Asp.Net Core - The configured user limit (128) on the number of inotify instances has been reached

the asp.net core MVC report error after certain times of query to the mysql database (on Ubuntu 14.04/16.04) with the following message:"The configured user limit (128) on the number of inotify instances has been reached."It can be identified that the error was raised because of the controller opened too many files and exceeded the limits of iNotify setting (in the /proc/sys/fs/inotify/max_user_instances). But I was just baffled when the ASP.NET opened files on each http request and why it doesn't close the file properly? Any one encounted this issue too?Remarks: I was using Mysql.data.core and mysql.data.entityframeworkcore provider.

    private static string classiferstring = "sports,outdoor,startup,pets,child,adult,elderly";    [AllowAnonymous]    [HttpGet]    public async Task<object> Classify([FromQuery] string classifyword)    {        string[] classifers = classiferstring.Split(',');        if (!classifers.Contains(classifyword))        {            return new            {                status = 0,                info = "WrongClassifier",                Data = ""            };        }        try        {            var predata = await (from d in _context.descriptor                              join a in _context.combination on d.ID equals a.ID                              select new ProductsVM                              {                                  CREATETIME = a.CREATETIME,                                  ID = a.ID,                                  COMPANY = a.COMPANY,                                  NAME = a.NAME,                                  PRICE = a.PRICE,                                  TYPE = a.TYPE,                                  HEADPHOTO = a.HEADPHOTO,                                  REMARK = a.REMARK,                                  Tags = d.Tags,                                  Classifier = d.Classifier,                                  OriginName = d.OriginName,                                  Briefing = d.Briefing                              }).ToListAsync();            var data = (from x in predata                          where x.Classifier.Contains(classifyword.ToLower())                          select x).ToList();            if(predata.Count<=0)            {                return new                {                    status = 2,                    info = "NoResult",                    Data = ""                };            }else            {                return new                {                    status = 1,                    info = "Success",                    Data = data                };            };        }        catch(Exception e)        {            return new            {                status = 0,                info = "Error",                Data = e.Message            };        }    }

Please notice the exception was raised only in the try/catch code block instead of immediately after the action is invokded.

Many thanks if anyone has some clue to resolve this problem.