ASP.NET Core 打造一個簡單的圖書館管理系統（五）初始化書籍信息

本文轉載自查看原文 2019-01-31 21:30 618 自定義 HtmlHelper/ 分頁/ ASP.NET Core/ 數據庫初始化器/ Session

前言：

本系列文章主要為我之前所學知識的一次微小的實踐，以我學校圖書館管理系統為雛形所作。

本系列文章主要參考資料：

微軟文檔：https://docs.microsoft.com/zh-cn/aspnet/core/getting-started/?view=aspnetcore-2.1&tabs=windows

《Pro ASP.NET MVC 5》、《鋒利的 jQuery》

當此系列文章寫完后會在一周內推出修正版。

此系列皆使用 VS2017+C# 作為開發環境。如果有什么問題或者意見歡迎在留言區進行留言。

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

本章內容：自定義 HtmlHelper、Session 的使用、分頁、數據庫初始化器、取消 int 主鍵自動增長

一、對圖書信息的域模型進行修改

由於在此處我使用了二維碼作為主鍵，一個二維碼不可能同時放在不同的書架上，因此重寫之前建立的多對多的模型。

移除 BookMiddle，去除 Book類中的 ICollection<BookMiddle> 字段，改為 Bookshelf 字段。

 1     public class Book
 2     {                                
 3         /// <summary>
 4         /// 二維碼
 5         /// </summary>
 6         [Key]
 7         public string BarCode { get; set; }
 8 
 9         public string ISBN { get; set; }
10 
11         /// <summary>
12         /// 書名
13         /// </summary>
14         [Required]
15         public string Name { get; set; }         
16 
17         /// <summary>
18         /// 取書號
19         /// </summary>
20         public string FetchBookNumber { get; set; }
21 
22         /// <summary>
23         /// 所在書架
24         /// </summary>
25         //public Bookshelf Bookshelf { get; set; }
26         public Bookshelf Bookshelf { get; set; }
27 
28         /// <summary>
29         /// 借出時間
30         /// </summary>
31         public DateTime? BorrowTime { get; set; }
32 
33         /// <summary>
34         /// 到期時間
35         /// </summary>
36         public DateTime? MatureTime { get; set; } 
37 
38         /// <summary>
39         /// 預約最晚借書日期
40         /// </summary>
41         public DateTime? AppointedLatestTime { get; set; }
42 
43         /// <summary>
44         /// 借閱狀態
45         /// </summary>
46         public BookState State { get; set; }        
47 
48         /// <summary>
49         /// 持有者，指定外鍵
50         /// </summary>
51         public Student Keeper { get; set; }
52     }

View Code

移除 Bookshelf 類中的 ICollection<BookMiddle> 字段，改為 ICollection<Book> 字段

 1     public class Bookshelf
 2     {
 3         /// <summary>
 4         /// 書架ID
 5         /// </summary>
 6         [Key]
 7         public int BookshelfId { get; set; }
 8 
 9         /// <summary>
10         /// 書架的書籍類別
11         /// </summary>
12 
13         [Required]
14         public string Sort { get; set; }               
15         /// <summary>
16         /// 最小取書號
17         /// </summary>
18         [Required]
19         public string MinFetchNumber { get; set; }
20         [Required]
21         public string MaxFetchNumber { get; set; }
22 
23         /// <summary>
24         /// 書架位置
25         /// </summary>
26         [Required]
27         public string Location { get; set; }
28 
29         /// <summary>
30         /// 全部藏書
31         /// </summary>
32         public ICollection<Book> Books { get; set; }
33     }

