Why sort order in table makes the View in initial stage in my MVC application

I want to implement SortOrder into my project. There are few issues at this moment

SortOrder

If I click on th to sort the item, A-Z does not change in the first place but item gets sorted. To make Z-A, I again has to click on th and again it sorts the item.

th

A-Z

Z-A

th

Based on country USA, its data has populated in table when page first loads. But the problem is when I change country to UK or some other countries. I gets the data from database on these search.

USA

UK

Now, I again want to sort th but it reloads the whole page and the page goes into initial stage where Country dropdown changes from UK to USA.

th

UK

USA

Please guide me. I do not know where I am going wrong. Thank you in advance for your kind help!

Model

public class CountryList
{
public int? Country { get; set; }
public IEnumerable<SelectListItem> CountriesList { get; set; }
public IEnumerable<CountryClass> Lists { get; set; }

}
public class CountryClass
{
public string NameInfo { get; set; }
public string AddressInfo { get; set; }

//Filter DropdownList
[Display(Name = "Country")]
public int? Country { get; set; }

}


Controller

[HttpGet]
public ActionResult CountrySearch(int? country, string sortOrder, string currentFilter)
{
CountryList cls = new CountryList();
CountryData db = new CountryData();
IEnumerable<CountryClass> data;

ViewBag.CurrentSort = sortOrder;
ViewBag.NameSortParam = sortOrder == "Name" ? "name_desc" : "Name";
ViewBag.breedingSortParam = sortOrder == "Address" ? "address_desc" : "Address";

if (country != null)
{
data = db.CountryFilter(country.Value);
}
else
{
cls.Country = "USA";
data = db.CountryFilter(country.Value);
}

switch (sortOrder)
{

case "Name":
data = data.OrderBy(s => s.NameInfo);
break;
case "name_desc":
data = data.OrderByDescending(s => s.NameInfo);
break;
case "Address":
data = data.OrderBy(s => s.AddressInfo);
break;
case "address_desc":
data = data.OrderByDescending(s => s.AddressInfo);
break;
default:
data = data.OrderBy(s => s.NameInfo);
break;
}

CountryList model = new CountryList
{

CountriesList = new List<SelectListItem>
{

new SelectListItem { Value = "1", Text = "Nepal" },
new SelectListItem {Value = "120", Text = "India" },
new SelectListItem {Value = "121", Text = "USA" },
new SelectListItem { Value = "134", Text = "Australia" },
new SelectListItem { Value = "137", Text = "UK" },
},
Lists = data
};
return View(model);
}


View

@using (Html.BeginForm("CountrySearch", "CountrySearch", FormMethod.Get))
{