How to determine if all objects are serializable in a given namespace?

Question

Some background: We require all of our DTO objects to be serializable so that they can be stored in session or cached.

As you can imagine, this is extremely annoying

Answer 1

You can't find all possible classes in a namespace - but you can find all classes within a given assembly which have the specified namespace, and check those.

string dtoNamespace = ...;
Assembly assembly = ...;
var badClasses = assembly.GetTypes()
                         .Where(t => t.Namespace == dtoNamespace)
                         .Where(t => t.IsPublic) // You might want this
                         .Where(t => !t.IsDefined(typeof(SerializableAttribute),
                                     false);

Assert that badClasses is empty in whatever way you want :)

EDIT: As mentioned in the comments, the IsSerializable property is kinda handy here :)