BaseEntitySaveChangesInterceptor

Namespace: RA.Utilities.Data.EntityFramework.Interceptors

BaseEntitySaveChangesInterceptor sets audit timestamps immediately before EF Core writes changes to the database. It is a SaveChangesInterceptor that overrides both SavingChanges and SavingChangesAsync.

🎯 Purpose

Audit fields are easy to forget and easy to set inconsistently. The interceptor centralizes the logic: whenever an entity is added, CreatedAt is set to DateTime.UtcNow; whenever an entity is modified, LastModifiedAt is set to DateTime.UtcNow. No repository or business code has to remember.

How it works

1. EF Core calls SavingChanges (sync) or SavingChangesAsync (async).
2. The interceptor enumerates context.ChangeTracker.Entries().
3. For every entry in the Added state, it checks the entity's model metadata for a CreatedAt property and sets it.
4. For every entry in the Modified state, it checks for LastModifiedAt and, when present, sets it.

The check is metadata-based (entry.Metadata.FindProperty(...)), not type-based. Any entity that exposes a property with those names is updated, whether or not it derives from a RA.Utilities entity base class.

foreach (EntityEntry entry in context.ChangeTracker.Entries())
{
    if (entry.State is EntityState.Added && entry.Metadata.FindProperty(CreatedAtProperty) is not null)
    {
        entry.Property(CreatedAtProperty).CurrentValue = DateTime.UtcNow;
    }

    if (entry.State is EntityState.Modified && entry.Metadata.FindProperty(LastModifiedAtProperty) is not null)
    {
        entry.Property(LastModifiedAtProperty).CurrentValue = DateTime.UtcNow;
    }
}

Which entities are affected

Entity base	CreatedAt	LastModifiedAt
CoreEntity<TKey>	❌	❌
BaseEntity<TKey>	✅	❌
WriteEntity<TKey>	✅	✅
AuditableBaseEntity<TKey>	✅	✅ (plus CreatedBy / LastModifiedBy, not set by this interceptor)
SoftDeleteEntity<TKey>	✅	✅ (IsDeleted is not managed by this interceptor)

The interceptor writes DateTime.UtcNow for both properties. It does not use the database clock.

🚀 How to Use

Register the interceptor and attach it to the context's options:

using RA.Utilities.Data.EntityFramework.Interceptors;

builder.Services.AddScoped<BaseEntitySaveChangesInterceptor>();

builder.Services.AddDbContext<DbContext, AppDbContext>((provider, options) =>
    options.UseSqlServer(connectionString)
           .AddInterceptors(provider.GetRequiredService<BaseEntitySaveChangesInterceptor>()));

For a context constructed without DI, attach it directly:

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
    optionsBuilder
        .UseSqlServer(connectionString)
        .AddInterceptors(new BaseEntitySaveChangesInterceptor());
}

⚠️ Behavior and limitations

• Only Added and Modified — Deleted entities keep their timestamps, and Unchanged entities are untouched.

• Exact property names — the properties must be named CreatedAt and LastModifiedAt to be detected.

• Timestamps only — CreatedBy and LastModifiedBy are not populated; read the current user and set them in your command handler or a separate interceptor.

• Soft delete is not applied — SoftDeleteEntity<TKey>.IsDeleted is not queried or filtered automatically. Add a global query filter and set the flag in your own code.

• DateTime, not DateTimeOffset — the properties are DateTime; values are UTC.

• Pooled contexts — if you use AddDbContextPool, the interceptor is stateless, so it can safely be registered as a singleton instead of scoped:

  builder.Services.AddSingleton<BaseEntitySaveChangesInterceptor>();