View Code

為了能夠給書籍添加縮略圖以及更方便的編寫邏輯，為 Book 和 BookDetail 添加多個字段：

 1     /// <summary>
 2     /// 用於借閱的書籍信息
 3     /// </summary>    
 4     public class Book
 5     {                                
 6         /// <summary>
 7         /// 二維碼
 8         /// </summary>
 9         [Key][Required(ErrorMessage = "未填寫二維碼")]
10         [Display(Name = "二維碼")]
11         public string BarCode { get; set; }
12 
13         public string ISBN { get; set; }
14 
15         /// <summary>
16         /// 書名
17         /// </summary>
18         [Required]
19         [Display(Name = "書名")]
20         public string Name { get; set; }
21 
22         /// <summary>
23         /// 取書號
24         /// </summary>
25         [Display(Name = "取書號")]
26         public string FetchBookNumber { get; set; }
27 
28         /// <summary>
29         /// 所在書架
30         /// </summary>
31         public Bookshelf Bookshelf { get; set; }
32 
33         [Display(Name = "書架號")]
34         public int BookshelfId { get; set; }
35 
36         /// <summary>
37         /// 借出時間
38         /// </summary>
39         [Display(Name = "借出時間")]
40         public DateTime? BorrowTime { get; set; }
41 
42         /// <summary>
43         /// 到期時間
44         /// </summary>
45         [Display(Name = "到期時間")]
46         public DateTime? MatureTime { get; set; }
47 
48         /// <summary>
49         /// 預約最晚借書日期
50         /// </summary>
51         [Display(Name = "預約取書時間")]
52         public DateTime? AppointedLatestTime { get; set; }
53 
54         /// <summary>
55         /// 借閱狀態
56         /// </summary>
57         [Display(Name = "書籍狀態")]
58         public BookState State { get; set; }
59 
60         /// <summary>
61         /// 持有者，指定外鍵
62         /// </summary>
63         public Student Keeper { get; set; }
64         [Display(Name = "持有者學號")]
65         public string KeeperId { get; set; }
66 
67         [Display(Name = "位置")]
68         public string Location { get; set; }
69 
70         [Display(Name = "分類")]
71         public string Sort { get; set; }
72     }

 1     /// <summary>
 2     /// 書籍自身的詳細信息
 3     /// </summary>
 4     public class BookDetails
 5     {
 6         [Key]
 7         public string ISBN { get; set; }
 8         [Required]
 9         public string Name { get; set; }
10         [Required]
11         public string Author { get; set; }
12         [Required]
13         public string Press { get; set; }
14         [Required]
15         public string FetchBookNumber { get; set; }       
16         /// <summary>
17         /// 出版時間
18         /// </summary>
19         [Required]
20         public DateTime PublishDateTime{ get; set; }
21 
22         /// <summary>
23         /// 書籍版本
24         /// </summary>
25         [Required]
26         public int Version { get; set; }
27 
28         /// <summary>
29         /// 載體形態，包括頁數、媒介等信息
30         /// </summary>
31         public string SoundCassettes { get; set; }
32 
33         /// <summary>
34         /// 簡介
35         /// </summary>
36         public string Description { get; set; }
37 
38 
39         /// <summary>
40         /// 縮略圖
41         /// </summary>
42         public byte[] ImageData { get; set; }
43         public string ImageMimeType { get; set; }
44     }

由於 EF 會自動將 int 類型的主鍵設置為自動增長，因此自定義 Bookshelf 的 ID 在插入數據庫時會報錯，在此需添加修飾 [DatabaseGenerated(DatabaseGeneratedOption.None)] 告知 ef 取消該設置：

 1     public class Bookshelf
 2     {
 3         /// <summary>
 4         /// 書架ID
 5         /// </summary>
 6         [Key]
 7         //不自動增長
 8  [DatabaseGenerated(DatabaseGeneratedOption.None)] 
 9         public int BookshelfId { get; set; }
10 
11         /// <summary>
12         /// 書架的書籍類別
13         /// </summary>
14 
15         [Required]
16         public string Sort { get; set; }               
17         /// <summary>
18         /// 最小取書號
19         /// </summary>
20         [Required]
21         public string MinFetchNumber { get; set; }
22         [Required]
23         public string MaxFetchNumber { get; set; }
24 
25         /// <summary>
26         /// 書架位置
27         /// </summary>
28         [Required]
29         public string Location { get; set; }
30 
31         /// <summary>
32         /// 全部藏書
33         /// </summary>
34         public ICollection<Book> Books { get; set; }
35     }

