获取数据库的字段的问题

C# code

   sb.AppendFormat("select UserName UserPwd from admin" +
                    " where UserName='{0}' and UserName='{1}'", userName,userPwd);
            Datebase datebase = new Datebase();
            try
             {
                SqlCommand command = new SqlCommand(sb.ToString(),datebase.Connection);
                datebase.Open();
                SqlDataReader get = command.ExecuteReader();
                get.Read();
                string getUserName = (string)get["UserName"];//将查询得到的数据库字段赋值
                string getUserPwd = (string)get["UserPwd"];
             
                if (getUserName.Equals(userName))//判断输入的账号密码是否与获取的字段数据相等
                {
                    message = "用户名不存在";
                    isValiUser = true;
                }
                else if (getUserPwd.Equals(userPwd))
                {
                    message = "密码不存在";
                    isValiUser = false;
                }

我现在就是要向把两个列的数据分别赋值给 getUserPwd getUserName 我上面这些的话异常
用getString 赋值也没成功

select UserName UserPwd from [admin]