借鉴SpringC#如何构建分布式锁

在.NET Core中，我们可以使用Microsoft.Extensions.Caching.Memory包来实现分布式锁

首先，安装Microsoft.Extensions.Caching.Memory包：

dotnet add package Microsoft.Extensions.Caching.Memory

接下来，创建一个DistributedLock类，实现分布式锁的功能：

using System;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Caching.Memory;

public class DistributedLock
{
    private readonly IMemoryCache _cache;
    private readonly TimeSpan _lockTimeout;

    public DistributedLock(IMemoryCache cache, TimeSpan lockTimeout)
    {
        _cache = cache;
        _lockTimeout = lockTimeout;
    }

    public async Task<bool> TryLockAsync(string lockKey, string requestId)
    {
        var cacheOptions = new MemoryCacheOptions();
        cacheOptions.ExpirationRelativeToNow = _lockTimeout;

        while (true)
        {
            var lockValue = Guid.NewGuid().ToString();
            var lockExists = await _cache.TryGetValueAsync(lockKey);

            if (!lockExists || (lockExists && lockValue != requestId))
            {
                if (_cache.Set(lockKey, lockValue, cacheOptions))
                {
                    return true;
                }
            }

            await Task.Delay(100);
        }
    }

    public async Task UnlockAsync(string lockKey, string requestId)
    {
        var cacheOptions = new MemoryCacheOptions();
        cacheOptions.ExpirationRelativeToNow = _lockTimeout;

        var lockValue = await _cache.TryGetValueAsync(lockKey);

        if (lockValue != null && lockValue.ToString() == requestId)
        {
            _cache.Remove(lockKey);
        }
    }
}

在这个类中，我们使用了IMemoryCache接口来存储锁的值。TryLockAsync方法尝试获取锁，如果锁不存在或者已经被其他请求者持有，则等待一段时间后重试。UnlockAsync方法用于释放锁。

使用示例：

public class Program
{
    public static async Task Main(string[] args)
    {
        var memoryCache = new MemoryCache(new MemoryCacheOptions());
        var distributedLock = new DistributedLock(memoryCache, TimeSpan.FromSeconds(10));

        var requestId = Guid.NewGuid().ToString();

        // 尝试获取锁
        bool lockAcquired = await distributedLock.TryLockAsync("myLockKey", requestId);

        if (lockAcquired)
        {
            try
            {
                // 执行需要同步的操作
                Console.WriteLine("Lock acquired, performing operation...");
            }
            finally
            {
                // 释放锁
                await distributedLock.UnlockAsync("myLockKey", requestId);
            }
        }
        else
        {
            Console.WriteLine("Failed to acquire lock, please try again.");
        }
    }
}

请注意，这个示例仅用于演示目的，实际生产环境中可能需要考虑更多的因素，例如使用Redis或其他分布式缓存系统来实现真正的分布式锁。