然后添加遷移並更新數據庫，若更新失敗在此選擇移除數據庫以及遷移再執行該步驟，生產中應當備份原文件：

1     cd LibraryDemo
2     add-migration RemoveBookMiddle -c LibraryDemo.Data.LendingInfoDbContext
3     update-database -c LibraryDemo.Data.LendingInfoDbContext

新建 BookInitiator 用於初始化該數據庫，在這里會報一個 Book 重復主鍵的錯誤，不知道為什么但是數據確實全都插進去了：

  1 public class BookInitiator
  2     {
  3         public static async Task BookInitial(IServiceProvider serviceProvider)
  4         {
  5             LendingInfoDbContext context = serviceProvider.GetRequiredService<LendingInfoDbContext>();
  6             if (!context.Books.Any() || !context.Bookshelves.Any())
  7             {
  8                 Bookshelf[] bookshelfs = new[]
  9                 {
 10                     new Bookshelf()
 11                     {
 12                         BookshelfId = 1,
 13                         Location = "主校區",
 14                         Sort = "計算機"
 15                     },
 16                     new Bookshelf()
 17                     {
 18                         BookshelfId = 2,
 19                         Location = "主校區",
 20                         Sort = "文學"
 21                     },
 22                     new Bookshelf()
 23                     {
 24                         BookshelfId = 3,
 25                         Location = "東校區",
 26                         Sort = "計算機"
 27                     },
 28                     new Bookshelf()
 29                     {
 30                         BookshelfId = 4,
 31                         Location = "閱覽室",
 32                         Sort = "文學"
 33                     },
 34                     new Bookshelf()
 35                     {
 36                         BookshelfId = 5,
 37                         Location = "閱覽室",
 38                         Sort = "計算機"
 39                     },
 40                 };
 41 
 42                 Book[] books = new[]
 43                 {
 44                     new Book()
 45                     {
 46                         Name = "精通ASP.NET MVC 5",
 47                         BarCode = "001100987211",
 48                         ISBN = "978-7-115-41023-8",
 49                         State = BookState.Normal,
 50                         FetchBookNumber = "TP393.092 19",
 51                         Location = "主校區",
 52                         Sort = "計算機"
 53                     },
 54                     new Book()
 55                     {
 56                         Name = "精通ASP.NET MVC 5",
 57                         BarCode = "001100987212",
 58                         ISBN = "978-7-115-41023-8",
 59                         State = BookState.Normal,
 60                         FetchBookNumber = "TP393.092 19",
 61                         Location = "主校區",
 62                         Sort = "計算機"
 63                     },
 64                     new Book()
 65                     {
 66                         Name = "精通ASP.NET MVC 5",
 67                         BarCode = "001100987213",
 68                         ISBN = "978-7-115-41023-8",
 69                         State = BookState.Normal,
 70                         FetchBookNumber = "TP393.092 19",
 71                         Location = "東校區",
 72                         Sort = "計算機"
 73                     },
 74                     new Book()
 75                     {
 76                         Name = "精通ASP.NET MVC 5",
 77                         BarCode = "001100987214",
 78                         ISBN = "978-7-115-41023-8",
 79                         State = BookState.Readonly,
 80                         FetchBookNumber = "TP393.092 19",
 81                         Location = "閱覽室",
 82                         Sort = "計算機"
 83                     },
 84                     new Book()
 85                     {
 86                         Name = "Entity Framework實用精要",
 87                         BarCode = "001101279682",
 88                         ISBN = "978-7-302-48593-3",
 89                         State = BookState.Normal,
 90                         FetchBookNumber = "TP393.09 447",
 91                         Location = "主校區",
 92                         Sort = "計算機"
 93                     },
