Post Request not receiving any Data

I am trying to make a PostRequest from Unity that creates a new account in a database. When I run the Post Request function(click the submit button), a new Account is created in the database but all of the values are null. I am unable to get any of the data at the controller. I am sending the data as a string in Json format. Any help is appreciated.

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.

Sending large amount of data from view to controller in asp.net

To be more specific let me explain what did I encounter.
I was trying to submit a List of data from view to controller. I was able to submit some data successfully without any problem. But the problem arises when the data is more than around a list of 250 items and more than that. When I click a submit button it passes a NULL value when I debug it. There is no error with my code because I have submitted a list of 100 items to the controller without any problem. I guess there will be something that I have to specify so that It will also send a large number of lists.
Here I’m not using ajax or any javascript code to submit the form. I’m submitting it directly to the controller using post request.