请教一个集合排序的问题

[ahking]

 public class Student
    {
        public string First { get; set; }
        public string Last { get; set; }
        public int ID { get; set; }
    }

    public static List<Student> GetStudents()
    {
        // Use a collection initializer to create the data source. Note that each element
        //  in the list contains an inner sequence of scores.
        List<Student> students = new List<Student>
        {
           new Student {First="Svetlana", Last="Omelchenko", ID=111},
           new Student {First="Claire", Last="O'Donnell", ID=112},
           new Student {First="Sven", Last="Mortensen", ID=113},
           new Student {First="Cesar", Last="Garcia", ID=114},
           new Student {First="Debra", Last="Garcia", ID=115} 
        };

        return students;

    }

GetStudents().OrderBy(u => u.First)
GetStudents().OrderBy(u => u.Last)
GetStudents().OrderBy(u => u.ID)

可以排序，如果被排序的字段是个变量，应该怎么写呢？
如 string field="First";
GetStudents().OrderBy(u => u.?)

[Dogfish]

使用反射（Reflection）

var dynamicPropFromStr = typeof(Student).GetProperty("First"); 
GetStudents().OrderBy(u=>dynamicPropFromStr.GetValue(u, null))