 94                     new Book()
 95                     {
 96                         Name = "Entity Framework實用精要",
 97                         BarCode = "001101279683",
 98                         ISBN = "978-7-302-48593-3",
 99                         State = BookState.Normal,
100                         FetchBookNumber = "TP393.09 447",
101                         Location = "主校區",
102                         Sort = "計算機"
103                     },
104                     new Book()
105                     {
106                         Name = "Entity Framework實用精要",
107                         BarCode = "001101279684",
108                         ISBN = "978-7-302-48593-3",
109                         State = BookState.Normal,
110                         FetchBookNumber = "TP393.09 447",
111                         Location = "東校區",
112                         Sort = "計算機"
113                     },
114                     new Book()
115                     {
116                         Name = "Entity Framework實用精要",
117                         BarCode = "001101279685",
118                         ISBN = "978-7-302-48593-3",
119                         State = BookState.Normal,
120                         FetchBookNumber = "TP393.09 447",
121                         Location = "東校區",
122                         Sort = "計算機"
123                     },
124                     new Book()
125                     {
126                         Name = "Entity Framework實用精要",
127                         BarCode = "001101279686",
128                         ISBN = "978-7-302-48593-3",
129                         State = BookState.Normal,
130                         FetchBookNumber = "TP393.09 447",
131                         Location = "閱覽室",
132                         Sort = "計算機"
133                     },
134                     new Book()
135                     {
136                         Name = "Rails 5敏捷開發",
137                         BarCode = "001101290497",
138                         ISBN = "978-7-5680-3659-7",
139                         State = BookState.Normal,
140                         FetchBookNumber = "TP393.09 448",
141                         Location = "主校區",
142                         Sort = "計算機"
143                     },
144                     new Book()
145                     {
146                         Name = "Rails 5敏捷開發",
147                         BarCode = "001101290498",
148                         ISBN = "978-7-5680-3659-7",
149                         State = BookState.Normal,
150                         FetchBookNumber = "TP393.09 448",
151                         Location = "主校區",
152                         Sort = "計算機"
153                     },
154                     new Book()
155                     {
156                         Name = "Rails 5敏捷開發",
157                         BarCode = "001101290499",
158                         ISBN = "978-7-5680-3659-7",
159                         State = BookState.Readonly,
160                         FetchBookNumber = "TP393.09 448",
161                         Location = "主校區",
162                         Sort = "計算機"
163                     },
164                     new Book()
165                     {
166                         Name = "你必須掌握的Entity Framework 6.x與Core 2.0",
167                         BarCode = "001101362986",
168                         ISBN = "978-7-5680-3659-7",
169                         State = BookState.Normal,
170                         FetchBookNumber = "TP393.09 452",
171                         Location = "主校區",
172                         Sort = "計算機"
173                     },
174                     new Book()
175                     {
176                         Name = "你必須掌握的Entity Framework 6.x與Core 2.0",
177                         BarCode = "001101362987",
178                         ISBN = "978-7-5680-3659-7",
179                         State = BookState.Readonly,
180                         FetchBookNumber = "TP393.09 452",
181                         Location = "主校區",
182                         Sort = "計算機"
183                     },
