针对Azure表服务的LINQ查询失败

Question

I have a few records saved in my Azure Table Storage. I'm trying to pull records from a table,for only a particular day/date, for the currently logged in user.

My query returns nothing, so my list is always empty, even though I know that I have 3 records for this month, in my table.

I'm not sure why the query fails in this case. How do I pull records for a specific date, for a specific user? Any help?

This is what I've tried so far:

 public async Task<Result<List<Alert>>> FetchAlertsForDate (DateTime date)
    {

  try {

       var fromDate = new DateTime(date.Year,date.Month,date.Day,0,0,0); //lets create a 12:00:00 AM date

       var toDate = new DateTime(date.Year,date.Month,date.Day,23,59,59); //lets create a 23:59:59PM date

       var alertTable=client.GetSyncTable<Alert>();

       var alerts = await alertTable.Where(n=>n.AccountId==client.CurrentUser.UserId).Where(n=> n.StartDate >= fromDate && n.StartDate <= toDate).ToListAsync();

       return Result<List<Alert>>.Success(alerts);


  } catch (Exception ex) {
            return Result<List<Alert>>.Failure (ex.Message + ex.StackTrace);    
        }

   }

Answer 1

The code you have written contains no obvious bugs to answer your question

How do I pull records for a specific date, for a specific user?

Rather than a date range you use in your method you can just compare the date part of a dateTime like this;

   var alerts = await alertTable.Where(n=>n.AccountId==client.CurrentUser.UserId).Where(n=> n.StartDate.Date == date.Date).ToListAsync();

I think you can do away with the second where clause too;

   var alerts = await alertTable.Where(n=>n.AccountId==client.CurrentUser.UserId && n.StartDate.Date == date.Date).ToListAsync();

If you are not getting any records then for that specific combination of userId and Date then the most likely thing is that there aren't any records with that exact combination.

Answer 2

For some reason, the same query ended up working. I improved on it by removing the first part, where I was checking for the current user's id. That wasn't necessary since in my case.

So the final query looks like this:

   var alerts = await alertTable.Where(n=> n.StartDate >= fromDate && n.StartDate <= toDate).ToListAsync();

This now pulls up all the logged in user's details.