实体框架在插入子项后不保存导航属性

Question

I have two related entities, an incident and a reports (One to Many). The incident will always be added first. The reports will be added after the incident has been added, but never at the same time. The report change tracking entity shows correct navigational relations after insertion. But when I load the report or incident again, there is no relationship stored.

Any idea what I am doing wrong or missing?

The incident model class (shortened):

public class Incident
{         
    public int Id { get; private set; }              
    public byte[] RowVersion { get; private set; }        
    public string UniqueId { get; set; }
    public ICollection<Report> Reports { get; private set; } = new HashSet<Report>();         
}

The report model class (shortened):

public class Report
{ 
    public int Id { get; private set; }              
    public byte[] RowVersion { get; private set; }         
    public Incident Incident { get; set; }
    public string UniqueId { get; set; }
}

The incident configuration:

internal class IncidentConfiguration : IEntityTypeConfiguration<Incident>
{
    internal static IncidentConfiguration Create() => new IncidentConfiguration();
    public void Configure(EntityTypeBuilder<Incident> builder)
    {
        builder
            .Property(incident => incident.Id)
            .ValueGeneratedOnAdd();
        builder
            .Property(incident => incident.RowVersion)
            .IsConcurrencyToken();
    }
}

The report configuration:

internal class ReportConfiguration : IEntityTypeConfiguration<Report>
{
    internal static ReportConfiguration Create() => new ReportConfiguration();
    public void Configure(EntityTypeBuilder<Report> builder)
    {
        builder
            .Property(report => report.Id)
            .ValueGeneratedOnAdd();
        builder
            .Property(report => report.RowVersion)
            .IsConcurrencyToken();            
        builder
            .HasOne(report => report.Incident)
            .WithMany(incident => incident.Reports)
            .HasForeignKey(report => report.UniqueId)
            .HasPrincipalKey(incident => incident.UniqueId)
            .OnDelete(DeleteBehavior.Cascade);
    }
}

The method to add an incident:

public async ValueTask<EntityEntry<Common.Models.Incident>> AddAsync(Common.Models.Incident incident)
    {
        EntityEntry<Common.Models.Incident> entity = null;
        _manualResetEvent.WaitOne();
        try
        {
            using var context = new IncidentManagerContext(_connectionString);
            entity = await context.Incidents.AddAsync(incident);
            await context.SaveChangesAsync();
        }
        catch (Exception) { entity = null; }
        finally { _manualResetEvent.Set(); }
        return entity;
    }

The method to add a report:

public async ValueTask<EntityEntry<Common.Models.Report>> AddAsync(Common.Models.Report report)
    {
        EntityEntry<Common.Models.Report> entity = null;
        if (!string.IsNullOrEmpty(report.UniqueId))
        {
            _manualResetEvent.WaitOne();
            try
            {
                using var context = new IncidentManagerContext(_connectionString);
                entity = await context.AddAsync(report);
                await context.SaveChangesAsync();
            }
            catch (Exception) { entity = null; }
            finally { _manualResetEvent.Set(); }
        }
        return entity;
    }

Answer 1

Finally I found the issue, it wasn't that async stuff, neither the missing manual assignmet. It were simply the missing extension methods Include and ThenInclude on the loading side...

public async Task<Common.Models.Incident> GetByUniqueIdAsync(string uniqueId)
    {
        Common.Models.Incident incident = null;
        _manualResetEvent.WaitOne();
        try
        {
            using var context = new IncidentManagerContext(_connectionString);
            incident = await context.Incidents
                .Include(incident => incident.Reports)
                .ThenInclude(reports => reports.DetailReports)
                .Where(i => i.UniqueId == uniqueId)
                .SingleAsync();
        }
        catch (Exception) { }
        finally { _manualResetEvent.Set(); }
        return incident;
    }