184                     new Book()
185                     {
186                         Name = "毛選. 第一卷",
187                         BarCode = "00929264",
188                         ISBN = "7-01-000922-8",
189                         State = BookState.Normal,
190                         FetchBookNumber = "A41 1:1",
191                         Location = "主校區",
192                         Sort = "文學"
193                     },
194                     new Book()
195                     {
196                         Name = "毛選. 第一卷",
197                         BarCode = "00929265",
198                         ISBN = "7-01-000922-8",
199                         State = BookState.Normal,
200                         FetchBookNumber = "A41 1:1",
201                         Location = "主校區",
202                         Sort = "文學"
203                     },
204                     new Book()
205                     {
206                         Name = "毛選. 第一卷",
207                         BarCode = "00929266",
208                         ISBN = "7-01-000922-8",
209                         State = BookState.Readonly,
210                         FetchBookNumber = "A41 1:1",
211                         Location = "閱覽室",
212                         Sort = "文學"
213                     },
214                     new Book()
215                     {
216                         Name = "毛選. 第二卷",
217                         BarCode = "00929279",
218                         ISBN = "7-01-000915-5",
219                         State = BookState.Normal,
220                         FetchBookNumber = "A41 1:2",
221                         Location = "主校區",
222                         Sort = "文學"
223                     },
224                     new Book()
225                     {
226                         Name = "毛選. 第二卷",
227                         BarCode = "00929280",
228                         ISBN = "7-01-000915-5",
229                         State = BookState.Readonly,
230                         FetchBookNumber = "A41 1:2",
231                         Location = "閱覽室",
232                         Sort = "文學"
233                     },
234                     new Book()
235                     {
236                         Name = "毛選. 第三卷",
237                         BarCode = "00930420",
238                         ISBN = "7-01-000916-3",
239                         State = BookState.Normal,
240                         FetchBookNumber = "A41 1:3",
241                         Location = "主校區",
242                         Sort = "文學"
243                     },
244                     new Book()
245                     {
246                         Name = "毛選. 第三卷",
247                         BarCode = "00930421",
248                         ISBN = "7-01-000916-3",
249                         State = BookState.Readonly,
250                         FetchBookNumber = "A41 1:3",
251                         Location = "閱覽室",
252                         Sort = "文學"
253                     },
254                     new Book()
255                     {
256                         Name = "毛選. 第四卷",
257                         BarCode = "00930465",
258                         ISBN = "7-01-000925-2",
259                         State = BookState.Normal,
260                         FetchBookNumber = "A41 1:4",
261                         Location = "主校區",
262                         Sort = "文學"
263                     },
264                     new Book()
265                     {
266                         Name = "毛選. 第四卷",
267                         BarCode = "00930466",
268                         ISBN = "7-01-000925-2",
269                         State = BookState.Readonly,
270                         FetchBookNumber = "A41 1:4",
271                         Location = "閱覽室",
272                         Sort = "文學"
273                     }
274                 };
275 
276                 BookDetails[] bookDetails = new[]
277                 {
278                     new BookDetails()
279                     {
280                         Author = "Admam Freeman",
281                         Name = "精通ASP.NET MVC 5",
