Dynamic linking supports flexible code deployment: partially linked code links further code on the fly, as needed; and thus, end-users receive updates automatically. On the down side, each program run may link different versions of the same code, a powerful feature possibly causing subtle errors which mystify end-users.

Dynamic linking in Java and C# are similar: the same linking phases are involved, soundness is based on similar ideas, and executions which do not throw linking errors of programs in the intersection of the languages give the same result. They are, however, not identical: the linking phases in Java and C# are combined differently, and take place in a different order. Thus, linking errors may be detected at different times in Java and C#.

We develop a non-deterministic model, which includes the behaviour of Java and C#. The non-determinism allows us to describe the design space, to distill the similarities between the two languages, and to use one proof of soundness for both. We prove soundness by means of a subject reduction theorem, and also prove that all execution strategies are equivalent in the sense that all terminating executions which do not involve a link error, give the same result.