覆盖派生类中的 NotMapped 属性

Question

I'm working on an EF Code-First based application. I have a base class inherited by dozens of classes, each representing entities in database. The base class has a property with [NotMapped] attribute, that was originally required to be [NotMapped] for all derived classes as well.

public class BaseEntity
{
    [NotMapped]
    public string Message { get; set; }
}

I've come across an entity having column name exactly as that property name, but just due to inheriting [NotMapped] attribute from the parent, the value doesn't get stored in database.

public class InheritedEntity : BaseEntity
{
    public string Message { get; set; } // This is what I want mapped
}

Is there any way to override the NotMapped behaviour just for that class, either through DataAnnotations or FluentAPI? I've tried setting [Column()] but it doesn't work.

Answer 1

You need to create a new attribute that does what NotMapped do.

NotMappedPropertyAttributeConvention

Applies the ff to your modelBuilder configuration:

public class CustomNotMappedAttribute : Attribute
{
    public CustomNotMappedAttribute()
    {
        this.Ignore = true;
    }
    public bool Ignore { get; set; }
}

First, create custom attribute.

public class CustomNotMappedPropertyAttributeConvention : PropertyAttributeConfigurationConvention
{
    public override void Apply(PropertyInfo memberInfo, ConventionTypeConfiguration configuration, CustomNotMappedAttribute attribute)
    {
        if (attribute.Ignore)
        {
            configuration.Ignore(memberInfo);
        }
    }
}

Then, create a PropertyAttributeConvention

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Conventions.Add(new CustomNotMappedPropertyAttributeConvention());
}

Then, add it to the configuration conventions

[CustomNotMapped]

Your property in entitybase should be decorated with:

public class BaseEntity
{
    [CustomNotMapped]
    public virtual string Message { get; set; }
}

public class InheritedEntity : BaseEntity
{
    [CustomNotMapped(Ignore = false)]
    public override string Message { get; set; }
}

instead of

[NotMapped]

 public class BaseEntity { [CustomNotMapped] public virtual string Message { get; set; } } public class InheritedEntity : BaseEntity { [CustomNotMapped(Ignore = false)] public override string Message { get; set; } }

There you go. Your message property in your BaseEntity will be ignore except to those decorated with [CustomNotMapped(Ignore = false)]