282                         ISBN = "978-7-115-41023-8",
283                         Press = "人民郵電出版社",
284                         PublishDateTime = new DateTime(2016,1,1),
285                         SoundCassettes = "13, 642頁 : 圖 ; 24cm",
286                         Version = 1,
287                         FetchBookNumber = "TP393.092 19",
288                         Description = "ASP.NET MVC 5框架是微軟ASP.NET Web平台的新進展。它提供了高生產率的編程模型，結合ASP.NET的全部優勢，促成更整潔的代碼架構、測試驅動開發和強大的可擴展性。本書涵蓋ASP.NET MVC 5的所有開發優勢技術，包括用C#屬性定義路由技術及重寫過濾器技術等。且構建MVC應用程序的用戶體驗也有本質上的改進。其中書里也專一講解了用新Visual Studio 2013創建MVC應用程序時的技術和技巧。本書包括完整的開發工具介紹以及對代碼進行輔助編譯和調試的技術。本書還涉及流行的Bootstrap JavaScript庫，該庫現已被納入到MVC 5之中，為開發人員提供更廣泛的多平台CSS和HTML5選項，而不必像以前那樣去加載大量的第三方庫。"
289                     },
290                     new BookDetails()
291                     {
292                         Author = "呂高旭",
293                         Name = "Entity Framework實用精要",
294                         ISBN = "978-7-302-48593-3",
295                         Press = "清華大學出版社",
296                         PublishDateTime = new DateTime(2018,1,1),
297                         SoundCassettes = "346頁 ; 26cm",
298                         Version = 1,
299                         FetchBookNumber = "TP393.09 447",
300                         Description = "本書通過介紹Entity Framework與 LINQ 開發實戰的案例，以 Entity Framework 技術內容的討論為主線，結合關鍵的 LINQ技巧說明，提供讀者系統性學習 Entity Framework 所需的內容。本書旨在幫助讀者進入 Entity Framework的世界，建立必要的技術能力，同時希望讀者在完成本書的教學課程之后，能夠更進一步地將其運用在實際的項目開發中。"
301                     },
302                     new BookDetails()
303                     {
304                         Author = "魯比",
305                         Name = "Rails 5敏捷開發",
306                         ISBN = "978-7-5680-3659-7",
307                         Press = "華中科技大學出版社",
308                         PublishDateTime = new DateTime(2018,1,1),
309                         SoundCassettes = "xxi, 451頁 : 圖 ; 23cm",
310                         Version = 1,
311                         FetchBookNumber = "TP393.09 448",
312                         Description = "本書以講解“購書網站”案例為主線, 逐步介紹Rails的內置功能。全書分為3部分, 第一部分介紹Rails的安裝、應用程序驗證、Rails框架的體系結構, 以及Ruby語言知識; 第二部分用迭代方式構建應用程序, 然后依據敏捷開發模式開展測試, 最后用Capistrano完成部署; 第三部分補充日常實用的開發知識。本書既有直觀的示例, 又有深入的分析, 同時涵蓋了Web開發各方面的知識, 堪稱一部內容全面而又深入淺出的佳作。第5版增加了關於Rails 5和Ruby 2.2新特性和最佳實踐的內容。"
313                     },
314                     new BookDetails()
315                     {
316                         Author = "汪鵬",
317                         Name = "你必須掌握的Entity Framework 6.x與Core 2.0",
318                         ISBN = "978-7-302-50017-9",
319                         Press = "清華大學出版社",
320                         PublishDateTime = new DateTime(2018,1,1),
321                         SoundCassettes = "X, 487頁 : 圖 ; 26cm",
322                         Version = 1,
323                         FetchBookNumber = "TP393.09 452",
324                         Description = "本書分為四篇，第一篇講解Entity Framework 6.x的基礎，包括數據庫表的創建，數據的操作和數據加載方式。第二篇講解Entity Framework 6.x進階，包括基本原理和性能優化。第三篇講解跨平台Entity Framework Core 2.x的基礎知識和開發技巧。第四篇講解在Entity Framework Core 2.x中解決並發問題，並給出實戰開發案例。"
325                     },
326                     new BookDetails()
327                     {
328                         Author = "毛",
329                         Name = "毛選. 第一卷",
330                         ISBN = "7-01-000914-7",
331                         Press = "人民出版社",
332                         PublishDateTime = new DateTime(1991,1,1),
333                         SoundCassettes = "340頁 : 肖像 ; 19厘米",
334                         FetchBookNumber = "A41 1:1",
335                         Version = 2,
336                         Description = "《毛選》是對20世紀中國影響最大的書籍之一。"
337                     },
338                     new BookDetails()
339                     {
340                         Author = "毛",
341                         Name = "毛選. 第二卷",
342                         ISBN = "7-01-000915-5",
343                         Press = "人民出版社",
344                         PublishDateTime = new DateTime(1991,1,1),
345                         SoundCassettes = "343-786頁 : 肖像 ; 19厘米",
346                         Version = 2,
