ASP.NET Core MVC 打造一个简单的图书馆管理系统 (修正版)（四）图书信息的增删改查

前言：

本系列文章主要为我之前所学知识的一次微小的实践，以我学校图书馆管理系统为雏形所作。

本系列文章主要参考资料：

微软文档：https://docs.microsoft.com/zh-cn/aspnet/core/getting-started/?view=aspnetcore-2.1&tabs=windows

《Pro ASP.NET MVC 5》、《锋利的 jQuery》

此系列皆使用 VS2017+C# 作为开发环境。如果有什么问题或者意见欢迎在留言区进行留言。

项目 github 地址：https://github.com/NanaseRuri/LibraryDemo

本章内容：分页、自定义 HtmlHelper、通过模态窗口确认是否提交表单、上传文件、获取文件、预览文件、select 元素、表单提交数组、checkbox、js 确认关闭页面

注：在对 EF 中的数据进行更改时，需要调用对应 Context 的 SaveChange 方法才能对更改进行保存。

一、视图分页视图模型

首先创建一个视图模型用于确定每页的书籍数、页数

 1     public class PagingInfo
 2     {
 3         public int TotalItems { get; set; }
 4         public int ItemsPerPage { get; set; }
 5         public int CurrentPage { get; set; }
 6 
 7         public int TotalPages
 8         {
 9             get => (int)Math.Ceiling((decimal)TotalItems / ItemsPerPage);
10         }
11     }

然后创建另一个视图模型用于确定该分页信息以及各分页的书籍：

1      public class BookListViewModel
2      {
3          public IEnumerable<BookDetails> BookDetails { get; set; }
4          public PagingInfo PagingInfo { get; set; }
5      }

创建一个自定义 HtmlHelper 用于在视图中使用 Razor 语法获取分页，在 ASP.NET Core 中 TagBuilder 继承自 IHtmlContent，不能直接对 TagBuilder 进行赋值，需调用 MergeAttribute 方法和 InnerHtml 属性的 AppendHtml 方法编写标签；并且 TagBuilder 没有实现 ToString 方法，只能通过其 WriteTo 方法将内容写到一个 TextWriter 对象中以取出其值：

 1     public static class PagingHelper
 2     {
 3         public static HtmlString PageLinks(this IHtmlHelper html, PagingInfo pagingInfo, Func<int, string> pageUrl)
 4         {
 5             StringWriter writer=new StringWriter();
 6             for (int i = 1; i <= pagingInfo.TotalPages; i++)
 7             {
 8                 TagBuilder tag=new TagBuilder("a");
 9                 tag.MergeAttribute("href",pageUrl(i));
10                 tag.InnerHtml.AppendHtml(i.ToString());
11                 if (i==pagingInfo.CurrentPage)
12                 {
13                     tag.AddCssClass("selected");
14                     tag.AddCssClass("btn-primary");
15                 }
16                 tag.AddCssClass("btn btn-default");
17                 tag.WriteTo(writer,HtmlEncoder.Default);
18             }
19             return new HtmlString(writer.ToString());
20         }
21     }

二、编辑图书信息页面的首页

在此准备使用 Session 更快地获取图书信息，为了在使用时更直观，此处对 Session 类进行扩展：

 1     public static class SessionExtensions
 2     {
 3         public static void Set<T>(this ISession session, string key, T value)
 4         {
 5             session.SetString(key, JsonConvert.SerializeObject(value));
 6         }
 7 
 8         public static T Get<T>(this ISession session, string key)
 9         {
10             var value = session.GetString(key);
11             return value == null ? default(T) : JsonConvert.DeserializeObject<T>(value);
12         }
13     }

创建一个 BookInfo 控制器:

1    public class BookInfoController : Controller
2     {
3         private LendingInfoDbContext _lendingInfoDbContext;
4 
5         public BookInfoController(LendingInfoDbContext context)
6         {
7             _lendingInfoDbContext = context;
8         }
9     }

