public class UserDetail
    {
        [Required]
        public string username { get; set; }
        [Required]
        public string name { get; set; }
        public LogInDetail LogInDetail { get; set; }
    }

public class LogInDetail
    {
        [Required]
        public string username { get; set; }
        [Required]
        public string password { get; set; }

        public UserDetail UserDetail { get; set; }
    }

@using (Html.BeginForm())
        {
            @Html.LabelFor(m=>m.LogInDetail.username)
            @Html.EditorFor(m=>m.LogInDetail.username)
            @Html.ValidationMessageFor(m=>m.LogInDetail.username)

            @Html.LabelFor(m=>m.LogInDetail.password)
            @Html.EditorFor(m=>m.LogInDetail.password)
            @Html.ValidationMessageFor(m=>m.LogInDetail.password)
            <input type="submit" value="Submit" />
        }