Question

我正在尝试学习MVC，我正在跟随位于here的Contoso大学教程

我已成功构建了一个包含学生，课程和注册数据库的项目。目前我有3个型号，

场
注册
学生

和2个控制器

的HomeController
StudentController

目前，我的路由是您使用MVC项目获得的默认路由。

        routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/{id}",
            defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }

这适用于根据StudentID

所以网址

http://localhost:49706/Student/Details/1

返回此信息

这很好用，但我试图更深入地了解路由。我想创建一个新视图，根据最后一个名称而不是学生ID显示学生详细信息。是的，我知道在现实世界中，这不是一个好主意，因为姓氏不是唯一的，但这对于这个演示很好，因为我的数据库不会变大，我知道所有姓氏目前都是独一无二的。

我做的第一件事是在我的StudentController中创建一个新的动作结果

public ActionResult Grab(string studentName)
{
    if(studentName == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }
    Student student = db.Students.Find(studentName);
    if(student == null)
    {
        return HttpNotFound();
    }
    return View(student);
}

我做的第二件事是右击“Grab”并添加了一个视图。我将视图名称称为“Grab”。将模板设置为“列表”。将Model Class设置为'Student（ContosoUniversity.Models）'。和DataContextClass为'SchoolContext（ContosoUniversity.DAL）'。

我打电话给你 http://localhost:49706/Student/Grab

我得到的400错误就像我在控制器中写的一样。但是当我尝试以下网址时

http://localhost:49706/Student/Grab/Alexander

我还得到另外400个错误。我不确定我遗漏了什么。我可以帮忙吗。

这是我的数据库的样子

我想要做的就是能够输入以下网址 http://localhost:49706/Student/Grab/ {名字}

并显示具有匹配姓氏的学生的详细信息。

感谢您的时间

修改

更新了ActionResult Grab

public ActionResult Grab(string studentName)
{
    if(studentName == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }
    Student student = db.Students.Where(student => student.LastName.Contains(studentName)).FirstOrDefault();
    if (student == null)
    {
        return HttpNotFound();
    }
    return View(student);
}

整个学生管理员

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.Linq;
using System.Net;
using System.Web;
using System.Web.Mvc;
using ContosoUniversity.DAL;
using ContosoUniversity.Models;

namespace ContosoUniversity.Controllers
{
    public class StudentController : Controller
    {
        private SchoolContext db = new SchoolContext();

        // GET: Student
        public ActionResult Index()
        {
            return View(db.Students.ToList());
        }

        // GET: Student/Details/5
        public ActionResult Details(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            Student student = db.Students.Find(id);
            if (student == null)
            {
                return HttpNotFound();
            }
            return View(student);
        }

        public ActionResult Grab(string studentName)
        {
            if(studentName == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            Student student = db.Students.Where(student => student.LastName.Contains(studentName)).FirstOrDefault();
            if (student == null)
            {
                return HttpNotFound();
            }
            return View(student);
        }

        // GET: Student/Create
        public ActionResult Create()
        {
            return View();
        }

        // POST: Student/Create
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Create([Bind(Include = "LastName, FirstMidName, EnrollmentDate")]Student student)
        {
            try
            {
                if (ModelState.IsValid)
                {
                    db.Students.Add(student);
                    db.SaveChanges();
                    return RedirectToAction("Index");
                }
            }
            catch (DataException /* dex */)
            {
                //Log the error (uncomment dex variable name and add a line here to write a log.
                ModelState.AddModelError("", "Unable to save changes. Try again, and if the problem persists see your system administrator.");
            }
            return View(student);
        }

        // GET: Student/Edit/5
        public ActionResult Edit(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            Student student = db.Students.Find(id);
            if (student == null)
            {
                return HttpNotFound();
            }
            return View(student);
        }

        // POST: Student/Edit/5
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost, ActionName("Edit")]
        [ValidateAntiForgeryToken]
        public ActionResult EditPost(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            var studentToUpdate = db.Students.Find(id);
            if (TryUpdateModel(studentToUpdate, "",
               new string[] { "LastName", "FirstMidName", "EnrollmentDate" }))
            {
                try
                {
                    db.SaveChanges();

                    return RedirectToAction("Index");
                }
                catch (DataException /* dex */)
                {
                    //Log the error (uncomment dex variable name and add a line here to write a log.
                    ModelState.AddModelError("", "Unable to save changes. Try again, and if the problem persists, see your system administrator.");
                }
            }
            return View(studentToUpdate);
        }