创建学生浏览的首页：

在此使用 Session 获取书籍列表：

创建 BookInfo 控制器并确定其中每个分页的书籍数，使用 Session 获取更快地获取书籍信息：

 1     public class BookInfoController : Controller
 2     {
 3         private LendingInfoDbContext _context;
 4         private static int amout = 4;
 5 
 6         public BookInfoController(LendingInfoDbContext context)
 7         {
 8             _context = context;
 9         }
10 
11         public IActionResult Index(string category, int page = 1)
12         {
13             IEnumerable<BookDetails> books = null;
14             if (HttpContext.Session != null)
15             {
16                 books = HttpContext.Session.Get<IEnumerable<BookDetails>>("bookDetails");
17             }
18             if (books == null)
19             {
20                 books = _context.BooksDetail;
21                 HttpContext.Session?.Set<IEnumerable<BookDetails>>("books", books);
22             }
23             BookListViewModel model = new BookListViewModel()
24             {
25                 PagingInfo = new PagingInfo()
26                 {
27                     ItemsPerPage = amout,
28                     TotalItems = books.Count(),
29                     CurrentPage = page,
30                 },
31                 BookDetails = books.OrderBy(b => b.FetchBookNumber).Skip((page - 1) * amout).Take(amout)
32             };            
33             return View(model);
34         }
35 
36         public FileContentResult GetImage(string isbn)
37         {
38             BookDetails target = _context.BooksDetail.FirstOrDefault(b => b.ISBN == isbn);
39             if (target != null)
40             {
41                 return File(target.ImageData, target.ImageMimeType);
42             }
43             return null;
44         }
45     }

视图页面：

33 行利用 BookListViewModel 中 PagingInfo 的 CurrentPage 获取各序号，32 行中使 img 元素的 src 指向 BookInfoController 的 GetImage 方法以获取图片：

 1 @using LibraryDemo.HtmlHelpers
 2 @model BookListViewModel
 3 @{
 4     ViewData["Title"] = "Index";
 5     int i = 1;
 6     Layout = "_LendingLayout";
 7 }
 8 <style type="text/css">
 9     tr > td {
10         padding: 5px;
11         padding-left: 20px;
12     }
13     tr+tr {
14         border-top: thin solid black;
15         padding-top: 10px;
16     }
17 </style>
18 
19 <hr />
20 <table>
21     <tbody>
22     @foreach (var book in Model.BookDetails)
23     {
24         <tr>
25             <td style=" 3%">@((@Model.PagingInfo.CurrentPage-1)*4+i++)</td>
26             <td style="text-align: center;  150px; height: 200px;">
27                 @if (book.ImageData == null)
28                 {
29                     <label>No Image</label>
30                 }
31                 else
32                 {
33                     <img class="img-thumbnail pull-left" src="@Url.Action("GetImage", "BookInfo", new {book.ISBN})" />
34                 }   
35             </td>
36             <td style="text-align: left;">
37                 <a style="margin-left: 1em;" href="@Url.Action("Detail",new{isbn=@book.ISBN})">@book.Name</a>
38                 <div style="margin-left: 2em;margin-top: 5px">
39                     <span>@book.Author</span>
40                     <br />
41                     <span>@book.Press</span>
42                     <p>@book.FetchBookNumber</p>
43                 </div>
44                 <div style="text-indent: 2em">
45                     <p>@book.Description</p>
46                 </div>
47             </td>
48         </tr>
49     }
50     </tbody>    
51 </table>    
52 <div class="btn-group pull-right">
53     @Html.PageLinks(Model.PagingInfo, x => Url.Action("Index", new { page = x}))
54 </div>

在此同样使用 Session 获取书籍列表：

利用 [Authorize] 特性指定 Role 属性确保只有 Admin 身份的人才能访问该页面：

 1         [Authorize(Roles = "Admin")]
 2         public IActionResult BookDetails(string isbn, int page = 1)
 3         {
 4             IEnumerable<BookDetails> books = null;
 5             BookListViewModel model;
 6             if (HttpContext.Session != null)
 7             {
 8                 books = HttpContext.Session.Get<IEnumerable<BookDetails>>("bookDetails");
 9             }
10             if (books == null)
11             {
12                 books = _context.BooksDetail.AsNoTracking();
13                 HttpContext.Session?.Set<IEnumerable<BookDetails>>("books", books);
14 
15             }
16             if (isbn != null)
17             {
18                 model = new BookListViewModel()
19                 {
20                     BookDetails = new List<BookDetails>() { books.FirstOrDefault(b => b.ISBN == isbn) },
21                     PagingInfo = new PagingInfo()
22                 };
23                 return View(model);
24             }
25             model = new BookListViewModel()
26             {
27 
28                 PagingInfo = new PagingInfo()
29                 {
30                     ItemsPerPage = amout,
31                     TotalItems = books.Count(),
32                     CurrentPage = page,
33                 },
34                 BookDetails = books.OrderBy(b => b.FetchBookNumber).Skip((page - 1) * amout).Take(amout)
35             };
36             return View(model);
37         }

