Knockout Validation Groups

To only validation certain properties in your Knockout ViewModel, you'll need to set up Validation Groups (it's a similar concept to ASP.NET WebForms ValidationGroups). The accepted answer in this StackOverflow post shows a clean and clear way of doing this:

http://stackoverflow.com/questions/13037713/how-to-use-ko-validation-group-function

tl;dr: Group each property in a proxy object and validate each proxy object instead of the entire ViewModel.