perform a function if the database returns a value automatically asp.net & vb.net application

I want to send user the reminder email automatically without any trigger if a table returns a value on that specific date.

how to do that?

This my code which determines if there is any task on the calendar or not

<WebMethod()> _
<Script.Services.ScriptMethod(ResponseFormat:=Script.Services.ResponseFormat.Json)> _
Public Function UpcomingTasks() As String
    Return GetJson(DB.GetData("select created, title, description, alerttype, convert(varchar, alerttime, 100) alerttime from reminder where alertfor = @uid and convert(date, alerttime) = CONVERT (date, GETDATE()) and deleted = 0 and dismissed = 0 order by alerttime", DB.SIP("uid", LocalHelper.UserID())))
End Function

if there is any task for each task i want to send separate reminder email

this is my code for sending reminder email

Public Sub SendCalender(reminder As Reminder)
    Dim calFile As String
    ' create file name, e.g. [Reminder]-[reminderId]-[createdbyid].ics
    calFile = String.Format("{0}-{1}-{2}.ics", "Reminder", reminder.Id, reminder.CreatedBy)

    ' Create a blank file ready for writing
    Dim w As System.IO.StreamWriter = System.IO.File.CreateText(HttpContext.Current.Server.MapPath("~/uploads/cal/" & calFile))

    w.Write(GenerateCalFile(reminder))

    w.Close()

    Dim _email As New Email()

    With _email

        ' send out invitations
        Dim sTo As String = New User(reminder.AlertFor).Email
        Dim sCC As String = New User(reminder.CreatedBy).Email

        .MailTo = sTo
        .MailCC = sCC
        .MailFrom = sCC

        .Subject = String.Format("{0} on {1}", reminder.Title, reminder.AlertTime.ToString())

        .Attachments = HttpContext.Current.Server.MapPath("~/uploads/cal/" & calFile)

        .Body = reminder.Description

        .Send()
    End With

End Sub

how shall i compare the value and call the send email function