这个怎么写？

Question

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
namespace 登陆
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("请输入用户名：");
            string username = Console.ReadLine();
            Console.WriteLine("请输入密码：");
            string passworld = Console.ReadLine();
            //连接字符串
            string sqlstr = @"Data Source=BE541554DB7E431;Integrated Security=True";
            {
                //创建连接对象
                using (SqlConnection con = new SqlConnection(sqlstr))
                {
                    //打开数据库
                    con.Open();
                    //创建Command命令
                    using (SqlCommand cmd = new SqlCommand())
                    {
                        //先查出表中用户名对应信息
                        cmd.CommandText = "select *from Ado登陆 where UserName=" + "username";
                        using (SqlDataReader reader = cmd.ExecuteReader())
                        {
                            if (reader.Read())//如果有用户输入的数据就表示存在
                            {
                                string dbpassworld = reader.GetString(reader.GetOrdinal("passworld"));
                                if (passworld == dbpassworld)
                                {
                                    Console.WriteLine("登陆成功");
                                }
                                else
                                {
                                    Console.WriteLine("登陆失败");
                                }
                            }
                            else
                            {
                                Console.WriteLine("用户名或密码错误！");
                            }
                        }
                    }
                }
            }
        }
    }
}有问题？没反应，数据是连上了的

Answer 1

cmd.CommandText = "select *from Ado登陆 where UserName=" + "username";
=>
cmd.CommandText = "select * from Ado登陆 where UserName='" + username + "'";

Answer 2

cmd.CommandText = "select *from Ado登陆 where UserName=" + "username";
=>
cmd.CommandText = "select * from Ado登陆 where UserName='" + username + "'";

Answer 3

cmd.CommandText = "select *from Ado登陆 where UserName=" + "username";
这个是错误的，你看一下
cmd.CommandText="select * from ado-登录 where UserName='"+ username+ "'";