BookDetails 视图，confirmDelete 为删除按钮添加了确认的模态窗口；

53 行为 glyphicon 为 Bootstrap 提供的免费图标，只能通过 span 元素使用：

 1     @using LibraryDemo.HtmlHelpers
 2     @model BookListViewModel
 3     @{
 4         ViewData["Title"] = "BookDetails";
 5         int i = 1;
 6     }
 7 
 8     <script>
 9         function confirmDelete() {
10             var isbns = document.getElementsByName("isbns");
11             var message="确认删除";
12             for (i in isbns) {
13                 if (isbns[i].checked) {
14                     var book = isbns[i].parentElement.nextElementSibling.nextElementSibling.firstElementChild.innerHTML;
15                     message=message+"《"+book+"》";
16                 }
17             }
18             message = message + "?";
19             if (confirm(message) == true) {
20                 return true;
21             } else {
22                 return false;
23             }
24         }
25     </script>
26 
27     <style type="text/css">
28         tr + tr {
29             border-top: thin solid gray;
30         }
31 
32         .container {
33              1200px;
34         }
35     </style>
36 
37 
38     <hr />
39     @if (TempData["message"] != null)
40     {
41         <p>@TempData["message"]</p>
42         <br />
43         <br />
44     }
45     <form class="pull-left" action="@Url.Action("Search")">
46         @Html.DropDownList("keyword",new List<SelectListItem>()
47         {
48             new SelectListItem("书名","Name"),
49             new SelectListItem("ISBN","ISBN"),
50             new SelectListItem("索书号","FetchBookNumber"),
51         })
52         <input type="text" name="value"/>
53         <button type="submit"><span class="glyphicon glyphicon-search"></span></button>
54     </form>
55     <br />
56     <br />
57 
58     <form method="post" asp-action="RemoveBooksAndBookDetails">
59         <table width="1000">
60             <tbody>
61             <tr>
62                 <th></th>
63                 <th >序号</th>
64                 <th>标题</th>
65                 <th ></th>
66                 <th style="text-align: right">ISBN</th>            
67             </tr>
68             @foreach (var book in Model.BookDetails)
69             {
70                 <tr>
71                     <td><input type="checkbox" name="isbns" value="@book.ISBN" /></td>
72                     <td style=" padding-left: 10px">@((Model.PagingInfo.CurrentPage-1)*4+i++)</td>
73                     <td><a asp-action="EditBookDetails" asp-route-isbn="@book.ISBN">@book.Name</a></td>
74                     <td></td>
75                     <td style="text-align: right;">@book.ISBN</td>                
76                 </tr>
77             }
78             </tbody>
79         </table>
80         <br/>
81         <div>
82             <a class="btn btn-primary" href="@Url.Action("AddBookDetails")">添加书籍</a>
83             <button type="submit" class="btn btn-danger" onclick="return confirmDelete()"> 删除书籍</button>        
84         </div>
85     </form>
86 
87     <br />
88     <div class="btn-group pull-right">
89         @Html.PageLinks(Model.PagingInfo, x => Url.Action("BookDetails", new { page = x }))
90     </div>

Index 页面：

BookDetails 页面：

三、添加书籍信息

在此为了接受图片需要使用 IFormFile 接口，为了使图片以原有的格式在浏览器中显示，需要用另一个字段 ImageType 保存文件的格式；

39 页使用 TempData 传递一次性信息告知书籍添加成功，在传递完成后 TempData 将被立即释放：

 1         [Authorize(Roles = "Admin")]
 2         public IActionResult AddBookDetails(BookDetails model)
 3         {
 4             if (model == null)
 5             {
 6                 model = new BookDetails();
 7             }
 8             return View(model);
 9         }
10 
11         [HttpPost]
12         [ValidateAntiForgeryToken]
13         [Authorize(Roles = "Admin")]
14         public async Task<IActionResult> AddBookDetails(BookDetails model, IFormFile image)
15         {
16             BookDetails bookDetails = new BookDetails();
17             if (ModelState.IsValid)
18             {
19                 if (image != null)
20                 {
21                     bookDetails.ImageMimeType = image.ContentType;
22                     bookDetails.ImageData = new byte[image.Length];
23                     await image.OpenReadStream().ReadAsync(bookDetails.ImageData, 0, (int)image.Length);
24                 }
25 
26                 bookDetails.ISBN = model.ISBN;
27                 bookDetails.Name = model.Name;
28                 bookDetails.Author = model.Author;
29                 bookDetails.Description = model.Description;
30                 bookDetails.FetchBookNumber = model.FetchBookNumber;
31                 bookDetails.Press = model.Press;
32                 bookDetails.PublishDateTime = model.PublishDateTime;
33                 bookDetails.SoundCassettes = model.SoundCassettes;
34                 bookDetails.Version = model.Version;
35 
36                 await _lendingInfoDbContext.BooksDetail.AddAsync(bookDetails);
37 
38                 _lendingInfoDbContext.SaveChanges();
39                 TempData["message"] = $"已添加书籍《{model.Name}》";
40                 return RedirectToAction("EditBookDetails");
41             }
42             return View(model);
43         }

