Question

I’ve got a custom attribute BacksCache that I’m using to mark fields in a class that need to be “defaulted” when certain conditions are met.

I’m using the following code:

Type type = obj.GetType();
FieldInfo[] fields = type.GetFields(BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.FlattenHierarchy);

foreach (FieldInfo field in fields)
{
  foreach (Attribute at in field.GetCustomAttributes(true))
  if (at is BacksCache)
  {
    field.SetValue(obj, Utils.DefaultValue(field.FieldType));
  }
}

This code works fine, provided that the class inheritance hierarchy is flat. That is to say, if type is the Type that declares all the attributed fields, everything’s great. As soon as I have a class A from which descends class B (B : A) and B has some attributed fields things fall apart: only the fields declared by A are detected and “defaulted”.

The fields in question are private or private volatile, if that makes any difference.

Any ideas on how to fix this?

Answer 1

Beware of the small print for the BindingFlags.FlattenHierarchy option:

Specifies that public and protected
static members up the hierarchy should
be returned. Private static members
in inherited classes are not
returned. Static members include
fields, methods, events, and
properties. Nested types are not
returned.

The “static” word in the bolded phrase is an oops, no private members are returned. To work around this you’ll need to move up the inheritance chain through Type.BaseType.