readonly IDistributedCache _distributedCache;
 
	public DistributedController(IDistributedCache distributedCache)
	{
		_distributedCache = distributedCache;
	}
 
	[HttpGet]
	public async Task<string> Get()
	{
		var cacheKey = "TheTime";
		var existingTime = _distributedCache.GetString(cacheKey);
		if (!string.IsNullOrEmpty(existingTime))
		{
			return "Fetched from cache : " + existingTime;
		}
		else
		{
			existingTime = DateTime.UtcNow.ToString();
			_distributedCache.SetString(cacheKey, existingTime);
			return "Added to cache : " + existingTime;
		}
	}
}

需要注意的是，IDistributedCache无法应用PostEvictionCallback 和CancellationTokens 这两个特性