dynamic query in mvc 5

public ActionResult ifcondi(DirectItem di)

{

string getDirectId = HttpUtility.HtmlEncode(di.Id);

var data1 = (from c in db.RowItems

join a in db.categories on c.CategoryItemId equals a.category_id

join d in db.DirectItems on c.DirectItemId equals d.Id

// here plazma 60 is static ..i have many button plazma 60 ,, plazma 90 ,and so on

where d.ItemName == "plazma 60" //insted of static item wht i have to add to make dynamik query

select new { c, a, d }).GroupBy(x => x.a.category_name).Select(y => new tempdata

{

CatagoryName = y.Key,

lists = y.Select(p => new a

{

name = p.c.ItemName

}).ToList()

}).ToList();

return View(data1.ToList());

}