Question

Consider two .net dlls. The first, “application.dll” contains the main business logic and data access code. The second, “webservice.dll” consists mostly of WebMethods that link to objects and methods with application.dll for the purpose of providing webservice calls to existing code.

What changes (e.g. add new classes, add a new field or method to an existing class etc) can and can’t be made to application.dll without requiring a recompile of webservice.dll?

Answer 1

Most things will be fine; some things that will break it:

• Removing* types that are used (unless you are using type-forwarding)
• Removing* methods that are used (including constructor)
• Changing the signature of methods (that are used)
• Changing public fields to properties (that are used)
• Changing serialization internals if serialization is used
• Adding a method to an interface, where the second dll has a type that implements that interface
• Adding an abstract method to a base-class that is inherited in the second dll
• Almost anything internal if hacky reflection is (ab)used
• Adding constraints to a generic type/method
• Marking a type as sealed when it was inherited in the second dll
• Adding a field to a struct if the caller uses memberwise initialization rather than constructor initialization

(removing includes changing the accessibility to something non-public)