如何为 ASP.NET 中的现有对象添加值

Question

我在向 asp.net 中的现有对象添加值时遇到问题，我尝试查找示例但总是失败，当从输入表单发布数据时，只是名称和城市，但在控制器中我想添加地址数据（静态数据），请帮我解决这个问题。

创建.cshtml：

@model CRUDinMVC.Models.StudentModel


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

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

<script src="~/Scripts/jquery-3.4.1.min.js"></script>
<script src="~/Scripts/jquery.validate.min.js"></script>
<script src="~/Scripts/jquery.validate.unobtrusive.min.js"></script>

StudentModel.cs：

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

namespace CRUDinMVC.Models
{
    public class StudentModel
    {
        [Display(Name = "Id")]
        public int Id { get; set; }

        [Required(ErrorMessage = "First name is required.")]
        public string Name { get; set; }

        [Required(ErrorMessage = "City is required.")]
        public string City { get; set; }
    }
}

StudentDBHandle.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;

namespace CRUDinMVC.Models
{
public class StudentDBHandle
    {
private SqlConnection con;
        private void connection()
        {
            string constring = ConfigurationManager.ConnectionStrings["studentconn"].ToString();
            con = new SqlConnection(constring);
        }

        // **************** ADD NEW STUDENT *********************
        public bool AddStudent(StudentModel smodel)
        {
            connection();
            SqlCommand cmd = new SqlCommand("AddNewStudent", con);
            cmd.CommandType = CommandType.StoredProcedure;

            cmd.Parameters.AddWithValue("@Name", smodel.Name);
            cmd.Parameters.AddWithValue("@City", smodel.City);
            cmd.Parameters.AddWithValue("@Address", smodel.Address);

            con.Open();
            int i = cmd.ExecuteNonQuery();
            con.Close();

            if (i >= 1)
                return true;
            else
                return false;
        }
}
}

StudentController.cs :（在这个控制器中，我想在传递给 StudentDBHandle.cs 之前添加地址值）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.IO;
using System.Web.Mvc;
using CRUDinMVC.Models;
using System.Diagnostics;

namespace CRUDinMVC.Controllers
{
    public class StudentController : Controller
    {
        // 1. *************RETRIEVE ALL STUDENT DETAILS ******************
        // GET: Student
        public ActionResult Index()
        {
            StudentDBHandle dbhandle = new StudentDBHandle();
            ModelState.Clear();
            return View(dbhandle.GetStudent());
        }

        // 2. *************ADD NEW STUDENT ******************
        // GET: Student/Create
        public ActionResult Create()
        {
            return View();
        }

        // POST: Student/Create
        [HttpPost]
        public ActionResult Create(StudentModel smodel) **// in this function I wanna add Address value, How to do it ?**
        {
            try
            {
                if (ModelState.IsValid)
                {
                    StudentDBHandle sdb = new StudentDBHandle(); 
                    if (sdb.AddStudent(smodel))
                    {
                        ViewBag.Message = "Student Details Added Successfully";
                        ModelState.Clear();
                    }
                }
                return RedirectToAction("Index");
            }
            catch
            {
                return View();
            }
        }
    }
}

请帮助我，谢谢。

Answer 1

我会使用 Viewmodel。这是一个不同的类，它允许您在不直接访问数据对象的情况下映射属性。

public class StudentViewmodel
{
    [Display(Name = "Id")]
    public int Id { get; set; }

    [Required(ErrorMessage = "First name is required.")]
    public string Name { get; set; }

    [Required(ErrorMessage = "City is required.")]
    public string City { get; set; }

    public string Address { get; set; }
}

现在不要在您的视图上使用StudentModel，而是使用StudentViewmodel，它公开了一个地址属性，您可以将您的地址信息添加到：

// POST: Student/Create
[HttpPost]
public ActionResult Create(StudentViewmodel smodel)
{
    try
    {
        if (ModelState.IsValid)
        {
            smodel.Address = "you put your address information here.";
            StudentDBHandle sdb = new StudentDBHandle();
            if (sdb.AddStudent(smodel))
            {
                ViewBag.Message = "Student Details Added Successfully";
                ModelState.Clear();
            }
        }
        return RedirectToAction("Index");
    }
    catch
    {
        return View();
    }
}

记得更改StudentDBHandle 中的参数类型，以便它也使用StudentViewmodel 对象。

您甚至不必进行额外的映射，因为 Viewmodel 包含与您的数据模型相同的属性名称。

public bool AddStudent(StudentViewmodel smodel)
{
    connection();
    SqlCommand cmd = new SqlCommand("AddNewStudent", con);
    cmd.CommandType = CommandType.StoredProcedure;

    cmd.Parameters.AddWithValue("@Name", smodel.Name);
    cmd.Parameters.AddWithValue("@City", smodel.City);
    cmd.Parameters.AddWithValue("@Address", smodel.Address);

    con.Open();
    int i = cmd.ExecuteNonQuery();
    con.Close();

    // You can simplify your return, too.
    return i >= 1;
    //if (i >= 1)
    //  return true;
    //else
    //  return false;
}