LINQ to SQL query not returning correct DateTime

Question

I am trying to pull the most recent DateTime field from SQLite and it is returning the incorrect time.

Here's data in the database:

And here is my method to get the most recent DateTime via LINQ:

    public string getLastSyncTime()
    {
        using (var db = new SQLite.SQLiteConnection(this.DBPath))
        {
            var query = db.Table<SyncAudit>()
                       .OrderByDescending(c => c.SyncTime)
                       .Select(c => c.SyncTime)
                       .FirstOrDefault();

          return query.ToString();
        }
    }

The issue is that it is not returning the expected datetime. I am getting 1/1/0001 12am:

What am I doing wrong?

EDIT: THis is the provider being used, per request: https://components.xamarin.com/view/sqlite-net

Edit 2: Requested SyncAudit Class:

class SyncAudit
{
    public string Server { get; set; }
    public string Database { get; set; }
    public DateTime SyncTime { get; set; }
    public int Successful { get; set; }
}

Answer 1

Change

public DateTime synctime{ get; set; }

to:

public DateTime? synctime { get; set; }

Hope it will helps. What happens is DateTime is NOT NULL data type and it enforces to put a default value there (01/01/0001) to make sure that non-null date will be submitted.Don't know whether it can be an issue..try and check

Answer 2

I looked at all possible scenarios when this result can happen. There is only one logical explanation to your problem. Your

db.Table<SyncAudit>()

is an empty collection and when you select

db.Table<SyncAudit>()
                   .OrderByDescending(c => c.SyncTime)
                   .Select(c => c.SyncTime)
                   .FirstOrDefault();

it will naturally return you default value of the DateTime. Check your database connection and make sure it works first.

Answer 3

To diagnose what the problem is, go back to basics. Change the LINQ into a foreach loop to iterate over all the records, and find the biggest value. Now step through the code (because I suspect that won't do what you expect either) and you'll see what's going wrong. Then tell us what was wrong.

Answer 4

I often have this issue using Select with SQLite . I don't know where the problem actually is, but it seems like lazy loading is broken so you end up getting default values when it comes time to evaluate the query. I solve this by forcing evaluation before the Select . It's annoying but it works:

Broken example (my own):

        using (var db = new SQLiteConnectionWithLock(base.DatabasePath))
        {
            return db.Table<VideoUploadChunk>()
                .Where(c => c.VideoId == videoId)
                .Select(c => c.ChunkNumber)
                .ToList();
        }

This should return a list of ints , but it ends up returning a bunch of 0's (the default).

Fixed example:

        using (var db = new SQLiteConnectionWithLock(base.DatabasePath))
        {
            var result = db.Table<VideoUploadChunk>()
                .Where(c => c.VideoId == videoId)
                .ToList();

            return result.Select(c => c.ChunkNumber);
        }

Your example (hopefully fixed):

    using (var db = new SQLite.SQLiteConnection(this.DBPath))
    {
        var query = db.Table<SyncAudit>()
                   .OrderByDescending(c => c.SyncTime)
                   .FirstOrDefault();

        return query.Select(c => c.SyncTime).ToString();
    }

Answer 5

SQLite don't have special type for date and time , instead it use either number or text to store such data. SQLiteConnection constructor has a parameter storeDateTimeAsTicks which tell your provider how it should interpet and store date and time values. It is true by default.

So maybe SyncTime is stored in your database as a text rather than a number. Try to adjust connection so provider can interpret data correctly by passing false as storeDateTimeAsTicks :

var db = new SQLite.SQLiteConnection(this.DBPath, storeDateTimeAsTicks: false)