使用.NET标准库实现内存缓存机制的详细过程

using System;
using System.Runtime.Caching;
class Program
{
    private static readonly MemoryCache Cache = MemoryCache.Default;
    static void Main()
    {
        // 添加缓存项，设置5分钟绝对过期时间
        var policy = new CacheItemPolicy
        {
            AbsoluteExpiration = DateTimeOffset.Now.AddMinutes(5)
        };
        Cache.Add("my_cache_key", "缓存的值", policy);
        // 获取缓存值
        if (Cache.Contains("my_cache_key"))
        {
            var value = Cache.Get("my_cache_key");
            Console.WriteLine($"从缓存获取: {value}");
        }
        // 移除缓存项
        Cache.Remove("my_cache_key");
    }
}

public class DataService
{
    private static readonly MemoryCache Cache = MemoryCache.Default;
    public string GetExpensiveData(string key)
    {
        if (Cache.Contains(key))
        {
            return Cache.Get(key) as string;
        }
        // 模拟耗时操作
        var data = ExpensiveDatabaseCall(key);
        var policy = new CacheItemPolicy
        {
            SlidingExpiration = TimeSpan.FromMinutes(10),
            RemovedCallback = arguments =>
            {
                Console.WriteLine($"缓存项 {arguments.CacheItem.Key} 被移除，原因: {arguments.RemovedReason}");
            }
        };
        Cache.Add(key, data, policy);
        return data;
    }
    private string ExpensiveDatabaseCall(string key)
    {
        // 模拟数据库查询
        Thread.Sleep(2000);
        return $"数据库查询结果 for {key}";
    }
}

// 创建文件依赖的缓存项
var filePaths = new List<string> { @"C:\data\config.xml" };
var policy = new CacheItemPolicy
{
    ChangeMonitors = { new HostFileChangeMonitor(filePaths) }
};
Cache.Add("config_data", LoadConfig(), policy);

// 获取当前缓存统计信息
var cacheStats = Cache.GetCount();
Console.WriteLine($"当前缓存项数量: {cacheStats}");
// 设置内存限制（单位：字节）
var cacheSettings = new NameValueCollection
{
    { "cacheMemoryLimitMegabytes", "100" }, // 100MB
    { "physicalMemoryLimitPercentage", "50" } // 物理内存50%
};
var customCache = new MemoryCache("CustomCache", cacheSettings);

// 创建命名缓存实例
var userCache = new MemoryCache("UserCache");
var productCache = new MemoryCache("ProductCache");
// 在不同缓存中存储数据
userCache.Add("user_123", GetUser(123), policy);
productCache.Add("product_456", GetProduct(456), policy);