C# Mvc-带viewmodel的表单

我在mvc中工作，在我的视图中有一个表单，它从我的viewmodel接收一个selectlist，将值插入我的dropdownlist

但是在提交表单时，什么都不起作用，我也弄不清楚到底是怎么回事

提交表单时，我的数据库中会出现null

有人能帮我解决这个问题吗

这是我的密码： 查看：

model MyProject.Models.ViewModel
@using(Html.BeginForm()) {
    @Html.DropDownListFor(o => o.cp.Companylist,Model.cp.Companylist)
     @Html.EditorFor(o => o.md.title)
     @Html.EditorFor(o => o.md.edition)
    @Html.EditorFor(o => o.md.number)

  <input type="submit" name="submit" value="Add New">
}

  public ActionResult Create()
        {   ViewModel vm = new ViewModel ();
            return View(vm);
        }

        //
        // POST: Create

        [HttpPost]
        public ActionResult Create(Mydata model)
        {
            if (ModelState.IsValid)
            {
                db.Res.Add(model);
                db.SaveChanges();
                return RedirectToAction("Index","AdminPanel");
            }

            return View(model);
        }

 public class ViewModel
    {
        public Mydata md { get; set; }
        public Company cp { get; set; }
    }

 public class Mydata
    {
        public int ID { get; set; }
        public string company_name{ get; set; }
        public string title{ get; set; }
        public string edition{ get; set; }
        public string number{ get; set; }
    }
public class DefaultConnection : DbContext
    {
        public DbSet<Mydata> Res{ get; set; }
    }

 public class Company
    {
        public int id { get; set; }
        public string name{ get; set; }
        public SelectList Companylist{ get; set; }  

        public Company()
        {
            Companylist= GetCompanies();
        }

        public SelectList GetCompanies()
        {
            var list = new List<SelectListItem>();
            string connection = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;

            using (var con = new SqlConnection(connection))
            {
                con.Open();
                using (var command = new SqlCommand("SELECT * FROM MyCompanies", con))
                {
                    SqlDataReader reader = command.ExecuteReader();
                    while (reader.Read())
                    {
                        //string id = reader[0] as string;
                        string name_company= reader[1] as string;
                        list.Add(new SelectListItem() { Text = name_company, Value = name_company});
                    }
                }
                con.Close();
            }
            return new SelectList(list, "Value", "Text");
        }
}

型号：

model MyProject.Models.ViewModel
@using(Html.BeginForm()) {
    @Html.DropDownListFor(o => o.cp.Companylist,Model.cp.Companylist)
     @Html.EditorFor(o => o.md.title)
     @Html.EditorFor(o => o.md.edition)
    @Html.EditorFor(o => o.md.number)

  <input type="submit" name="submit" value="Add New">
}

  public ActionResult Create()
        {   ViewModel vm = new ViewModel ();
            return View(vm);
        }

        //
        // POST: Create

        [HttpPost]
        public ActionResult Create(Mydata model)
        {
            if (ModelState.IsValid)
            {
                db.Res.Add(model);
                db.SaveChanges();
                return RedirectToAction("Index","AdminPanel");
            }

            return View(model);
        }

 public class ViewModel
    {
        public Mydata md { get; set; }
        public Company cp { get; set; }
    }

 public class Mydata
    {
        public int ID { get; set; }
        public string company_name{ get; set; }
        public string title{ get; set; }
        public string edition{ get; set; }
        public string number{ get; set; }
    }
public class DefaultConnection : DbContext
    {
        public DbSet<Mydata> Res{ get; set; }
    }

 public class Company
    {
        public int id { get; set; }
        public string name{ get; set; }
        public SelectList Companylist{ get; set; }  

        public Company()
        {
            Companylist= GetCompanies();
        }

        public SelectList GetCompanies()
        {
            var list = new List<SelectListItem>();
            string connection = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;

            using (var con = new SqlConnection(connection))
            {
                con.Open();
                using (var command = new SqlCommand("SELECT * FROM MyCompanies", con))
                {
                    SqlDataReader reader = command.ExecuteReader();
                    while (reader.Read())
                    {
                        //string id = reader[0] as string;
                        string name_company= reader[1] as string;
                        list.Add(new SelectListItem() { Text = name_company, Value = name_company});
                    }
                }
                con.Close();
            }
            return new SelectList(list, "Value", "Text");
        }
}

Mydata-型号：

model MyProject.Models.ViewModel
@using(Html.BeginForm()) {
    @Html.DropDownListFor(o => o.cp.Companylist,Model.cp.Companylist)
     @Html.EditorFor(o => o.md.title)
     @Html.EditorFor(o => o.md.edition)
    @Html.EditorFor(o => o.md.number)

  <input type="submit" name="submit" value="Add New">
}

  public ActionResult Create()
        {   ViewModel vm = new ViewModel ();
            return View(vm);
        }

