EF Core-自动设置字段值

Question

I'm developing a web app using ASP.NET Core + Entity Framework Core .

I'd like to store more info regarding creation , modification & deletion .

My EF entities implement interfaces which bring the following fields:

• DateTime CreationTime { get; set; }
• long? CreatorUserId { get; set; }
• DateTime? ModificationTime { get; set; }
• long? ModifierUserId { get; set; }
• DateTime? DeletionTime { get; set; }
• public long? DeleterUserId { get; set; }
• bool IsDeleted { get; set; }
• int TenantId { get; set; }

I've been trying to make my app set all of the fields automatically .

Right now I am only able to handle the DateTime fields:

AppDbContext.cs

public override async Task<int> SaveChangesAsync(CancellationToken cancellationToken = default(CancellationToken))
{
    ChangeTracker.DetectChanges();
    ChangeTracker.ProcessModifiedTime();
    ChangeTracker.ProcessSoftDelete();
    ChangeTracker.ProcessCreationTime();

    return (await base.SaveChangesAsync(true, cancellationToken));
}

ChangeTrackerExtensions.cs

public static class ChangeTrackerExtensions
{
    public static void ProcessCreationTime(this ChangeTracker changeTracker)
    {
        foreach (var item in changeTracker.Entries<ICreationTime>().Where(e => e.State == EntityState.Added))
        {
            item.CurrentValues[AppConsts.CreationTime] = DateTime.Now;
        }
    }

    public static void ProcessModifiedTime(this ChangeTracker changeTracker)
    {
        foreach (var item in changeTracker.Entries<IModificationTime>().Where(e => e.State == EntityState.Modified))
        {
            item.CurrentValues[AppConsts.ModificationTime] = DateTime.Now;
        }
    }

    public static void ProcessSoftDelete(this ChangeTracker changeTracker)
    {
        foreach (var item in changeTracker.Entries<ISoftDelete>().Where(e => e.State == EntityState.Deleted))
        {
            item.State = EntityState.Modified;
            item.CurrentValues[AppConsts.IsDeleted] = true;
            item.CurrentValues[AppConsts.DeletionTime] = DateTime.Now;
        }
    }
}

---

At a Service Layer or Controller level it is possible to assign the required value each time ( CreatorUserId , MofidierUserId , DeleterUserId ) but this becomes a routine task, very tedious .

I've seen the AspNetBoilerplate implementation , but what worries me about it is that the developers make their DbContext dependent on Session and other stuff.

public abstract class AbpDbContext : DbContext, ITransientDependency, IShouldInitialize
{ 
    public IAbpSession AbpSession { get; set; }
    public IEntityChangeEventHelper EntityChangeEventHelper { get; set; }
    public ILogger Logger { get; set; }
    public IEventBus EventBus { get; set; }
    public IGuidGenerator GuidGenerator { get; set; }
    public ICurrentUnitOfWorkProvider CurrentUnitOfWorkProvider { get; set; }
    public IMultiTenancyConfig MultiTenancyConfig { get; set; }
    ...

IMHO, this is a typical violation of Single Responsibility Principle .

I tried looking into interceptors , but they seem to be available only in ordinary (non-core) edition of Entity Framework - still haven't managed to get my head around how to implement what I mentioned above.

Really, I'm completely lost as to how to handle it with Entity Framework Core. Can anyone think of any Service Layer level solution for that? Or maybe there's a better way?

Answer 1

UserId and TenantId here are just pieces of data that your repository service (here a DbContext) needs. If a service needs data, it should be injected into the service.

Without DI you might make UserID and TenantID constructor parameters on your DbContext. With DI you might inject a dependency on a service that provides this data.