DemoCode

DemoCode.cs

var instances = await context.Instances
    .Where(i =>
        i.SubjectUuid == subjectUuid &&
        i.VersionUuid == versionUuid)
    .Select(i => new
    {
        Instance = i,
        HasSubmissions = i.Submissions.Any() // using Any() to check if any submissions are there or not 
    })
    .AsSplitQuery()
    .ToListAsync();

foreach (var item in instances)
{
    UpdateInstancesWithEndDate(
        item.Instance,
        item.HasSubmissions
    );
}