DataTable server side processing not working in .net 2.0

I have a JQuery Datatable (server side processing) working in .Net 4.5 but the same code is not working in .Net 2.0.

Due to specific requirements, i need to implement this in net 2.0 .

I get the following Internal Server Error 500 error message;

enter image description here

Here is the code to initialise DataTable

     $('#tblDetails').DataTable({
        "processing": true,
        "serverSide": true,
        "pageLength": 400,
        "bDestroy": true,
        "scrollY": "300px",
        "scrollCollapse": true,
        
        "ajax": {

            url: "Service.asmx/GetDataForDataTable", type: "post",
            data: function (d) {
                d.regDate = registration_date,
                d.Salary = salary;
            }
        },
        "columns": [
                 { "data": "Name" },
                 { "data": "Date" },

        ]

    });

Here is the DataTable response call;

public class DataTableResponse
{
 public int draw;
 public int recordsTotal;
 public int recordsFiltered;
 public List<SampleDetails> data;
}

If i pass the parameters in the following format then there is no error but server side method is not being called and datatable is stuck on processing.

data: "{ regDate: '" + registration_date + "', Salary: '" + salary + "'}",