        //
        // POST: Create

        [HttpPost]
        public ActionResult Create(Mydata model)
        {
            if (ModelState.IsValid)
            {
                db.Res.Add(model);
                db.SaveChanges();
                return RedirectToAction("Index","AdminPanel");
            }

            return View(model);
        }

 public class ViewModel
    {
        public Mydata md { get; set; }
        public Company cp { get; set; }
    }

 public class Mydata
    {
        public int ID { get; set; }
        public string company_name{ get; set; }
        public string title{ get; set; }
        public string edition{ get; set; }
        public string number{ get; set; }
    }
public class DefaultConnection : DbContext
    {
        public DbSet<Mydata> Res{ get; set; }
    }

 public class Company
    {
        public int id { get; set; }
        public string name{ get; set; }
        public SelectList Companylist{ get; set; }  

        public Company()
        {
            Companylist= GetCompanies();
        }

        public SelectList GetCompanies()
        {
            var list = new List<SelectListItem>();
            string connection = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;

            using (var con = new SqlConnection(connection))
            {
                con.Open();
                using (var command = new SqlCommand("SELECT * FROM MyCompanies", con))
                {
                    SqlDataReader reader = command.ExecuteReader();
                    while (reader.Read())
                    {
                        //string id = reader[0] as string;
                        string name_company= reader[1] as string;
                        list.Add(new SelectListItem() { Text = name_company, Value = name_company});
                    }
                }
                con.Close();
            }
            return new SelectList(list, "Value", "Text");
        }
}

公共类Mydata
{
公共int ID{get；set；}
公共字符串公司名称{get；set；}
公共字符串标题{get；set；}
公共字符串版本{get；set；}
公共字符串编号{get；set；}
}
公共类DefaultConnection:DbContext
{
公共数据库集Res{get；set；}
}

公司-型号：

model MyProject.Models.ViewModel
@using(Html.BeginForm()) {
    @Html.DropDownListFor(o => o.cp.Companylist,Model.cp.Companylist)
     @Html.EditorFor(o => o.md.title)
     @Html.EditorFor(o => o.md.edition)
    @Html.EditorFor(o => o.md.number)

  <input type="submit" name="submit" value="Add New">
}

  public ActionResult Create()
        {   ViewModel vm = new ViewModel ();
            return View(vm);
        }

        //
        // POST: Create

        [HttpPost]
        public ActionResult Create(Mydata model)
        {
            if (ModelState.IsValid)
            {
                db.Res.Add(model);
                db.SaveChanges();
                return RedirectToAction("Index","AdminPanel");
            }

            return View(model);
        }

 public class ViewModel
    {
        public Mydata md { get; set; }
        public Company cp { get; set; }
    }

 public class Mydata
    {
        public int ID { get; set; }
        public string company_name{ get; set; }
        public string title{ get; set; }
        public string edition{ get; set; }
        public string number{ get; set; }
    }
public class DefaultConnection : DbContext
    {
        public DbSet<Mydata> Res{ get; set; }
    }

 public class Company
    {
        public int id { get; set; }
        public string name{ get; set; }
        public SelectList Companylist{ get; set; }  

        public Company()
        {
            Companylist= GetCompanies();
        }

        public SelectList GetCompanies()
        {
            var list = new List<SelectListItem>();
            string connection = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;

            using (var con = new SqlConnection(connection))
            {
                con.Open();
                using (var command = new SqlCommand("SELECT * FROM MyCompanies", con))
                {
                    SqlDataReader reader = command.ExecuteReader();
                    while (reader.Read())
                    {
                        //string id = reader[0] as string;
                        string name_company= reader[1] as string;
                        list.Add(new SelectListItem() { Text = name_company, Value = name_company});
                    }
                }
                con.Close();
            }
            return new SelectList(list, "Value", "Text");
        }
}

上市公司
{
公共int id{get；set；}
公共字符串名称{get；set；}
公共选择列表公司列表{get；set；}
上市公司（）
{
Companylist=getcompanys（）；
}
public SelectList GetCompanys（）
{
var list=新列表（）；
字符串连接=ConfigurationManager.ConnectionString[“DefaultConnection”].ConnectionString；
使用（var con=newsqlconnection（连接））
{
con.Open（）；
使用（var命令=新的SqlCommand（“SELECT*FROM MyCompanies”，con））
{
SqlDataReader=command.ExecuteReader（）；
while（reader.Read（））
{
//字符串id=读卡器[0]作为字符串；
字符串名称\u company=reader[1]作为字符串；
添加（新建SelectListItem（）{Text=name\u company，Value=name\u company}）；
}
}
con.Close（）；
}
返回新的SelectList（列表，“值”、“文本”）；
}
}

问题是您正在创建一个ViewModel，但它是

md

和

cp

属性未初始化。这就是为什么在视图中调用

o.cp.Companylist

时，

o.cp

为空

由于您正在尝试

Create（）

您可能不想将现有数据分配给

MyData

或

公司

，因此您只需确保此属性已初始化。您可以在

ViewModel

构造函数中轻松完成此操作：

public class ViewModel
{
    public ViewModel()
    {
         this.md = new Mydata();
         this.cp = new Company();
    }

    public Mydata md { get; set; }
    public Company cp { get; set; }
}

---

您正在创建一个ViewModel，但它是

md

和

cp

属性未初始化（据我所见）。这就是为什么在视图中调用

o.cp.Companylist

时，

o.cp

为null.mhh。。好啊我理解。。。如何初始化它们？这解决了我的dropdownlist问题。现在，我有了一个下拉列表，其中包含数据库中的值。但是如果我提交表单以将表单中的值插入到表中，则他是insert null。。有什么想法吗？现在您的

模型绑定遇到了另一个问题。我们必须查看您的
MyData
和
Company
代码。