Any way to make EntityFramework's SaveChanges() method skip an entry if it already exists?

Question

I have a Tag model in my application:

public class Tag
{
    public Tag() { }
    public Tag(string t)
    {
        Name = t;
        Pictures = new List<Picture>();
    }

    public int Id { get; set; }
    [MaxLength(96), Index(IsUnique = true)]
    public string Name { get; set; }

    public virtual List<Picture> Pictures { get; set; }

}

Is there any way to tell the framework to do ON DUPLICATE DO NOTHING, when a record with the same Name already exists? This always throws a Duplicate exception and I'd like it to just ignore it and move on.

Edit: I've changed the EF code across many threads to this:

async Task SaveQueue()
{
    for (;;)
    {
        try
        {
            await Task.Delay(7500);
            dbUploadProgress.Visibility = Visibility.Visible;
            dbUploadProgress.Value = 0;
            var q = new ObservableCollection<Picture>(manager.Queue.ToList().AsEnumerable());
            manager.Queue.Clear();
            var imgcount = q.Count();
            for (int i = 0; i < imgcount; i++)
            {
                using (var pc = new PicsContext())
                {
                    var tags = q[i].GetTags();
                    pc.Sites.Attach(q[i].Site); // I'm actually not sure how to use this. 
                    var curUrl = q[i].Url;
                    if (pc.Pictures.FirstOrDefault(o => o.Url == curUrl) != null)
                        continue;
                    foreach (var t in tags)
                    {
                        var tag = pc.Tags.Where(o => o.Name == t).FirstOrDefault();
                        if (tag == null)
                        {
                            tag = new ViewModel.Tag(t);
                        }
                        q[i].Tags.Add(tag);
                        try
                        {
                            await pc.SaveChangesAsync();
                        }
                        catch { }
                    }
                    pc.Pictures.Add(q[i]);
                    try
                    {
                        await pc.SaveChangesAsync();
                    }
                    catch { }
                    dbUploadProgress.Value = (i + 1) / (double)imgcount;
                }
            }
            q.Clear();
            MainWindow.AddLog(string.Format("Saved {0} pictures.", imgcount));
            dbUploadProgress.Visibility = Visibility.Collapsed;
            await Task.Delay(1500);
        }
        catch { }
        if (isStopped)
            break;
    }
}

The problem still exists, though.

Answer 1

Why don't you ran an dbContext.Get.Any(x=>x.Name==tag.Name) and skip adding the new tag based on it?

I think the problem is that your queue processes messages async, so you can have 2 threads trying to insert same tag because the check if exists logic ran before an insert has been made.

You can fix the problem by processing just 1 queue message at a time (having one worker/thread processing the queue).

Or another work around might be to isolate the tags saving in a try catch and handle the duplicate exception properly (reloading the tag from db and use that one when setting it on the new object).