asp.net core 2.1中新的创建dbcontext类对象的问题

我是.net core 2.1的新手

我正在以代码优先方法使用.net core 2.1

问题是当我创建一个新的对象dbcontext类然后给出错误时,请参见下一行

dbcontextstudent db=new dbcontextstudent();  //here give an red line

appsettings.json

 },
  "ConnectionStrings": {
    "sqlserverconn": "Server=DEVISSHAHID; Database=studdbs; User id=xxxx;Password=xxxxx;"
  },

启动文件

 public void ConfigureServices(IServiceCollection services)
        {
            //connection string
            services.AddDbContext<DbContext>(options => options.UseSqlServer(Configuration.GetConnectionString("sqlserverconn")));

student.cs

namespace WebApplication1.Models
{
    public class student
    {
        [Key]
        public int studid { get; set; }

        public string studname { get; set; }

        public string studsalary { get; set; }

        public int studage { get; set; }
    }
}

dbcontextstudent.cs

namespace WebApplication1.Models
{
    public class dbcontextstudent : DbContext
    {
        public dbcontextstudent(DbContextOptions<dbcontextstudent> options) : base(options)
        {

        }

        public DbSet<student> stud { get; set; }
    }
}

HomeController.cs

enter image description here

我不懂上面的智能

我按照智能感知编写代码,但仍然出现错误,我知道错误很明显但无法解决

我在哪个地方做错了?