.NET Bot Framework SDK v4：同时间提醒重复发送自适应卡片的解决方法

问题现象 #

使用Bot Framework SDK v4在Teams频道实现提醒功能，提醒数据存储于SharePoint，通过定时器在预设时间拉取提醒并发送自适应卡片。当提醒设置为不同时间时，每个提醒对应一张卡片，功能正常；但创建n个同一时间的提醒时，会收到n*n张重复卡片，不符合预期。曾尝试用字典以ReminderId为键去重，但未生效。

相关代码 #

private async Task SetReminderTimer(ITurnContext turnContext, ReminderListDto reminderTask, DateTime dateTime, string userInputTimeZoneOffset)
{
    try
    {
        // Calculate the time until the reminder should trigger
        var delay = dateTime - DateTime.Now;

        _reminderTimer = new Timer(async _ =>
        {
            // Retrieve the reminder item from SharePoint
            var reminders = await _sharePointLogger.GetReminderFromSharePointAsync(reminderTask, userInputTimeZoneOffset);

            foreach (var reminder in reminders)
            {
                // If the reminder item exists and the reminder time is in the past, send the reminder message to the user
                if (reminder != null && DateTime.Now > reminderTask.Time)
                {
                    // Send a reminder message to the user
                    var conversationReference = turnContext.Activity.GetConversationReference();
                    await ((BotAdapter)turnContext.Adapter).ContinueConversationAsync(_botId, conversationReference, async (turnContext, cancellationToken) =>
                    {
                        var displayReminder = ReminderList.DisplayReminder(reminder.Time.ToString("HH:mm"), reminder.ReminderType, reminder.Priority, reminder.ReminderDetails);
                        var adaptiveCardAttachment = new Attachment()
                        {
                            ContentType = "application/vnd.microsoft.card.adaptive",
                            Content = JsonConvert.DeserializeObject(displayReminder),
                        };
                        await turnContext.SendActivityAsync(MessageFactory.Attachment(adaptiveCardAttachment), cancellationToken);
                    }, default);
                    //await DeleteReminderFromSharePointAsync(reminder.ReminderId);

                }
            }

        }, null, (int)delay.TotalMilliseconds, Timeout.Infinite);
    }
    catch (Exception ex)
    {
        _logger.LogInformation($"error at sedning reminder to user {ex.Message} ");
        throw;
    }

}

问题根源 #

1. 定时器重复创建：每创建一个同时间的提醒，就会调用一次SetReminderTimer，生成独立的定时器实例。当到达预设时间时，每个定时器都会执行回调逻辑，从SharePoint拉取所有同时间的提醒并逐个发送。例如创建3个同时间提醒，会生成3个定时器，每个定时器遍历3条提醒发送，最终产生9张重复卡片。
2. 去重逻辑无效：之前尝试的字典去重仅在单个定时器的回调内部生效，每个定时器的字典是独立实例，无法跨定时器去重；或者字典未持久化，每次回调执行时重新初始化，起不到全局去重作用。

解决方案 #

方案一：按时间维度聚合提醒，统一管理定时器 #

维护全局字典，按触发时间（标准化到分钟级别，避免毫秒差异）分组管理提醒列表和定时器实例，确保同一时间仅存在一个定时器：

// 全局字典，线程安全操作需加锁
private readonly Dictionary<DateTime, (List<ReminderListDto> Reminders, Timer Timer)> _timedReminders = new Dictionary<DateTime, (List<ReminderListDto>, Timer)>();

private async Task SetReminderTimer(ITurnContext turnContext, ReminderListDto reminderTask, DateTime triggerTime, string userInputTimeZoneOffset)
{
    try
    {
        // 标准化触发时间，消除毫秒级差异
        var normalizedTime = new DateTime(triggerTime.Year, triggerTime.Month, triggerTime.Day, triggerTime.Hour, triggerTime.Minute, 0);
        
        lock (_timedReminders)
        {
            if (_timedReminders.TryGetValue(normalizedTime, out var existingEntry))
            {
                // 已有对应定时器，直接添加提醒到列表
                existingEntry.Reminders.Add(reminderTask);
                return;
            }

            var delay = normalizedTime - DateTime.Now;
            var newReminders = new List<ReminderListDto> { reminderTask };
            
            var timer = new Timer(async _ =>
            {
                // 遍历该时间下的所有提醒发送
                foreach (var reminder in newReminders)
                {
                    var conversationReference = turnContext.Activity.GetConversationReference();
                    await ((BotAdapter)turnContext.Adapter).ContinueConversationAsync(_botId, conversationReference, async (ctx, cancellationToken) =>
                    {
                        var displayReminder = ReminderList.DisplayReminder(reminder.Time.ToString("HH:mm"), reminder.ReminderType, reminder.Priority, reminder.ReminderDetails);
                        var adaptiveCardAttachment = new Attachment()
                        {
                            ContentType = "application/vnd.microsoft.card.adaptive",
                            Content = JsonConvert.DeserializeObject(displayReminder),
                        };
                        await ctx.SendActivityAsync(MessageFactory.Attachment(adaptiveCardAttachment), cancellationToken);
                    }, default);
                    // 发送后删除SharePoint中的提醒
                    await DeleteReminderFromSharePointAsync(reminder.ReminderId);
                }

                // 触发完成后移除全局字典中的对应条目
                lock (_timedReminders)
                {
                    _timedReminders.Remove(normalizedTime);
                }

            }, null, (int)delay.TotalMilliseconds, Timeout.Infinite);

            _timedReminders.Add(normalizedTime, (newReminders, timer));
        }
    }
    catch (Exception ex)
    {
        _logger.LogInformation($"error at setting reminder timer: {ex.Message}");
        throw;
    }
}

方案二：通过SharePoint标记提醒发送状态 #

在SharePoint的提醒表中新增IsSent布尔字段（默认值false），发送前先标记状态，确保每个提醒仅发送一次：

// 修改定时器回调中的逻辑
var reminders = await _sharePointLogger.GetReminderFromSharePointAsync(reminderTask, userInputTimeZoneOffset);
foreach (var reminder in reminders.Where(r => !r.IsSent && DateTime.Now > r.Time))
{
    // 先将提醒标记为已发送（需确保SharePoint操作的原子性，避免并发问题）
    await _sharePointLogger.MarkReminderAsSentAsync(reminder.ReminderId);
    
    // 再发送自适应卡片
    var conversationReference = turnContext.Activity.GetConversationReference();
    await ((BotAdapter)turnContext.Adapter).ContinueConversationAsync(_botId, conversationReference, async (turnContext, cancellationToken) =>
    {
        var displayReminder = ReminderList.DisplayReminder(reminder.Time.ToString("HH:mm"), reminder.ReminderType, reminder.Priority, reminder.ReminderDetails);
        var adaptiveCardAttachment = new Attachment()
        {
            ContentType = "application/vnd.microsoft.card.adaptive",
            Content = JsonConvert.DeserializeObject(displayReminder),
        };
        await turnContext.SendActivityAsync(MessageFactory.Attachment(adaptiveCardAttachment), cancellationToken);
    }, default);
}

方案三：清理重复定时器（应急方案） #

若暂时无法重构定时器管理逻辑，可在创建新定时器前，取消同一时间的旧定时器（不推荐长期使用，建议采用方案一或二）：

• 维护全局定时器列表，创建新定时器时遍历列表，取消所有相同触发时间的旧定时器，再创建新的。

内容的提问来源于stack exchange，提问作者Abhay Gupta