        // GET: Student/Delete/5
        public ActionResult Delete(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            Student student = db.Students.Find(id);
            if (student == null)
            {
                return HttpNotFound();
            }
            return View(student);
        }

        // POST: Student/Delete/5
        [HttpPost, ActionName("Delete")]
        [ValidateAntiForgeryToken]
        public ActionResult DeleteConfirmed(int id)
        {
            Student student = db.Students.Find(id);
            db.Students.Remove(student);
            db.SaveChanges();
            return RedirectToAction("Index");
        }

        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                db.Dispose();
            }
            base.Dispose(disposing);
        }
    }
}

感谢到目前为止的建议我现在有一个页面返回。但是，没有加载任何数据。这是一张照片

以下是视图的代码

@model ContosoUniversity.Models.Student

    @{
        ViewBag.Title = "Grab";
    }

    <h2>Grab</h2>

    <p>
        @Html.ActionLink("Create New", "Create")
    </p>
    <table class="table">
        <tr>
            <th>
                @Html.DisplayNameFor(model => model.LastName)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.FirstMidName)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.EnrollmentDate)
            </th>
            <th></th>
        </tr>

    </table>

Answer 1

你的问题是路由。当您请求http://localhost:49706/Student/Grab/{LastName}时，参数studentName正在解析为null，因此您的BadRequestResponse。

您的网址中的模式与默认的ASP.NET MVC路由模式匹配，但它将无法绑定参数的值，因此MVC将正确命中控制器并执行操作，但参数将为null。

您有几个选择：

映射路线

您可以将其添加到路由配置文件：RouteConfig.cs目录中的App_Start：

//Add your own route
routes.MapRoute(
    name: null,
    url: "{controller}/{action}/{studentName}",
    defaults: new { controller = "Student", action = "Grab", id = UrlParameter.Optional }
);

此调用应在调用映射默认路由之前进行。现在，您将能够从路径数据中获取studentName参数的值。

更改网址

您可以通过请求将您的页面添加为新路线来调用相同的操作：

http://localhost:49706/Student/Grab?studentName={LastName}

这里将有效地处理参数。

关于从数据库中提取学生，如果只想匹配完整的姓氏，我会在操作中使用此代码：

public ActionResult Grab(string studentName)
{
    if (studentName == null)
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);

    var student = db.Students.FirstOrDefault(x => x.LastName.ToLower() == studentName.ToLower());
    if (student == null)
        return HttpNotFound();

    return View(student);
}

让我知道它对你有用。

希望这有帮助！

Answer 2

你的第一个错误：

db.Students.Find(studentName); // This one expects an student object not string

所以你需要使用Where linq扩展名，这样你就可以用这样的姓氏过滤你的学生表：

Student student = db.Students.Where(student => student.LastName.Contains(studentName)).FirstOrDefault(); // Im using contains instead of equals to match substrings

Answer 3

我假设你是从Index视图中尝试这样做的。所以因为你的Grab ActionResult期待一个名为studentName的参数（可能想要重命名为与lastName对应的内容）出于可维护性的目的）.. Index视图上的操作链接需要如下所示：

@Html.ActionLink("Details by Last Name", "Grab", "Student", new{studentName = item.LastName}, null)
// I assume `item` because if it's in your Index view you are looping to get each user in their own row..

既然你明白使用一个人的姓是一个坏主意，因为它不是唯一的...但在这个例子中它是..没有必要使用.Contain()方法..你正在寻找一个人，因此您应该使用.SingleOrDefault()。

public ActionResult Grab(string studentName)
{
    // in my experience.. when you're checking a string variable to see if 
    // it is null.. use string.IsNullOrWhiteSpace.. because even though what
    // you're using checks for null.. it doesn't check for white space..


    if(studentName == null) // so change this to if(string.IsNullOrWhiteSpace(studentName))
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);

    Student student = db.Students.SingleOrDefault(student => student.LastName.ToLower() == studentName.ToLower()); // convert the comparison strings to all lower case.. hence the the `.ToLower()` methods for more reliable comparison

    if (student == null)
        return HttpNotFound();

    return View(student);
}

希望这有帮助。

ASP .Net MVC Contoso University如何根据姓氏获取学生详细信息

3 个答案: