Try this,
Create a class with the properties as
public class Student
{
public int Id { get; set; }
public float Cosine { get; set; }
}
and your method should be edited as
public List<student> GetStuCosineSimilarity()
{
List<student> lst = new List<student>();
lst = (from s in DB.Students
select new Student()
{
Id = s.StudentId,
Cosine = s.cosineSimilarity
}).ToList();
lst = lst.OrderBy(k => k.Cosine).ToList();
return lst;
}