asp.net list 方法调不到

为什么这样？

 public Course(string name, string courseName, int score, int credit)
你的构造函数有3个参数

你不能
Course s = new Course();
而要
Course s = new Course("姓名", "书名", xxx, xx);这样调用

using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
namespace xsgl
{

  public  class Course
    {
        private string courseName;
        private int credit;
        //课程名称
        public string CourseName
        {
            get
            {
                return courseName;
            }
            set
            {
                courseName = value;
            }
        }
        //课程学分
        public int Credit
        {
            get
            {
                return credit;
            }
            set
            {
                credit = value;
            }
        }
        //学生姓名
        public string Name
        {
            get;
            set;
        }
        //成绩分数
        public int Score
        {
            get;
            set;
        }
        //计算总分
        public int Zf()
        {
            return Credit + Score;

        }
        public Course(string name, string courseName, int score, int credit)
        {
            Name = name;//姓名
            CourseName = courseName; //书名
            Score = score; //成绩
            Credit = credit;//学分
        }
    }
}

Course类在哪里定义的，有没有using对应的命名空间，是不是public类型的

都在同一命名空间下

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

namespace xsgl
{
public partial class _Default : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void Button1_Click(object sender, EventArgs e)
    {

        string name;//姓名
        string courseName;//课程名  
        int score;//成绩
        int credit;//学分
        List<Course> students = new List<Course>();            
        name = TextBox1.Text;
        courseName = TextBox3.Text;
        credit =Convert.ToInt32( TextBox2.Text);
        score =Convert.ToInt32( TextBox4.Text);
        students.ADD(new Course(name,courseName,score,credit));

    }
}

}

这个也是要加uing吗？

这个怎么才能将排名显示到 label 里面