Custom Conventions — EF Core 7+

IModelFinalizingConvention — Tüm String'lere MaxLength

public class MaxStringLengthConvention : IModelFinalizingConvention
{
    private readonly int _maxLength;

    public MaxStringLengthConvention(int maxLength = 256)
    {
        _maxLength = maxLength;
    }

    public void ProcessModelFinalizing(
        IConventionModelBuilder modelBuilder,
        IConventionContext<IConventionModelBuilder> context)
    {
        foreach (var entity in modelBuilder.Metadata.GetEntityTypes())
        {
            foreach (var property in entity.GetProperties()
                .Where(p => p.ClrType == typeof(string)))
            {
                // Sadece açıkça MaxLength belirtilmemiş olanları ayarla
                if (!property.GetMaxLength().HasValue)
                {
                    property.Builder.HasMaxLength(_maxLength);
                }
            }
        }
    }
}

Convention ile Otomatik Soft Delete Filter

public class SoftDeleteConvention : IModelFinalizingConvention
{
    public void ProcessModelFinalizing(
        IConventionModelBuilder modelBuilder,
        IConventionContext<IConventionModelBuilder> context)
    {
        foreach (var entity in modelBuilder.Metadata.GetEntityTypes())
        {
            var isDeletedProperty = entity.FindProperty("IsDeleted");
            if (isDeletedProperty is not null && isDeletedProperty.ClrType == typeof(bool))
            {
                var parameter = Expression.Parameter(entity.ClrType, "e");
                var prop = Expression.Property(parameter, "IsDeleted");
                var condition = Expression.Equal(prop, Expression.Constant(false));
                var lambda = Expression.Lambda(condition, parameter);

                entity.SetQueryFilter(lambda);
            }
        }
    }
}

Convention ile Otomatik Index (FK'lara)

public class ForeignKeyIndexConvention : IModelFinalizingConvention
{
    public void ProcessModelFinalizing(
        IConventionModelBuilder modelBuilder,
        IConventionContext<IConventionModelBuilder> context)
    {
        foreach (var entity in modelBuilder.Metadata.GetEntityTypes())
        {
            foreach (var fk in entity.GetForeignKeys())
            {
                // FK property'lerine index oluştur (yoksa)
                var properties = fk.Properties;
                var existingIndex = entity.FindIndex(properties);
                if (existingIndex is null)
                {
                    entity.AddIndex(properties);
                }
            }
        }
    }
}

Kayıt

protected override void ConfigureConventions(ModelConfigurationBuilder configurationBuilder)
{
    // Custom conventions
    configurationBuilder.Conventions.Add(_ => new MaxStringLengthConvention(256));
    configurationBuilder.Conventions.Add(_ => new SoftDeleteConvention());

    // Property type conventions (daha basit)
    configurationBuilder.Properties<string>().HaveMaxLength(256);
    configurationBuilder.Properties<decimal>().HavePrecision(18, 2);
    
    // Tüm DateTime'lar → datetime2
    configurationBuilder.Properties<DateTime>().HaveColumnType("datetime2");
}

ConfigureConventions vs OnModelCreating

ConfigureConventions'da belirlenen kural, IEntityTypeConfiguration'da override edilebilir. Yani önce genel kural yazılır, istisnalar entity config'de belirtilir.