如何在启动时将数据放入 MemoryCache? [英] How do I put data in a MemoryCache on startup?

问题描述

在启动时，我想为我的网络应用创建一个静态数据存储.所以我最终偶然发现了 Microsoft.Extensions.Caching.Memory.MemoryCache.构建使用MemoryCache的功能后，突然发现我存储的数据不可用.所以它们可能是两个独立的实例.

At startup, I want to create a store of static data for my web app. So I eventually stumbled onto Microsoft.Extensions.Caching.Memory.MemoryCache. After building the feature that uses the MemoryCache, I suddenly find the data I stored is not available. So they're probably two separate instances.

如何在 Startup 中访问将由我的 Web 应用程序的其余部分使用的 MemoryCache 实例?这就是我目前正在尝试的方式:

How do I access the MemoryCache instance in Startup that will be used by the rest of my web app? This is how I'm currently trying it:

public class Startup
{
    public Startup(IHostingEnvironment env)
    {
        //Startup stuff
    }

    public void ConfigureServices(IServiceCollection services)
    {
        //configure other services

        services.AddMemoryCache();

        var cache = new MemoryCache(new MemoryCacheOptions());
        var entryOptions = new MemoryCacheEntryOptions().SetPriority(CacheItemPriority.NeverRemove);

        //Some examples of me putting data in the cache
        cache.Set("entryA", "data1", entryOptions);
        cache.Set("entryB", data2, entryOptions);
        cache.Set("entryC", data3.Keys.ToList(), entryOptions);
    }

    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
    {
        //pipeline configuration
    }
}

以及我使用 MemoryCache 的控制器

And the Controller where I use the MemoryCache

public class ExampleController : Controller
{   
    private readonly IMemoryCache _cache;

    public ExampleController(IMemoryCache cache)
    {
        _cache = cache;
    }

    [HttpGet]
    public IActionResult Index()
    {
        //At this point, I have a different MemoryCache instance.
        ViewData["CachedData"] = _cache.Get("entryA");

        return View();
    }
}

如果这是不可能的，是否有更好/更简单的替代方案?在这种情况下，全局单例是否可行?

If this is not possible, is there perhaps a better/simpler alternative? Would a global Singleton work in this situation?

推荐答案

添加语句时

services.AddMemoryCache();

您实际上是在说您想要一个内存缓存单例，它可以像在控制器中那样在您注入 IMemoryCache 的任何地方得到解决.因此，您需要向创建的单例对象添加值，而不是创建新的内存缓存.您可以通过将您的配置方法更改为以下内容来执行此操作:

you were in effect saying that you wanted a memory cache singleton that would get resolved wherever you injected IMemoryCache as you did in your controller. So instead of creating a new memory cache, you need to add values to the singleton object that was created. You can do this by changing your Configure method to something like:

    public void Configure(IApplicationBuilder app, 
        IHostingEnvironment env, 
        ILoggerFactory loggerFactory,
        IMemoryCache cache )
{
    var entryOptions = new MemoryCacheEntryOptions().SetPriority(CacheItemPriority.NeverRemove);

    //Some examples of me putting data in the cache
    cache.Set("entryA", "data1", entryOptions);
    cache.Set("entryB", data2, entryOptions);
    cache.Set("entryC", data3.Keys.ToList(), entryOptions);
    //pipeline configuration
}

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