C# 实现带过期时间的本地缓存工具

基于Dictionary和定时清理机制，实现支持自动过期的本地缓存，避免内存溢出。
using System.Collections.Concurrent;
using System.Timers;

public class ExpirableLocalCache
{
// 线程安全字典存储缓存项
private readonly ConcurrentDictionary _cache = new();
// 定时清理器（每分钟检查一次）
private readonly Timer _cleanupTimer;
private readonly object _lockObj = new();

public ExpirableLocalCache()
{
    _cleanupTimer = new Timer(60000);
    _cleanupTimer.Elapsed += OnCleanupTimerElapsed;
    _cleanupTimer.Start();
}

// 缓存项模型
private class CacheItem
{
    public object Value { get; set; }
    public DateTime ExpireTime { get; set; }
    public bool IsExpired => DateTime.Now > ExpireTime;
}

// 添加缓存（设置过期时间）
public void Set(string key, object value, TimeSpan expireAfter)
{
    _cache[key] = new CacheItem
    {
        Value = value,
        ExpireTime = DateTime.Now.Add(expireAfter)
    };
}

// 获取缓存
public T Get<T>(string key) where T : class
{
    if (_cache.TryGetValue(key, out var item) && !item.IsExpired)
    {
        return item.Value as T;
    }
    _cache.TryRemove(key, out _);
    return null;
}

// 主动移除缓存
public void Remove(string key)
{
    _cache.TryRemove(key, out _);
}

// 定时清理过期缓存
private void OnCleanupTimerElapsed(object sender, ElapsedEventArgs e)
{
    lock (_lockObj)
    {
        var expiredKeys = _cache.Where(kv => kv.Value.IsExpired)
                               .Select(kv => kv.Key)
                               .ToList();

        foreach (var key in expiredKeys)
        {
            _cache.TryRemove(key, out _);
        }
        Console.WriteLine($"清理了 {expiredKeys.Count} 个过期缓存项");
    }
}

// 调用示例
public static void TestCache()
{
    var cache = new ExpirableLocalCache();
    // 缓存5分钟
    cache.Set("user_1", new { Id = 1, Name = "张三" }, TimeSpan.FromMinutes(5));
    var user = cache.Get<dynamic>("user_1");
    Console.WriteLine($"获取缓存：{user?.Name}");
}

}