c# - ASP.NET MVC : How to use linq lambda expression with a ViewModel to get data?

Question

如何使用 linq 表达式来使用 ViewModel 从其中一个领域模型中获取数据？当我尝试获取与用户输入的 item_id 关联的 inv_mast_uid 时，我只得到一个 0 而不是像 10345 这样的唯一整数。我确实从 ViewModel 获取了所有其他必要的数据。

这是显示我的三个表的图像:

这是我尝试创建一个 ViewModel 以用于向项目添加新的备用代码:

public class AlternateCodeViewModel
{


    [Key]
    [Column(Order = 0)]
    public int inv_mast_uid { get; set; }

    [Key]
    [Column(Order = 1)]
    [StringLength(50)]
    [Display(Name = "Alternate Code")]
    public string Alternate_Code_Item_ID { get; set; }

    [Key]
    [Column(Order = 2)]
    public int Alternate_Code_Brand_ID { get; set; }

    [Required]
    [StringLength(1)]
    [Display(Name = "Exact Flag")]
    public string Exact_Flag { get; set; }

    [Required]
    [StringLength(1)]
    [Display(Name = "Delete Flag")]
    public string Delete_Flag { get; set; }

    public string item_id { get; set; }


    public IEnumerable<web2_item_brands> web2_item_brands { get; set; }

    [ForeignKey("inv_mast_uid")]
    public inv_mast inv_mast { get; set; }

    public AlternateCodeViewModel()
    {
        Delete_Flag = "N";
        Exact_Flag = "Y";
    }
}

这是我的 Controller 方法:

[HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult AddAltCode(AlternateCodeViewModel avm)
    {
        if (ModelState.IsValid)
        {

            var newCode = new web2_item_alternate_code
            {
                inv_mast_uid = avm.inv_mast_uid,
                Alternate_Code_Item_ID = avm.Alternate_Code_Item_ID,
                Alternate_Code_Brand_ID = avm.Alternate_Code_Brand_ID,
                Delete_Flag = avm.Delete_Flag,
                Exact_Flag = avm.Exact_Flag
            };

            db.web2_item_alternate_code.Add(newCode);
            db.SaveChanges();
            return RedirectToAction("AltCodeIndex");
        }
        return View();
    }

如果它有帮助，这是一张显示我的 newCode 对象的图像，它缺少 inv_mast_uid 属性:

编辑:按照建议，已添加以下附加信息

初始化 View 的我的 Controller :

ublic ActionResult AddAltCode()
    {    
        ViewBag.brandsdd = new SelectList(db.web2_item_brands.OrderBy(x => x.brand_name), "item_brand_uid", "brand_name");
        return View();
    }

我的看法:

@using System.Web.Mvc.Html
@using System.Linq;
@model Non_P21_Quote_System_v1._0.ViewModels.AlternateCodeViewModel

@{
    ViewBag.Title = "AddAltCode";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Add Alternate Code</h2>


@using (Html.BeginForm())
{
    @Html.AntiForgeryToken()

    <div class="form-horizontal">

    <hr />
    @Html.ValidationSummary(true, "", new { @class = "text-danger" })


    <div class="form-group">
        @Html.LabelFor(model => model.item_id, "Item ID", htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.item_id, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.item_id, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.web2_item_brands, "Brand Name", htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownList("Alternate_code_brand_id", new SelectList(ViewBag.brandsdd, "Value", "Text") , htmlAttributes: new { @class = "form-control" })
                @*@Html.ValidationMessageFor(model => model.web2_item_brands, "", new { @class = "text-danger" })*@
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.Alternate_Code_Item_ID, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.Alternate_Code_Item_ID, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.Alternate_Code_Item_ID, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        <div class="col-md-offset-2 col-md-10">
            <input type="submit" value="Add" class="btn btn-default" />
        </div>
    </div>
</div>

我的观点的图像:

Answer 1

正如我从您的代码中看到的，您无法将“inv_mast_uid”和“inv_mast inv_mast”添加为整数属性。您需要将“inv_mst”和“web2_item_brands”作为对象添加到“web2_alternate_code”，并在填充后单独保存它们。当你想读取相关对象时需要调用“include”时也是如此。

所以最好的方法是在“web2_alternate_code”中添加这两个对象，并使用“web2_alternate_code”构造函数实例化它们。之后，您可以将任何数据添加到 [HttpPost] 上的那些对象。