可以在不同的线程上等待任务完成吗?[副本]

您需要同步对CalculateSha256方法的访问,一次只有一个线程执行它。
自从 lock does not play nicely with async 您可以使用 SemaphoreSlim

private static readonly SemaphoreSlim _semaphoreSlim = new SemaphoreSlim(1, 1);

和使用 WaitAsync 方法(并且在完成时不要忘记释放它,使用finally block):

public async Task<string> Get(string value)
{
    await _semaphoreSlim.WaitAsync();
    try
    {
        return await CalculateSha256(value);
    }
    finally
    { 
        _semaphoreSlim.Release();
    }
}

protected async Task<T> GetConsecutively(Func<Task<T>> taskFactory)
{
    await _semaphoreSlim.WaitAsync();
    try
    {
        return await taskFactory();
    }
    finally
    { 
        _semaphoreSlim.Release();
    }
}

并修改Get方法以向其传递lambda表达式:

public async Task<string> Get(string value)
{
    return await GetConsecutively(() => CalculateSha256(value));
}

或者使用Stephen Cleary的 AsyncLock 而不是 它支持更接近 声明:

private static readonly AsyncLock _asyncLock = new AsyncLock();

public async Task<string> Get(string value)
{
    //Notice the use of using block
    //instead of try and finally 
    using(await _asyncLock.LockAsync())
    {
        return await CalculateSha256(value);
    }
}