How can I do this for DropDownList in MVC5?

Question

Hello to All,

I have three dropdownlists.
1.Organisation
2.Department
3.Grades


I want that when I select an organisation at that time department and grade drop down list should be populated, if I select 2nd organisation depend on that organisation department and grade drop down should be changed?

Every organisation has their department and grades. 

Can any one give me the suggestion with demo code?

I know how to do it with json result method for cascading only one drop down list.

Thanks