Bot Emualor "ExceptionMessage": "Object reference not set to an instance of an object.", "exceptionType": "System.NullReferenceException",

Question

I want to store the conversation on the chat bot and am using IActivityLogger for it. The code is as follows :

public class EntityFrameworkActivityLogger : IActivityLogger
{
    Task IActivityLogger.LogAsync(IActivity activity)
    {
        IMessageActivity msg = activity.AsMessageActivity();
        using (BotApplicationSqlData.ConversationDataContext dataContext = new BotApplicationSqlData.ConversationDataContext())
        {
            var newActivity = Mapper.Map<IMessageActivity, BotApplicationSqlData.Activity>(msg);
            if (string.IsNullOrEmpty(newActivity.Id))
                newActivity.Id = Guid.NewGuid().ToString();
            dataContext.Activities.Add(newActivity);
            dataContext.SaveChanges();
        }
        return null;
    }
}

I am getting an error of Request to

'https://botapplicationsqlexample.azurewebsites.net/api/messages' failed: [500] Internal Server Error .

On debugging, it shows a Null Reference Exception and Object reference not set to an instance of an object.

The conversation is getting stored on the Azure DB but no reply from the Bot's end is coming. Can anyone please help with me this?

Answer 1

I ran this code, and noticed that if an activity of type ActivityTypes.Typing comes through, activity.AsMessageActivity() returns a null object. To fix this, just surround the saving code with a null check:

    public async Task LogAsync(IActivity activity)
    {
        IMessageActivity msg = activity.AsMessageActivity();

        if (msg != null)
        {
            using (Data.ConversationDataContext dataContext = new Data.ConversationDataContext())
            {
                var newActivity = Mapper.Map<IMessageActivity, Data.Activity>(msg);
                if (string.IsNullOrEmpty(newActivity.Id))
                    newActivity.Id = Guid.NewGuid().ToString();

                dataContext.Activities.Add(newActivity);
                dataContext.SaveChanges();
            }
        }
    }