Entity Framework Change Tracking API and reference

问题:

Looking to write generic Audit code on my DbContext subclass.

foreach (var entry in this.ChangeTracker.Entries<MyClass>())
{
    if (entry.State == EntityState.Modified)
    {
        var entityProperties = entry.Entity.GetType().GetProperties();
        foreach (var entityProperty in entityProperties)
        {
            DbMemberEntry propertyEntry = entry.Member(property.Name);
            if (propertyEntry is DbPropertyEntry)
            {
                // IsModified available
            }
            else if (propertyEntry is DbReferenceEntry)
            {
                // IsModified not available
            }
        }
    }
}

1) If I only change a reference property, the entry.State value is "Unchanged".

2) Even if point 1 was set to "Modified", the DbReferenceEntry class doesn't seem to have an IsModified property, nor an original value.

I assume this is possible because EF must be tracking this.

Can anyone help?

Thanks, Ben

回答1:

Yes reference entry (navigation property) does not track changes. It is responsibility of foreign key property (in case of foreign key association) or separate object tracking changes of independent association. In ObjectContext API you can get these objects by ObjectStateManager but it looks like DbContext API doesn't have this available. I asked a question about this on MSDN Forum.