如何绑定外键？ 如何在控制器类中使用外键创建Model对象？

Question

我有以下表格关系：

ProfileMeta 1 ----- 0...1 ProfileDetail

点击“ Profile/Create页面上的提交后，我收到了运行时错误

Cannot insert the value NULL into column 'ID', table 'ContosoUniversity1.dbo.ProfileMeta'; column does not allow nulls. INSERT fails.

我在Models / ProfileDetail.cs中正确引用了ProfileMeta作为ForeignKey：

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Web;

namespace ContosoUniversity.Models
{
    //ProfileMeta is Principal Class
    //ProfileDetail is Dependent Class
    public class ProfileDetail
    {

        //classNameID or ID is interpreted by EF as PK.
        public int ID { get; set; }

        //ForeignKey("<Navigation Property Name>")
        [Key, ForeignKey("ProfileMeta")] 
        [DatabaseGeneratedAttribute(DatabaseGeneratedOption.None)]
        public int ProfileMetaID {get; set;}
        public string UserName { get; set; }
        public string Age { get; set; }
        public string Location { get; set; }
        public string Gender { get; set; }

        //Optional Details
        public string HighSchool { get; set; }
        public string UndergraduateSchool { get; set; }
        public string GraduateSchool { get; set; }

        public virtual ProfileMeta ProfileMeta { get; set; }


    }

}

型号/ ProfileMeta.cs：

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Web;

namespace ContosoUniversity.Models
{
    //ProfileMeta is Principal
    //ProfileDetail is Dependent
    public class ProfileMeta
    {

        public int ID { get; set; }
        public string Username { get; set; }
        public string password { get; set; }

        public virtual ProfileDetail ProfileDetail {get; set;}
        public virtual ICollection<MessageDetail> MessageDetails { get; set; }
        public virtual ICollection<ConversationMeta> ConversationMetas { get; set; }
    }
}

对于功能注册/注册页面，我创建了一个模型：“Register”，它引用了ProfileMeta和ProfileDetail。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace ContosoUniversity.Models
{
    public class Register
    {
        public ProfileMeta ProfileMeta_ { get; set; }
        public ProfileDetail ProfileDetail_ { get; set; }
    }
}

查看/资料/ Create.cshtml：

@model ContosoUniversity.Models.Register
@{
    ViewBag.Title = "Create";
}

<h2>Create</h2>


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

    <div class="form-horizontal">
        <h4>Profile</h4>
        <hr />
        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        <div class="form-group">
            @Html.LabelFor(model => model.ProfileMeta_.Username, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.ProfileMeta_.Username, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.ProfileMeta_.Username, "", new { @class = "text-danger" })
            </div>
        </div>

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

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

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

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

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

        <div class="form-group">
            @Html.LabelFor(model => model.ProfileDetail_.GraduateSchool, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.ProfileDetail_.GraduateSchool, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.ProfileDetail_.GraduateSchool, "", new { @class = "text-danger" })
            </div>
        </div>
        <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <input type="submit" value="Create" class="btn btn-default" />
            </div>
        </div>
    </div>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

ProfileController.cs：

    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Create(Register register)
    {
        if (ModelState.IsValid)
        {
            //Add 1 ProfileMeta row and 1 linked ProfileDetail row
            ProfileMeta profileMeta = new ProfileMeta();

            profileMeta.Username = register.ProfileMeta_.Username;
            profileMeta.password = register.ProfileMeta_.password;

            ProfileDetail profileDetail = new ProfileDetail();
            //profileDetail.ID = register.ProfileDetail_.ID;

            //How to assign FK below?
            profileDetail.ProfileMetaID = register.ProfileDetail_.ID;
            profileDetail.UserName = register.ProfileDetail_.UserName;
            profileDetail.Age = register.ProfileDetail_.Age;
            profileDetail.Location = register.ProfileDetail_.Location;
            profileDetail.ProfileMeta = profileMeta;
            //profileDetail.UserName = register.ProfileDetail_.UserName;
            //profileDetail.Age = register.ProfileDetail_.Age;
            //profileDetail.Location = register.ProfileDetail_.Location;


            profileMeta.ProfileDetail = profileDetail;               

            db.ProfileMetas.Add(profileMeta);
            db.ProfileDetails.Add(profileDetail);

            db.SaveChanges();
            return RedirectToAction("Index");
        }

        return View(register);
    }

为什么我不能添加一行ProfileMeta和相应的ProfileDetail行？ 我以为数据库会自动生成主键（或ID）。

是否有必要在控制器中为给定的Model对象显式设置导航属性？ 另外，我是否需要在我创建的ProfileDetail对象中显式设置外键：“ProfileMetaID”？

Answer 1

首先，我想建议使用EF代码约定，而不是明确定义EF中的关系（您的声明是正确的，它只是个人偏好对我而言，我认为它更清洁）。

所以不是这样的：

    //ForeignKey("<Navigation Property Name>")
    [Key, ForeignKey("ProfileMeta")] 
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.None)]
    public int ProfileMetaID {get; set;}
    public virtual ProfileMeta ProfileMeta { get; set; }

你可以做：

 public int ProfileMetaID { get; set; }
 public virtual ProfileMeta profileMeta { get; set; }

EF将在DB中自动为您创建FK 。

至于您的问题，我强烈建议您使用ViewModel并包含您想要使用的所有属性。 但是如果要使用现有模型，可以使用ProfileMeta作为基本模型，并使用model.profileDetail.Age绑定ProfileDetail的值。

这是一个例子：

你的型号（短版）

public class ProfileDetail
    {

        [Key, DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
        public int ID { get; set; }
        public string UserName { get; set; }
        public string Age { get; set; }
        public string Location { get; set; }
        public string Gender { get; set; }
        public int ProfileMetaID { get; set; }
        public virtual ProfileMeta profileMeta { get; set; }

    }
    public class ProfileMeta
    {

[Key, DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
            public int ID { get; set; }
            public string Username { get; set; }
            public string password { get; set; }
            public virtual ProfileDetail profileDetail {get; set;}
        }

你的控制器:(不需要显式设置属性的值，因为关系和EF会处理它。）

[HttpGet]
        public ActionResult Create()
        {
            return View(new ProfileMeta());
        }
     [HttpPost]

     [ValidateAntiForgeryToken]
         public ActionResult Create(Register register)
            {
                if (ModelState.IsValid)
                 {            
                    db.ProfileMetas.Add(profileMeta);
                    db.ProfileDetails.Add(profileDetail);
                    db.SaveChanges();
                 }
           }

在您的视图中（只是一个快照）

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

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

最后，这是一个说明整个概念的小提琴： https ： //dotnetfiddle.net/N0prMA

在小提琴中，您将看到如果您提供年龄，它将提交回来并在页面中显示。