EF: Validation failing on update when using lazy-loaded, required properties

Question

Given this extremely simple model:

public class MyContext : BaseContext
{
    public DbSet Foos { get; set; }
    public DbSet Bars { g         


        

Answer 1

If anyone wants a general approach to solve this problem, here you have a custom DbContext which finds out properties based on these constraints:

• Lazy Load is ON.
• Properties with virtual
• Properties having any ValidationAttribute attribute.

After retrieving this list, on any SaveChanges in which have something to modify it will load all references and collections automatically avoiding any unexpected exception.

public abstract class ExtendedDbContext : DbContext
{
    public ExtendedDbContext(string nameOrConnectionString)
        : base(nameOrConnectionString)
    {
    }

    public ExtendedDbContext(DbConnection existingConnection, bool contextOwnsConnection)
        : base(existingConnection, contextOwnsConnection)
    {
    }

    public ExtendedDbContext(ObjectContext objectContext, bool dbContextOwnsObjectContext)
        : base(objectContext, dbContextOwnsObjectContext)
    {
    }

    public ExtendedDbContext(string nameOrConnectionString, DbCompiledModel model)
        : base(nameOrConnectionString, model)
    {
    }

    public ExtendedDbContext(DbConnection existingConnection, DbCompiledModel model, bool contextOwnsConnection)
        : base(existingConnection, model, contextOwnsConnection)
    {
    }

    #region Validation + Lazy Loading Hack

    /// 

    /// Enumerator which identifies lazy loading types.
    /// 
    private enum LazyEnum
    {
        COLLECTION,
        REFERENCE,
        PROPERTY,
        COMPLEX_PROPERTY
    }

    /// 

    /// Defines a lazy load property
    /// 
    private class LazyProperty
    {
        public string Name { get; private set; }
        public LazyEnum Type { get; private set; }

        public LazyProperty(string name, LazyEnum type)
        {
            this.Name = name;
            this.Type = type;
        }
    }

    /// 

    /// Concurrenct dictinary which acts as a Cache.
    /// 
    private ConcurrentDictionary> lazyPropertiesByType =
        new ConcurrentDictionary>();

    /// 

    /// Obtiene por la caché y si no lo tuviese lo calcula, cachea y obtiene.
    /// 
    private IList GetLazyProperties(Type entityType)
    {
        return
            lazyPropertiesByType.GetOrAdd(
                entityType,
                innerEntityType =>
                {
                    if (this.Configuration.LazyLoadingEnabled == false)
                        return new List();

                    return
                        innerEntityType
                            .GetProperties(BindingFlags.Public | BindingFlags.Instance)
                            .Where(pi => pi.CanRead)
                            .Where(pi => !(pi.GetIndexParameters().Length > 0))
                            .Where(pi => pi.GetGetMethod().IsVirtual)
                            .Where(pi => pi.GetCustomAttributes().Exists(attr => typeof(ValidationAttribute).IsAssignableFrom(attr.GetType())))
                            .Select(
                                pi =>
                                {
                                    Type propertyType = pi.PropertyType;
                                    if (propertyType.HasGenericInterface(typeof(ICollection<>)))
                                        return new LazyProperty(pi.Name, LazyEnum.COLLECTION);
                                    else if (propertyType.HasGenericInterface(typeof(IEntity<>)))
                                        return new LazyProperty(pi.Name, LazyEnum.REFERENCE);
                                    else
                                        return new LazyProperty(pi.Name, LazyEnum.PROPERTY);
                                }
                            )
                            .ToList();
                }
            );
    }

    #endregion

    #region DbContext

    public override int SaveChanges()
    {
        // Get all Modified entities
        var changedEntries =
            this
                .ChangeTracker
                .Entries()
                .Where(p => p.State == EntityState.Modified);

        foreach (var entry in changedEntries)
        {
            foreach (LazyProperty lazyProperty in GetLazyProperties(ObjectContext.GetObjectType(entry.Entity.GetType())))
            {
                switch (lazyProperty.Type)
                {
                    case LazyEnum.REFERENCE:
                        entry.Reference(lazyProperty.Name).Load();
                        break;
                    case LazyEnum.COLLECTION:
                        entry.Collection(lazyProperty.Name).Load();
                        break;
                }
            }
        }

        return base.SaveChanges();
    }

    #endregion
}

Where IEntity is:

public interface IEntity
{
    T Id { get; set; }
}

These extensions were used in this code:

public static bool HasGenericInterface(this Type input, Type genericType)
{
    return
        input
            .GetInterfaces()
            .Any(x => x.IsGenericType && x.GetGenericTypeDefinition() == genericType);
}

public static bool Exists(this IEnumerable source, Predicate predicate)
{
    foreach (T item in source)
    {
        if (predicate(item))
            return true;
    }

    return false;
} 

Hope it helps,