AddBookDetails 视图：

为了使表单可以上传文件，需要指定表单的 enctype 属性值为 multipart/form-data，66 行中使用一个 a 元素包含用来上传文件的 input ，指定其 class 为 btn 以生成一个按钮，指定 href="javascript:;" 使该元素不会返回任何值。

指定 input 的 name 属性为 image 以在上传表单时进行模型绑定，指定其 accept 属性令其打开文件选择框时只接收图片。

JS 代码为 input 添加 onchange 事件以预览上传的图片，并为关闭或刷新页面时添加模态窗口进行确认，同时为提交按钮添加事件以重置 window.onbeforeunload 事件从而不弹出确认窗口：

 1 @model LibraryDemo.Models.DomainModels.BookDetails
 2 @{
 3     ViewData["Title"] = "AddBookDetails";
 4 }
 5 
 6 <script>
 7     function preview(file) {
 8         $(".image").addClass("hidden");
 9         $('.preview').wrap("<div></div>");
10         $(".preview").removeClass("hidden");
11         if (file.files && file.files[0]) {
12             var reader = new FileReader();
13             reader.onload = function (evt) {
14                 $('.preview').attr('src', evt.target.result);
15             }
16             reader.readAsDataURL(file.files[0]);
17         } else {
18             $('.preview').attr('src', file.value);
19         }
20     }        
21     window.onbeforeunload = function () {
22         return "您的数据未保存，确定退出？";
23     }
24     function removeOnbeforeunload() {
25         window.onbeforeunload = "";
26     }
27 </script>
28 
29 <h2>添加书籍</h2>
30 
31 <form enctype="multipart/form-data" method="post">
32     <div class="panel-body">
33         <div class="form-group">
34             @Html.LabelFor(m => m.ISBN)
35             @Html.TextBoxFor(m => m.ISBN, new { @class = "form-control" })
36         </div>
37         <div class="form-group">
38             @Html.LabelFor(m => m.Name)
39             @Html.TextBoxFor(m => m.Name, new { @class = "form-control" })
40         </div>
41         <div class="form-group">
42             @Html.LabelFor(m => m.Author)
43             @Html.TextBoxFor(m => m.Author, new { @class = "form-control" })
44         </div>
45         <div class="form-group">
46             @Html.LabelFor(m => m.Press)
47             @Html.TextBoxFor(m => m.Press, new { @class = "form-control" })
48         </div>
49         <div class="form-group">
50             @Html.LabelFor(m => m.FetchBookNumber)
51             @Html.TextBoxFor(m => m.FetchBookNumber, new { @class = "form-control" })
52         </div>
53         <div class="form-group">
54             @Html.LabelFor(m => m.SoundCassettes)
55             @Html.TextBoxFor(m => m.SoundCassettes, new { @class = "form-control" })
56         </div>
57         <div class="form-group">
58             @Html.LabelFor(m => m.Description)
59             @Html.TextAreaFor(m => m.Description, new { @class = "form-control", rows = 5 })
60         </div>
61         <div class="form-group">
62             @Html.LabelFor(m => m.PublishDateTime)
63             <div>@Html.EditorFor(m => m.PublishDateTime)</div>
64         </div>
65         <div class="form-group">
66             @Html.LabelFor(m => m.Version)
67             <div>@Html.EditorFor(m => m.Version)</div>
68         </div>
69         <div class="form-group">
70             <div style="position: relative;">
71                 <label>Image</label>
72                 <a class="btn" href="javascript:;">
73                     选择图片
74                     <input type="file" name="Image" size="40" accept="image/*"
75                            style="position: absolute; z-index: 2; top: 0; left: 0; filter: alpha(opacity=0); opacity: 0; background-color: transparent; color: transparent"
76                            onchange="preview(this)" />
77                 </a>
78                 <img style=" 150px;" class="hidden preview img-thumbnail">
79             </div>
80         </div>        
81         <input type="submit" onclick="removeOnbeforeunload()"/>
82     </div>
83 </form>

