In EF Core 2.0, we have the ability to derive from IEntityTypeConfiguration
for cleaner Fluent API mappings (source).
How can I extend this pattern to utili
There is another way to solve the problem, and that is to use Template Method Design Pattern. Like this:
public abstract class BaseEntityTypeConfiguration<TBase> : IEntityTypeConfiguration<TBase>
where TBase : BaseEntity
{
public void Configure(EntityTypeBuilder<TBase> entityTypeBuilder)
{
//Base Configuration
ConfigureOtherProperties(builder);
}
public abstract void ConfigureOtherProperties(EntityTypeBuilder<TEntity> builder);
}
public class MaintainerConfiguration : BaseEntityTypeConfiguration<Maintainer>
{
public override void ConfigureOtherProperties(EntityTypeBuilder<Maintainer> entityTypeBuilder)
{
entityTypeBuilder.Property(b => b.CreatedDateUtc).HasDefaultValueSql("CURRENT_TIMESTAMP");
}
}
With this way you don't need to write any single line in child configuration.
Something like this could work (untested)?
public abstract class BaseEntityTypeConfiguration<TBase> : IEntityTypeConfiguration<TBase>
where TBase : BaseEntity
{
public virtual void Configure(EntityTypeBuilder<TBase> entityTypeBuilder)
{
//Base Configuration
}
}
public class MaintainerConfiguration : BaseEntityTypeConfiguration<Maintainer>
{
public override void Configure(EntityTypeBuilder<Maintainer> entityTypeBuilder)
{
entityTypeBuilder.Property(b => b.CreatedDateUtc).HasDefaultValueSql("CURRENT_TIMESTAMP");
base.Configure(entityTypeBuilder);
}
}
Another approach if you dont want to repeat the column Definitions for all of your Models that inherit from the same base Entity like this:
protected override void OnModelCreating(ModelBuilder modelBuilder){
modelBuilder.Entity<Order>()
.Property(b => b.CreatedDateTime)
.HasDefaultValueSql("CURRENT_TIMESTAMP ");
modelBuilder.Entity<Adress>()
.Property(b => b.CreatedDateTime)
.HasDefaultValueSql("CURRENT_TIMESTAMP ");
// …
}
is to find all the Entites that inhert from the base Entity, loop over them and call the generic Method as shown below, in which the redundant Logic is placed:
protected override void OnModelCreating(ModelBuilder modelBuilder){
foreach (Type type in GetEntityTypes(typeof(BaseEntity))){
var method = SetGlobalQueryMethod.MakeGenericMethod(type);
method.Invoke(this, new object[] { modelBuilder });
}
}
static readonly MethodInfo SetGlobalQueryMethod = typeof(/*your*/Context)
.GetMethods(BindingFlags.Public | BindingFlags.Instance)
.Single(t => t.IsGenericMethod && t.Name == "SetGlobalQuery");
public void SetGlobalQuery<T>(ModelBuilder builder) where T : BaseEntity{
builder.Entity<T>().Property(o => o.CreatedDateTime).HasDefaultValueSql("CURRENT_TIMESTAMP");
// Additional Statements
}
For the "GetEntityTypes" Method you need the Nuget Package „Microsoft.Extensions.DependencyModel“
private static IList<Type> _entityTypeCache;
private static IList<Type> GetEntityTypes(Type type)
{
if (_entityTypeCache != null && _entityTypeCache.First().BaseType == type)
{
return _entityTypeCache.ToList();
}
_entityTypeCache = (from a in GetReferencingAssemblies()
from t in a.DefinedTypes
where t.BaseType == type
select t.AsType()).ToList();
return _entityTypeCache;
}
private static IEnumerable<Assembly> GetReferencingAssemblies()
{
var assemblies = new List<Assembly>();
var dependencies = DependencyContext.Default.RuntimeLibraries;
foreach (var library in dependencies)
{
try
{
var assembly = Assembly.Load(new AssemblyName(library.Name));
assemblies.Add(assembly);
}
catch (FileNotFoundException)
{ }
}
return assemblies;
}
Its a bit hacky in my opinion, but works fine for me!
The source with more details:
https://www.codingame.com/playgrounds/5514/multi-tenant-asp-net-core-4---applying-tenant-rules-to-all-enitites
I'm late to the party, but this is what I did in the OnModelCreating method to achieve similar results.
Basically, I have (4) properties that inherit from a BaseEntity. Two of those are dates why two are strings.
For the dates, I wanted the default to be SQL's GETUTCDATE and the string to be "SystemGenerated." Using a static helper that allows me to retrieve the property name from BaseEntity in a strongly-typed manner, I grab the (4) property names. Then, I iterate over all of the iterate over all of the ModelBuilder entities after my primary mappings are set-up. This allows modelBuilder.Model.GetEntityTypes to return the entities that the modelBuidler is aware of. Then it's a matter of looking at the ClrType.BaseType to see if the type inherits from my BaseEntity and setting the defaults on the PropertyBuilder.
I tested this directly and through EF Migrations which confirmed that the proper SQL was generated.
var createdAtUtc = StaticHelpers.GetPropertyName<BaseEntity>(x => x.CreatedAtUtc);
var lastModifiedAtUtc = StaticHelpers.GetPropertyName<BaseEntity>(x => x.LastModifiedAtUtc);
var createdBy = StaticHelpers.GetPropertyName<BaseEntity>(x => x.CreatedBy);
var lastModifiedBy = StaticHelpers.GetPropertyName<BaseEntity>(x => x.LastModifiedBy);
foreach (var t in modelBuilder.Model.GetEntityTypes())
{
if (t.ClrType.BaseType == typeof(BaseEntity))
{
modelBuilder.Entity(t.ClrType).Property(createdAtUtc).HasDefaultValueSql("GETUTCDATE()");
modelBuilder.Entity(t.ClrType).Property(lastModifiedAtUtc).HasDefaultValueSql("GETUTCDATE()");
modelBuilder.Entity(t.ClrType).Property(createdBy).HasDefaultValueSql("SystemGenerated");
modelBuilder.Entity(t.ClrType).Property(lastModifiedBy).HasDefaultValueSql("SystemGenerated");
}
}
Here is the the static helper for getting property names for a given type..
public static string GetPropertyName<T>(Expression<Func<T, object>> expression)
{
if (expression.Body is MemberExpression)
{
return ((MemberExpression)expression.Body).Member.Name;
}
else
{
var op = ((UnaryExpression)expression.Body).Operand;
return ((MemberExpression)op).Member.Name;
}
}