if GetFields() doesn't guarantee order, how does LayoutKind.Sequential work

Question

I need to get fieldinfo in a guaranteed order with respect to declaration order. Right now I'm using attributes to specify order.

Is there a more automatic way of doing this?

Does anyone have knowledge of how LayoutKind.Sequential works, and if I can apply its technique.

I don't see how LayoutKind.Sequential works, unless there's some precompiler code that adds attributes.

Answer 1

If you want the ordering of the fields returned by Type.GetFields to be stable, try sorting by the MetadataToken property.

Type myType = ...
BindingFlags flags = ...
IEnumerable<FieldInfo> orderedFields = myType.GetFields(flags)
                                             .OrderBy(field => field.MetadataToken);

Empirically, ordering fields in this manner has been found to return them in declaration order, although this isn't documented.

By the way, the question as asked doesn't entirely make sense; there isn't any reason to believe that the reflection API is tied in any way to how the runtime lays objects out in memory.

Answer 2

The question is old but not so old... I'm dealing now with the same problem. And I prefer to get the fields in tho order of declaration. The following call should work for a value type or a formatted reference type.

var fields = type.GetFields().OrderBy(f => Marshal.OffsetOf(type, f.Name).ToInt32());

Enjoy!