Validation for DropDownLists Broken

This is related to a previous question on passing model data to a partial view from two DropDownLists where the user must select department and year in a view. Numerical data is then displayed in a table in the partial view. The view contains the dropdowns and the table headers. The partial view contains the rows with the numerical data. Right now, the validation is broken. Both dropdowns are required. If I submit form with either dropdown not selected, I get this error:

Should I separate ViewModel for Login and Registration in asp.net?

I have 3 types of user in my application(in asp.net mvc-5): Admin, Doctor and User. In Models folder I’ve created 3 other folder, one for each type of user. Should I create a single ViewModel, suppose DoctorViewModel which will carry all information about doctor? Or should I create DoctorLoginViewModel and DoctorRegistractionViewModel and so on?

Binding DropDownList from Database

I’m building a view which will display tabular data based on selections from two dropdownlists, the first which selects departments is populated from the database. The second is a static dropdownlist for “Year” which I haven’t got to yet. There are answers to similar questions, but I’ve looked at them and tried everything. I’ve got to the point where I’m getting a null exception in the view where I created the markup for the dropdownlist.