winform 随机选人页面的实现

我想实现一个随机选人的页面，每次选中之后则修改选人的权重，如下

Rollcall.cs

using Business;
using Common.RestSharp;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.OleDb;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
 
namespace QJKT
{
   
    public partial class Rollcall : Form
    {
   
        List<Student> handstulist = new List<Student>();//举手学生列表
        List<Student> stuitems = new List<Student>();//学生加权重随即乱序列表
        List<string> selStulist = new List<string>();//学生查询列表
        public DataTable dt_exp = null;
        Boolean flag = false;
        public Rollcall()
        {
   
            this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
            InitializeComponent();
            //加载学生名单
            dt_exp = GetStudentTable();
            this.dataGridView1.DataSource = dt_exp;
            this.label1.Text = "请点击选人方式";
            //表格界面优化
            this.dataGridView1.ColumnHeadersDefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
            this.dataGridView1.DefaultCellStyle.Font = new Font("宋体", 13);
            this.dataGridView1.EnableHeadersVisualStyles = false;
            this.dataGridView1.ColumnHeadersDefaultCellStyle.Font = new Font("宋体", 12, FontStyle.Bold);
            this.dataGridView1.ColumnHeadersDefaultCellStyle.ForeColor = Color.Purple;
        }
        private static Rollcall rollcall = null;//加载一个静态的私有的成员变量

        public static Rollcall RollcallInstance()//返回这个实例化后的静态变量
        {
   
            if (rollcall == null || rollcall.IsDisposed)
            {
   
                rollcall = new Rollcall();
            }
            return rollcall;
        }
        private void button1_Click(object sender, EventArgs e)
        {
   
            dt_exp = GetStudentTable();
            this.dataGridView1.DataSource = dt_exp;
            this.label1.Text = "请点击【开始】";
            /*OpenFileDialog ofd = new OpenFileDialog();
            ofd.InitialDirectory = Application.StartupPath;
            ofd.Title = "请选择要导入的文件";
            ofd.Filter = "csv文件|*.csv";
            if (ofd.ShowDialog() == DialogResult.OK)
            {
                //获取用户选择的文件完整路径
                string filePath = ofd.FileName;
                //获取对话框中所选文件的文件名和扩展名，文件名不包括路径
                string fileName = ofd.SafeFileName;
                dt_exp = ReadTest(filePath);
                this.dataGridView1.DataSource = dt_exp;
                this.label1.Text = "请点击【开始】";
            }*/
        }

        //读取csv文件
        private DataTable ReadTest(string filepath)
        {
   
            DataTable dt = new DataTable();

            //文件流读取
            System.IO.FileStream fs = new System.IO.FileStream(filepath, System.IO.FileMode.Open);
            System.IO.StreamReader sr = new System.IO.StreamReader(fs, Encoding.GetEncoding("gb2312"));

            string tempText = "";
            bool isFirst = true;
            while ((tempText = sr.ReadLine()) != null)
            {
   
                string[] arr = tempText.Split(new char[] {
    ',' }, StringSplitOptions.RemoveEmptyEntries);

                //一般第一行为标题，所以取出来作为标头
                if (isFirst)
                {
   
                    foreach (string str in arr)
                    {
   
                        dt.Columns.Add(str);
                    }
                    isFirst = false;
                }
                else
                {
   
                    //从第二行开始添加到datatable数据行
                    DataRow dr = dt.NewRow();
                    for (int i = 0; i < dt.Columns.Count; i++)
                    {
   
                        dr[i] = i < arr.Length ? arr[i] : "";
                    }
                    dt.Rows.Add(dr);
                }
            }
            //展示到页面
            //关闭流
            sr.Close(); fs.Close();

            return dt;
        }
        /// <summary>
        /// 获取课堂名单，权值
        /// </summary>
        /// <returns></returns>
        private DataTable GetStudentTable()
        {
   
            //学生
            List<string> students = new List<string>( );
            DataTable dt = new DataTable();
            if (Classes.slist.Count > 0)
            {
   
                dt.Columns.Add("序号");
                dt.Columns.Add("学号");
                dt.Columns.Add("姓名"