EF6与mvc5系列（2）:实现基本的增删查改

 1 @model ContosoUniversity.Models.Student
 2 
 3 @{
 4     ViewBag.Title = "Details";
 5 }
 6 
 7 <h2>Details</h2>
 8 
 9 <div>
10     <h4>Student</h4>
11     <hr />
12     <dl class="dl-horizontal">
13         <dt>
14             @Html.DisplayNameFor(model => model.LastName)
15         </dt>
16 
17         <dd>
18             @Html.DisplayFor(model => model.LastName)
19         </dd>
20 
21         <dt>
22             @Html.DisplayNameFor(model => model.FirstMidName)
23         </dt>
24 
25         <dd>
26             @Html.DisplayFor(model => model.FirstMidName)
27         </dd>
28 
29         <dt>
30             @Html.DisplayNameFor(model => model.EnrollmentDate)
31         </dt>
32 
33         <dd>
34             @Html.DisplayFor(model => model.EnrollmentDate)
35         </dd>
36         <dt>
37             @Html.DisplayNameFor(model=>model.Enrollments);
38         </dt>
39         <dd>
40             <table class="table">
41                 <tr>
42                     <th>Course Title</th>
43                     <th>Grade</th>
44                 </tr>
45                 @foreach(var item in Model.Enrollments)
46                 {
47                     <tr>
48                         <td>
49                             @Html.DisplayFor(modelItem=>item.Course.Title)
50                         </td>
51                         <td>
52                             @Html.DisplayFor(modelItem=>item.Grade);
53                         </td>
54                     </tr>
55                 }
56             </table>
57         </dd>
58     </dl>
59 </div>
60 <p>
61     @Html.ActionLink("Edit", "Edit", new { id = Model.ID }) |
62     @Html.ActionLink("Back to List", "Index")
63 </p>

        /// <summary>
        /// 通过模型绑定添加Student实体，asp.net mvc中的模型绑定将post表单
        /// 转为CLR类型，并且将其以参数的形式传递到Action方法
        /// 因为ID字段是主键，所以添加数据的时候ID字段会自动创建。不需要模型绑定
        /// </summary>
        /// <param name="student"></param>
        /// <returns></returns>
        public ActionResult Create([Bind(Include="LastName, FirstMidName, EnrollmentDate")] Student student)
        {
            try
            {
                //服务器端验证，稍后将会看到客户端验证
                if (ModelState.IsValid)
                {
                    db.Students.Add(student);
                    db.SaveChanges();
                    return RedirectToAction("Index");
                }
            }
            catch (DataException)
            {
                ModelState.AddModelError("","创建失败！");
            }
            return View(student);
        }

 [HttpPost,ActionName("Edit")]
        [ValidateAntiForgeryToken]
        public ActionResult EditPost(int ?id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            var studentToUpdate = db.Students.Find(id);
            //调用TryUpdateModel方法修改用户传入的字段，EF会自动跟踪修改 Modified标志，
            if (TryUpdateModel(studentToUpdate,"",new string []{ "LastName", "FirstMidName", "EnrollmentDate"}))
            {
                try
                {
                    //调用此方法后 Modified会调用sql修改数据行，忽略并发冲突，所有的数据都会被修改，包括那些用户没有修改的
                    //稍后将会涉及如何处理并发冲突，如果你指仅修改数据库的个别字段，你可以将实体设置成Unchanged设置个别字段为Modified
                    db.SaveChanges();
                    return RedirectToAction("Index");
                }
                catch (DataException)
                {
                    ModelState.AddModelError("","修改失败");
                }
            }
            return View(studentToUpdate);
        }

// GET: /Student/Delete/5
/// <summary>
        /// 添加可选参数设置为false，在post请求的Delete方法中会调用get方法，如果删除成功状态为true，否则为false
        /// </summary>
        /// <param name="id"></param>
        /// <param name="saveChangesError"></param>
        /// <returns></returns>

        public ActionResult Delete(int? id,bool? saveChangesError=false)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            if (saveChangesError.GetValueOrDefault())
            {
                ViewBag.ErrorMessage = "删除失败！";
            }
            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)
        {
            try
            {
                //视图生成代码
                //Student student = db.Students.Find(id);
                //db.Students.Remove(student);
                //为了提高性能可以使用下面代码避免不需要的sql查询,这涉及到了之前讲过的实体状态
                Student studentToDelete = new Student() {ID=id };
                db.Entry(studentToDelete).State = EntityState.Deleted;
                db.SaveChanges();
            }
            catch (DataException)
            {
                return RedirectToAction("Delete", new { id = id, saveChangesError = true });
            }
            return  RedirectToAction("Index");
        }

<h2>Delete</h2>
<p class="error">@ViewBag.ErrorMessage</p>
<h3>Are you sure you want to delete this?</h3>