关于ADO.NET数据库开发中出现的问题！

vs报错：

控制器代码：using Microsoft.AspNetCore.Mvc;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Data;
using System.Data.SqlClient;
using WebApplication9.Models;

namespace WebApplication9.Controllers
{
public class HomeController : Controller
{
public IActionResult Index() //首页
{
return View();
}

    public IActionResult Register() //用户注册页
    {
        return View();
    }

    public IActionResult RegisterSubmit1() //用户注册页单击submit按钮w为数据库表插入一条新记录
    {
        #region 方法一（不推荐）：不使用模型
        string u1 = HttpContext.Request.Form["u1"];
        string p1 = HttpContext.Request.Form["p1"];
        string ph1 = HttpContext.Request.Form["ph1"];
        string addr1 = HttpContext.Request.Form["addr1"];

        SqlConnection mcon = new SqlConnection("Data source=.;database=web;integrated security=ture");
        mcon.Open();
        string sql1 = "select * from mymember where username='" + u1 + "'";   //查询数据库
        SqlCommand mcom = new SqlCommand(sql1, mcon);
        string a = (string)mcom.ExecuteScalar();
        if (a == null)
        {
            string inssql = "insert into mymember values('" + u1 + "','" + p1 + "','" + ph1 + "','" + addr1 + "','头像待传')";     //写入数据库
            SqlCommand inscom = new SqlCommand(inssql, mcon);
            inscom.ExecuteNonQuery();
            ViewData["msg1"] = "注册成功！";
        }
        else
        {
            ViewData["msg1"] = "该用户名已经存在！";
        }
        mcon.Close();
        return View("/Views/Home/Register.cshtml");

        #endregion
    }
}

}
软件：vs2022 . sql sever management studio

视图页的model怎么申明的，代码发出来

报错文本信息发一下，不要截图。