结果：

四、删除书籍信息

删除书籍的动作方法：

此处通过在之前的 BookDetails 视图中指定 input 元素的 type 为 checkbox，指定 name 为 isbns 以实现多个字符串的模型绑定：

 1         [Authorize(Roles = "Admin")]
 2         [HttpPost]
 3         [ValidateAntiForgeryToken]
 4         public async Task<IActionResult> RemoveBooksAndBookDetails(IEnumerable<string> isbns)
 5         {
 6             StringBuilder sb = new StringBuilder();
 7             foreach (var isbn in isbns)
 8             {
 9                 BookDetails bookDetails = _lendingInfoDbContext.BooksDetail.First(b => b.ISBN == isbn);
10                 IQueryable<Book> books = _lendingInfoDbContext.Books.Where(b => b.ISBN == isbn);
11                 _lendingInfoDbContext.BooksDetail.Remove(bookDetails);
12                 _lendingInfoDbContext.Books.RemoveRange(books);
13                 sb.Append("《" + bookDetails.Name + "》");
14                 await _lendingInfoDbContext.SaveChangesAsync();
15             }
16             TempData["message"] = $"已移除书籍{sb.ToString()}";
17             return RedirectToAction("BookDetails");
18         }

结果：

五、编辑书籍信息

动作方法：

 1         [Authorize(Roles = "Admin")]
 2         public async Task<IActionResult> EditBookDetails(string isbn)
 3         {
 4             BookDetails book = await _lendingInfoDbContext.BooksDetail.FirstOrDefaultAsync(b => b.ISBN == isbn);
 5             if (book != null)
 6             {
 7                 return View(book);
 8             }
 9             else
10             {
11                 return RedirectToAction("BookDetails");
12             }
13         }
14 
15         [HttpPost]
16         [ValidateAntiForgeryToken]
17         [Authorize(Roles = "Admin")]
18         public async Task<ActionResult> EditBookDetails(BookDetails model, IFormFile image)
19         {
20             BookDetails bookDetails = _lendingInfoDbContext.BooksDetail.FirstOrDefault(b => b.ISBN == model.ISBN);
21             if (ModelState.IsValid)
22             {
23                 if (bookDetails != null)
24                 {
25                     if (image != null)
26                     {
27                         bookDetails.ImageMimeType = image.ContentType;
28                         bookDetails.ImageData = new byte[image.Length];
29                         await image.OpenReadStream().ReadAsync(bookDetails.ImageData, 0, (int)image.Length);
30                     }
31 
32                     BookDetails newBookDetails = model;
33 
34                     bookDetails.Name = newBookDetails.Name;
35                     bookDetails.Author = newBookDetails.Author;
36                     bookDetails.Description = newBookDetails.Description;
37                     bookDetails.FetchBookNumber = newBookDetails.FetchBookNumber;
38                     bookDetails.Press = newBookDetails.Press;
39                     bookDetails.PublishDateTime = newBookDetails.PublishDateTime;
40                     bookDetails.SoundCassettes = newBookDetails.SoundCassettes;
41                     bookDetails.Version = newBookDetails.Version;
42 
43                     await _lendingInfoDbContext.SaveChangesAsync();
44                     TempData["message"] = $"《{newBookDetails.Name}》修改成功";
45                     return RedirectToAction("EditBookDetails");
46                 }
47             }
48             return View(model);
49         }