347                         FetchBookNumber = "A41 1:2",
348                         Description = "《毛選》是對20世紀中國影響最大的書籍之一。"
349                     },
350                     new BookDetails()
351                     {
352                         Author = "毛",
353                         Name = "毛選. 第三卷",
354                         ISBN = "7-01-000916-3",
355                         Press = "人民出版社",
356                         PublishDateTime = new DateTime(1991,1,1),
357                         SoundCassettes = "789Ł±1120頁 ; 20厘米",
358                         FetchBookNumber = "A41 1:3",
359                         Version = 2,
360                         Description = "《毛選》是對20世紀中國影響最大的書籍之一。"
361                     },
362                     new BookDetails()
363                     {
364                         Author = "毛",
365                         Name = "毛選. 第四卷",
366                         ISBN = "7-01-000925-2",
367                         Press = "人民出版社",
368                         PublishDateTime = new DateTime(1991,1,1),
369                         SoundCassettes = "1123Ł±1517頁 ; 20厘米",
370                         FetchBookNumber = "A41 1:4",
371                         Version = 2,
372                         Description = "《毛選》是對20世紀中國影響最大的書籍之一。"
373                     },
374                 };
375 
376                 var temp = from book in books
377                            from bookshelf in bookshelfs
378                            where book.Location == bookshelf.Location && book.Sort == bookshelf.Sort
379                            select new { BarCode = book.BarCode, BookshelfId = bookshelf.BookshelfId };
380 
381                 foreach (var bookshelf in bookshelfs)
382                 {
383                     bookshelf.Books=new List<Book>();
384                 }
385 
386                 foreach (var tem in temp)
387                 {
388                     Bookshelf targetShelf = bookshelfs.Single(bookshelf => bookshelf.BookshelfId == tem.BookshelfId);
389                     Book targetBook = books.Single(book => book.BarCode == tem.BarCode);
390                     targetShelf.Books.Add(targetBook);
391                 }
392 
393                 foreach (var bookshelf in bookshelfs)
394                 {
395                     bookshelf.MaxFetchNumber=bookshelf.Books.Max(b => b.FetchBookNumber);
396                     bookshelf.MinFetchNumber=bookshelf.Books.Min(b => b.FetchBookNumber);
397                 }
398 
399                 foreach (var bookshelf in bookshelfs)
400                 {
401                     await context.Bookshelves.AddAsync(bookshelf);
402                     await context.SaveChangesAsync();
403                 }
404 
405                 foreach (var bookDetail in bookDetails)
406                 {
407                     await context.BooksDetail.AddAsync(bookDetail);
408                     await context.SaveChangesAsync();
409                 }
410 
411                 foreach (var book in books)
412                 {
413                     await context.Books.AddAsync(book);
414                     await context.SaveChangesAsync();
415                 }
416             }
417         }
418     }

View Code

在 Configure 方法中調用該數據庫初始化方法：

1             BookInitiator.BookInitial(app.ApplicationServices).Wait();

運行后查看數據庫：

二、圖書借閱主頁面

首先創建一個視圖模型用於確定分頁信息：

 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     }

然后創建另一個視圖模型用於確定該分頁信息以及各分頁的書籍：

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

創建一個自定義 HtmlHelper 用於在視圖中使用 Razor 語法獲取分頁，在 ASP.NET Core 中 TagBuilder 繼承自 IHtmlContent，不能直接對 TagBuilder 進行賦值，需調用 MergeAttribute 方法和 InnerHtml 屬性的 AppendHtml 方法編寫標簽；並且 TagBuilder 沒有實現 ToString 方法，只能通過其 WriteTo 方法將內容寫到一個 TextWriter 對象中以取出其值：

 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     }

創建 BookInfo 控制器並確定其中每個分頁的書籍數，使用 Session 獲取更快地獲取書籍信息：

 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     }

視圖頁面：

24 行利用 BookListViewModel 中 PagingInfo 的 CurrentPage 獲取各序號，32 行中使 img 元素的 src 指向 BookInfoController 的 GetImage 方法以獲取圖片：

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

最終結果：

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