Global Filter based on Interface

Question

Is it possible to write the below in one line?

//Create a Global Filter for the TenantId property.
modelBuilder.Entity<Item>().HasQueryFilter(b => EF.Property<int>(b, "TenantId") == this._appUserProvider.CurrentTenantId);
modelBuilder.Entity<Invite>().HasQueryFilter(b => EF.Property<int>(b, "TenantId") == this._appUserProvider.CurrentTenantId);

I have tried an Interface for Item and Invite, but EF threw an error saying it must be a reference type.

I also tried a base class, but I don't want to change the base tables which seemed to be required to make that work.

Any other options?

Answer 1

Let say your entities implement the following interface:

public interface ITenantEntity
{
    int TenantId { get; set; }
}

The most important thing when using common code to configure multiple entities via fluent API is to use the real entity type when calling modelBuilder.Entity<TEntity>(). Using a base class will introduce EF inheritance, and interface will simply generate exception.

The easiest solution IMO is to put the common code in a generic method and call it via reflection.

Start by creating a constrained generic instance method in your derived DbContext class containing the desired fluent configuration:

void ConfigureTenantFilter<TEntity>(ModelBuilder modelBuilder)
    where TEntity : class, ITenantEntity
{
    modelBuilder.Entity<TEntity>()
        .HasQueryFilter(e => e.TenantId == this._appUserProvider.CurrentTenantId);
}

Then use the following snippet at the end of your OnModelCreating override (after all entity types are discovered):

var configureTenantMethod = GetType().GetTypeInfo().DeclaredMethods.Single(m => m.Name == nameof(ConfigureTenantFilter));
var args = new object[] { modelBuilder };
var tenantEntityTypes = modelBuilder.Model.GetEntityTypes()
    .Where(t => typeof(ITenantEntity).IsAssignableFrom(t.ClrType));
foreach (var entityType in tenantEntityTypes)
    configureTenantMethod.MakeGenericMethod(entityType.ClrType).Invoke(this, args);