此处视图与之前 AddBookDetails 大致相同，但在此对一些视图中的 ISBN 字段添加了 readonly 属性使它们不能被直接编辑：

  1 @model LibraryDemo.Models.DomainModels.BookDetails
  2 
  3 @{
  4     ViewData["Title"] = "EditBookDetails";
  5 }
  6 
  7 <script>
  8     function preview(file) {
  9         $(".image").addClass("hidden");
 10         $('.preview').wrap("<div></div>");
 11         $(".preview").removeClass("hidden");
 12         if (file.files && file.files[0]){  
 13             var reader = new FileReader();  
 14             reader.onload = function(evt){
 15                 $('.preview').attr('src' , evt.target.result);
 16             }    
 17             reader.readAsDataURL(file.files[0]);  
 18         }else{  
 19             $('.preview').attr('src' , file.value);
 20         }
 21     }
 22     window.onload = function() {
 23         $("div>input").addClass("form-control");
 24         var isbn = document.getElementById("ISBN");
 25         isbn.setAttribute("readonly","true");
 26     }
 27     window.onbeforeunload = function (event) {
 28         return "您的数据未保存，确定退出？";
 29     }
 30     function removeOnbeforeunload() {
 31         window.onbeforeunload = "";
 32     }
 33 </script>
 34 
 35 <h2>编辑书籍</h2>
 36 
 37 @section Scripts
 38 {
 39     
 40 }
 41 
 42 <form enctype="multipart/form-data" method="post">
 43     <div class="panel-body">
 44         <div class="form-group">
 45             @Html.LabelFor(m => m.ISBN)
 46             @Html.EditorFor(m => m.ISBN)
 47         </div>
 48         <div class="form-group">
 49             @Html.LabelFor(m => m.Name)
 50             @Html.TextBoxFor(m => m.Name, new {@class = "form-control"})
 51         </div>
 52         <div class="form-group">
 53             @Html.LabelFor(m => m.Author)
 54             @Html.TextBoxFor(m => m.Author, new {@class = "form-control"})
 55         </div>
 56         <div class="form-group">
 57             @Html.LabelFor(m => m.Press)
 58             @Html.TextBoxFor(m => m.Press, new {@class = "form-control"})
 59         </div>
 60         <div class="form-group">
 61             @Html.LabelFor(m => m.FetchBookNumber)
 62             @Html.TextBoxFor(m => m.FetchBookNumber, new {@class = "form-control"})
 63         </div>
 64         <div class="form-group">
 65             @Html.LabelFor(m => m.SoundCassettes)
 66             @Html.TextBoxFor(m => m.SoundCassettes, new {@class = "form-control"})
 67         </div>
 68         <div class="form-group">
 69             @Html.LabelFor(m => m.Description)
 70             @Html.TextAreaFor(m => m.Description, new {@class = "form-control", rows = 5})
 71         </div>
 72         <div class="form-group">
 73             @Html.LabelFor(m => m.PublishDateTime)
 74             <div>@Html.EditorFor(m => m.PublishDateTime)</div>
 75         </div>
 76         <div class="form-group">
 77             @Html.LabelFor(m => m.Version)
 78             <div>@Html.EditorFor(m => m.Version)</div>
 79         </div>
 80         <div class="form-group">
 81             <div style="position: relative;">
 82                 <label>Image</label>
 83                 <a class="btn" href="javascript:;">
 84                     选择图片
 85                     <input type="file" name="Image" size="40" accept="image/*"
 86                            style="position: absolute; z-index: 2; top: 0; left: 0; filter: alpha(opacity=0); opacity: 0; background-color: transparent; color: transparent"
 87                            onchange="preview(this)" />
 88                 </a>
 89                 <img style=" 150px;" class="hidden preview img-thumbnail">
 90             </div>
 91             @if (Model.ImageData == null)
 92             {
 93             <div class="form-control-static image">No Image</div>
 94             }
 95             else
 96             {
 97             <img class="img-thumbnail image" style=" 150px;" src="@Url.Action("GetImage", "BookInfo", new {Model.ISBN})" />
 98             }
 99         </div>
100         <br />
101         <a class="btn btn-primary" asp-action="Books" asp-route-isbn="@Model.ISBN" onclick="return removeOnbeforeunload()">编辑外借书籍信息</a>
102         <br />
103         <br />
104         <input type="submit" class="btn btn-success" onclick="return removeOnbeforeunload()"/>
105     </div>
106 </form>

结果：

六、查询特定书籍

此处和之前的账号登录处一样使用 switch 对不同的关键词进行检索：

 1         public async Task<IActionResult> Search(string keyWord, string value)
 2         {
 3             BookDetails bookDetails = new BookDetails();
 4             switch (keyWord)
 5             {
 6                 case "Name":
 7                     bookDetails =await _context.BooksDetail.FirstOrDefaultAsync(b => b.Name == value);
 8                     break;
 9                 case "ISBN":
10                     bookDetails =await _context.BooksDetail.FirstOrDefaultAsync(b => b.ISBN == value);
11                     break;
12                 case "FetchBookNumber":
13                     bookDetails =await _context.BooksDetail.FirstOrDefaultAsync(b => b.FetchBookNumber == value);
14                     break;
15             }
16 
17             if (bookDetails!=null)
18             {
19                 return RedirectToAction("EditBookDetails", new {isbn = bookDetails.ISBN});
20             }
21 
22             TempData["message"] = "找不到该书籍";
23             return RedirectToAction("BookDetails");
24         }

结果：