即使没有Model [必需]属性，也需要MVC5 View控件，为什么？我不需要

Question

我有一个带有提交按钮的视图。它具有多个控件，其中很多是DropDownLists。在“我的模型”类中，我仅具有某些必需的属性。除非选择了我所有的下拉列表，否则我的页面不会提交，这是我不希望使用它们时需要的额外控件。知道为什么会这样吗？这是我的代码。 （这让我有了软件类型，来源和制造商）

//Model
[Required]
        [Display(Name = "Part Book / Category")]
        public string PartBook { get; set; }
        //decimal
        public string PartNextNumber { get; set; }

        [Display(Name = "Today's Date")]
        public DateTime DateEntered { get; set; }

        [Required]
        [Display(Name = "Entered By")]
        public int EnteredBy { get; set; }

        [Display(Name = "Software Type")]
        public int SoftwareType { get; set; }

        //unsure of this one ********************
        [Display(Name = "Assembly Number")]
        public string UsedOnAssembly { get; set; }
        // INT OR BOOL ?
        [Display(Name = "Global Part")]
        public bool GlobalPart { get; set; }

        //[Required]
        public int Source { get; set; }

        public int Manufacturer { get; set; }

        [Display(Name = "Manufacturer Part Number")]
        public string ManufacturerPartNumber { get; set; }
//View
t-danger" })

                        <div class="panel-body">
<div class="col-md-6 col-lg-6">
                                    @*   Change to DropDownList of ParkBooks   *@
                                    @*@onchange="location.href='"+
                                        Url.Action("DoPartBookFunc","Parts", "parkbookDDL")+"'" *@

                                    @Html.DropDownListFor(x => x.PartBook,
                                     (IEnumerable<SelectListItem>) ViewBag.PartBookDDL,
                                     "", new { @class = "form-control" })
                                    @Html.ValidationMessageFor(x => x.PartBook,
                                     "", new { @class = "text-danger" })
                                </div>
<div class="form-group row">
                                <div class="col-md-3 col-lg-3">
                                    @Html.LabelFor(x => x.SoftwareType,
                                     htmlAttributes: new { @class = "control-label" })
                                </div>
                                <div class="col-md-6 col-lg-6">
                                    @Html.DropDownListFor(x => x.SoftwareType,
                                     (IEnumerable<SelectListItem>)ViewBag.SoftwareTypeDDL,
                                     "", new { @class = "form-control" })
                                    @Html.ValidationMessageFor(x => x.SoftwareType, "",
                                     new { @class = "text-danger" })
                                </div>
<div class="form-group row">
                                <div class="col-md-3 col-lg-3">
                                    @Html.LabelFor(x => x.Source,
                                     htmlAttributes: new { @class = "control-label" })
                                </div>
                                <div class="col-md-9 col-lg-9">
                                    @Html.DropDownListFor(x => x.Source,
                                     (IEnumerable<SelectListItem>) ViewBag.SourceDDL,
                                     "", new { @class="form-control" })
                                    @Html.ValidationMessageFor(x => x.Source,
                                     "", new { @class = "text-danger" })
                                </div>
                            </div>

                            <div class="form-group row">
                                <div class="col-md-3 col-lg-3">
                                    @Html.LabelFor(x => x.Manufacturer,
                                     htmlAttributes: new { @class = "control-label" })
                                </div>
                                <div class="col-md-6 col-lg-6">
                                    @Html.DropDownListFor(x => x.Manufacturer,
                                     (IEnumerable<SelectListItem>)ViewBag.ManufacturerDDL,
                                     "", new { @class="form-control" })
                                    @Html.ValidationMessageFor(x => x.Manufacturer,
                                     "", new { @class = "text-danger" })