如何在不知道更新了哪些字段的情况下处理更新实体?

I have a view in my MVC app which has some (but not all) properties of my entity exposed for editing. There are other entity properties which are not exposed to the user. Right now, the form is posted to my controller in the form of a parameter of my entity type. The entity has valid values for the fields exposed in the view, but the rest of the unexposed fields are null. If I go to my repository and try to update the existing entity with this one, many fields will be overwritten with null values.I have a view in my MVC app which has some (but