.Net Core 中 MemoryCache 使用

1.Demo，实际项目中不这么使用

class Program

{

static void Main(string[] args)

{

//缓存的配置

MemoryCacheOptions cacheOps = new MemoryCacheOptions()

{

//缓存最大为100份

//##注意netcore中的缓存是没有单位的，缓存项和缓存的相对关系

SizeLimit = 100,

//缓存满了时，压缩20%（即删除20份优先级低的缓存项）

CompactionPercentage = 0.2,

//两秒钟查找一次过期项

ExpirationScanFrequency = TimeSpan.FromSeconds(3)

};

MemoryCache myCache = new MemoryCache(cacheOps);

//单个缓存项的配置

MemoryCacheEntryOptions cacheEntityOps = new MemoryCacheEntryOptions()

{

//绝对过期时间1

//AbsoluteExpiration = new DateTimeOffset(DateTime.Now.AddSeconds(2)),

//绝对过期时间2

//AbsoluteExpirationRelativeToNow=TimeSpan.FromSeconds(3),

//相对过期时间

SlidingExpiration = TimeSpan.FromSeconds(3),

//优先级，当缓存压缩时会优先清除优先级低的缓存项

Priority = CacheItemPriority.Low,//Low,Normal,High,NeverRemove

//缓存大小占1份

Size = 1

};

//注册缓存项被清除时的回调，可以注册多个回调

cacheEntityOps.RegisterPostEvictionCallback((key, value, reason, state) =>

{

Console.WriteLine($"回调函数输出【键:{key},值:{value},被清除的原因:{reason}】");

});

myCache.Set("mykey", "myvalue", cacheEntityOps);

Console.WriteLine($"mykey的值：{myCache.Get("mykey") ?? "mykey缓存被清除了"}");

Console.WriteLine("------------------暂停3秒");

Thread.Sleep(3000);

Console.WriteLine($"mykey的值：{myCache.Get("mykey") ?? "mykey缓存被清除了"}");

Console.ReadKey();

}

}

}

 2. 注入（每个要用的Controller 都要构造很麻烦）

Startup.cs

public void ConfigureServices(IServiceCollection services)

{

services.AddMemoryCache();

// Add framework services.

services.AddMvc();

}

HomeController.cs

public class HomeController : Controller

{

private IMemoryCache _memoryCache;

public HomeController(IMemoryCache memoryCache)

{

_memoryCache = memoryCache;

}

public IActionResult Index()

{

string cacheKey = "key";

string result;

if (!_memoryCache.TryGetValue(cacheKey, out result))

{

result = $"LineZero{DateTime.Now}";

_memoryCache.Set(cacheKey, result);

}

ViewBag.Cache = result;

return View();

}

}

protected MemoryCacheEntryOptions EntryOptions

{

get

{

return new MemoryCacheEntryOptions()

{

//绝对过期时间1

//AbsoluteExpiration = new DateTimeOffset(DateTime.Now.AddSeconds(2)),

//绝对过期时间2

//AbsoluteExpirationRelativeToNow=TimeSpan.FromSeconds(3),

//相对过期时间

SlidingExpiration = TimeSpan.FromSeconds(10),

//优先级，当缓存压缩时会优先清除优先级低的缓存项

Priority = CacheItemPriority.Low,//Low,Normal,High,NeverRemove

//缓存大小占1份

Size = 1

};

}

}

//后面可以加 entryOptions 策略

_memoryCache.Set(cacheKey, result,entryOptions);

3.建个共用类

public class CacheCenter

{

public static MemoryCacheProvider MemoryCacheProvider { get; set; }

//.....可加其它类

}

Startup.cs

public void ConfigureServices(IServiceCollection services)

{

CacheCenter.MemoryCacheProvider = new MemoryCacheProvider();

// Add framework services.

}

MemoryCacheProvider.cs

public class MemoryCacheProvider

{ //外面可以直接调它

public MemoryCache MemoryCache { get; set; }

public MemoryCacheProvider()

{

MemoryCacheOptions cacheOps = new MemoryCacheOptions()

{

//缓存最大为100份

//##注意netcore中的缓存是没有单位的，缓存项和缓存的相对关系

SizeLimit = 100,

//缓存满了时，压缩20%（即删除20份优先级低的缓存项）

CompactionPercentage = 0.2,

//3秒钟查找一次过期项

ExpirationScanFrequency = TimeSpan.FromSeconds(3)

};

MemoryCache = new MemoryCache(cacheOps);

}

public object Get(string key)

{

return MemoryCache.Get(key);

}

public object Set(string key, int seconds)

{

var options = new MemoryCacheEntryOptions()

{

//绝对过期时间1

//AbsoluteExpiration = new DateTimeOffset(DateTime.Now.AddSeconds(2)),

//绝对过期时间2

//AbsoluteExpirationRelativeToNow=TimeSpan.FromSeconds(3),

//相对过期时间

SlidingExpiration = TimeSpan.FromSeconds(seconds),

//优先级，当缓存压缩时会优先清除优先级低的缓存项

Priority = CacheItemPriority.Low,//Low,Normal,High,NeverRemove

//缓存大小占1份

Size = 1

};

return MemoryCache.Set(key, options);

}

}

调用

//设值

if (!CacheCenter.MemoryCacheProvider.MemoryCache.TryGetValue("mykey", out string timestamp))

{

CacheCenter.MemoryCacheProvider.Set("mykey", DateTime.Now.ToString(), 3);

}

//其它地方取值

CacheCenter.MemoryCacheProvider.MemoryCache.Get("mykey")

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