借鑒SpringC#如何構建分布式鎖

在.NET Core中，我們可以使用Microsoft.Extensions.Caching.Memory包來實現分布式鎖

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

dotnet add package Microsoft.Extensions.Caching.Memory

接下來，創建一個DistributedLock類，實現分布式鎖的功能：

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);
        }
    }
}

在這個類中，我們使用了IMemoryCache接口來存儲鎖的值。TryLockAsync方法嘗試獲取鎖，如果鎖不存在或者已經被其他請求者持有，則等待一段時間后重試。UnlockAsync方法用于釋放鎖。

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();

        // 嘗試獲取鎖
        bool lockAcquired = await distributedLock.TryLockAsync("myLockKey", requestId);

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

請注意，這個示例僅用于演示目的，實際生產環境中可能需要考慮更多的因素，例如使用Redis或其他分布式緩存系統來實現真正的分布式鎖。