ASP.NEt MVC5--創建下拉列表 - caofangsheng－IT工程師數位筆記本

文章出處

Adding Search by Genre

If you added the HttpPost version of the Index method, delete it now.

Next, you'll add a feature to let users search for movies by genre. Replace the Index method with the following code:

現在我們來改寫Index方法，

 1   public ActionResult Index(string movieGenre,string searchString)
 2         {
 3             var GenreLst = new List<string>();
 4 
 5             var GenreQry = from d in db.Movies
 6                            orderby d.Genre
 7                            select d.Genre;
 8             GenreLst.AddRange(GenreQry.Distinct());
 9             //SelectList生成列表
10             ViewBag.movieGenre = new SelectList(GenreLst);
11 
12             //Linq查詢
13             var movies = from m in db.Movies select m;
14 
15             if (!string.IsNullOrEmpty(searchString))
16             {
17                 movies = movies.Where(s => s.Title.Contains(searchString));
18             }
19             if (string.IsNullOrEmpty(movieGenre))
20             {
21                 movies = movies.Where(x => x.Genre == movieGenre);
22             }
23             return View(movies);
24 
25            
26         }

  var GenreQry = from d in db.Movies
                            orderby d.Genre
                            select d.Genre;

當執行完這句代碼之后，SQL（GenreQry）為：

1 SELECT    
2 [Extent1].[Genre] AS [Genre]   
3 FROM [dbo].[Movies] AS [Extent1]  
4 ORDER BY [Extent1].[Genre] ASC

var movies = from m in db.Movies select m;

執行完這句代碼之后，SQL（Movies）為：

1 SELECT   
2 [Extent1].[ID] AS [ID],   
3 [Extent1].[Title] AS [Title],    
4 [Extent1].[ReleaseDate] AS [ReleaseDate],   
5 [Extent1].[Genre] AS [Genre],    
6 [Extent1].[Price] AS [Price]  
7 FROM [dbo].[Movies] AS [Extent1]

現在先讓我們，在Index視圖頁面中，添加一個實現下拉框的代碼吧：

In the following code:

@Html.DropDownList("movieGenre", "All")
The parameter "movieGenre" provides the key for the DropDownList helper to find a IEnumerable<SelectListItem > in the  ViewBag. The ViewBag was  populated in the action  method:
這句話的意思是：moviegenre參數，為DropDownList方法，提供了主鍵，去找到在控制器中定義的Viewbag.movieGenre
The parameter "All" provides the item in the list to be preselected. Had we used the following code: 
這句話的意思是：All參數，提供了默認選擇項



效果圖：







In this section you created a search action method and view that let users search  by movie title and genre. In the next section, you'll look at how to add a  property to the Movie model and how to add an initializer that will  automatically create a test database.

通過下拉列表，來搜索：


通過下拉列表和title輸入框搜索：