Business Validation Logic Code Smell

Question

Consider the following code:

partial class OurBusinessObject {
    partial void OnOurPropertyChanged() {
        if(ValidateOurProperty(this.OurProperty) ==          


        

Answer 1

To me this looks like the symptom, rather than the actual problem. What's really going on is that the setter for OurProperty fails to preserve the original value for use in the OnOurPropertyChanged event. If you do that, suddenly it becomes easier to make better choices about how to proceed.

For that matter, what you really want is an OnOurPropertyChanging event that is raised from the setter before the assignment actually takes place. This way you can allow or deny the assignment in the first place. Otherwise there is a small amount of time where your object is not valid, and that means the type is not thread safe and you can't count on consistency if you you consider concurrency is a concern.