.net MVC understanding

.net MVC The understanding of the   One 、ASP.Net Two kinds of development mode of the Internet 1.1 ASP.Net WebForm Development model （1） Processing flow In traditional WebForm In mode , We ask for an example http://www.aspnetmvc.com/blog/index.aspx Of URL, So our WebForm The program will go to the root directory of the website to find blog In the catalog index.aspx file , Then from index.aspx Page CodeBehind file (.CS file ) Do logical processing , It may also include fetching data from the database ( What happened BLL To DAL Let's not talk about it here ), And then by index.aspx Page to present to the user . in summary , stay WebForm In mode ： One URL The request is between the server and the URL The physical file on the corresponding path (ASPX Documents or other ), Then the file will process the request and return the result to the client . （2） The development way • Server side control • General handler +Html Static page +Ajax • General handler +Html template engine   1.2 ASP.Net MVC Development model （1） Processing flow stay ASP.Net MVC in , What the client requested URL Is mapped to the corresponding Controller Go to , Then from Controller To handle the business logic , Maybe from Model Take data from , And then by Controller Choose the right one View Return to the client . Let's go back to the previous operation ASP.NET MVC Program access http://www.aspnetmvc.com/Home/Index This URL, It actually accesses HomeController Medium Index This Action. （2） Salient features • 2009 The first open source project version was released in , It's gone 5 year , The development is gradually improved • More concise , Closer to the original “ request - Handle - Respond to ” • More developed 、 More new features 、 The community is active • It will not replace WebForm • Bottom with WebForm It's all the same , It's just different treatment on the pipeline   Two 、MVC Two different interpretations of the model MVC There are two ways to understand patterns ： One is Performance mode , The other is Architecture mode . It divides the application into three main components, namely ： View （View）、 controller （Controller） And models （Model）. Now? , Let's see M-V-C What do they stand for ？ M：Model It's mainly a component that stores or processes data ;Model In fact, it is to realize the operation of the business logic layer on the corresponding database of entity classes , Such as ：CRUD. It includes data 、 Validation rule 、 Application information such as data access and business logic .（ Add ：ViewModel： Model view ） V：View It is a user interface layer component . Mainly is to Model The data in is displayed to the user .aspx and ascx Files are used to handle the responsibilities of views ; C： Controller Dealing with user interaction , from Model Get data in and transfer the data to the designated View; （1）MVC As an understanding of architectural patterns As an architectural pattern ,View Is responsible for displaying data , and Controller Is responsible for obtaining View Transmitted data , Then call the business logic layer to process the completed data and transfer it to View To display . and Model Then deal with business logic , And return the result to Controller. From the perspective of traditional three-tier architecture ,View and Controller All belong to UI layer , and Model Then across BLL And DAL layer . （2）MVC Understanding as a mode of expression （3）MVC Architecture pattern integrated model It can be seen that , about MVC The difference between the two different understandings of Model On the understanding of ： take Model As a business model （BLL、DAL etc. ） Or as a view model （ViewModel）. 3、 ... and 、WebForm vs MVC （1）WebForm advantage : 1. Provides a large number of server-side controls , It can be developed quickly ; 2.ViewState It is convenient to return data ; 3. The cost of learning is low ; shortcoming : 1. The encapsulation is too strong , Although the learning cost is low , Many low-level things are not very clear to beginners ; 2. The custom control is not flexible , It is not conducive to the cooperation between artists and developers , Often those server controls will cause errors if they are handled carelessly ; 3. ViewState The delivery in the page will cause a lot of traffic consumption ; TIP： of WebForm Server controls and ViewState Detailed introduction , Friends who don't know can read another blog post 《ASP.Net WebForm Learning notes ：aspx Explore with server control 》. （2）MVC advantage : 1. It's easy to divide complex applications into Model(ViewModel)、View、Controller Three component model , The processing background logic code is well separated from the foreground display logic , It belongs to loose coupling relationship , In the application of large projects , It is easier for agile development and test driven development , It's very scalable ; 2. Because there are no server-side controls , So the programmer can control it more flexibly , The page is cleaner , No, ViewState; 3. By modifying the routing rules , You can control the generation of custom url, So control generation SEO Amicable URL It will be easier ; 4. Strong type View Realization 、Razor View 、Model Binding mechanism 、Model The verification mechanism of , Safer and more efficient ; shortcoming :  High learning cost , Complicated structure , Unnecessary frequent access to unchanging data , It will also damage operational performance .  Four 、 first ASP.Net MVC Program 4.1 The file organization structure after the new project （1） Create a new one ASP.Net MVC 4 project , choice “ basic ” Configuration and “ASPX” View engine （ Not for the time being Razor engine ）. （2）VS The organization structure of the basic file generated for us is shown in the following figure ： It can be seen that ,VS By default, it helps us create Models、Views as well as Controllers Three folders of , These three folders constitute our ASP.Net MVC Model project . among ,Controllers Is the class file of all controllers , and Models Is the class file of all models , and Views It's all cshtml or aspx File of . 4.2 Controller “ Convention over configuration ” stay Controllers Create a new controller in , named HomeController. In the default Index This Action Create a new view in , The default name is Index that will do . （1）Controller Put it in controllers In the folder , also The naming method is Controller ending （2） Every Controller All corresponding View A folder in , The name of the folder follows Controller Same name （3）Controller The method names in all correspond to a View View （ Not necessary , But it's recommended ） and View Your name and Action The same name （4） The controller must be a non static class , And to achieve IController Interface （5）Controller Types can be put into other projects 4.3 Relevant conventions of views （1） All the views It must be put in Views Under the table of contents （2） The views of different controllers are divided by folders , Each controller corresponds to a view directory （3） General view name and controller name Action Corresponding （ Not necessary ） （4） Multiple controllers The public view is placed in Shared： For example, the common error page 、 List template page 、 Form template page, etc ; 4.4 A bridge for data transmission -ViewData And ViewBag First ,ViewData It's a Key/Value Right dictionary set data structure , Used in Controller and View Build a bridge to transfer data . （1）ViewData yes Controller Properties of , This property is inherited ControllerBase And come . （2）ViewPage There's also one ViewData A property of （3） Controller Action After method execution , return ViewResult, then MVC The framework is executing ExcuteResult When the method is used ,Controller Medium ViewData The data will be passed to ViewPage class , In fact, that is hold Controller Of ViewData Assign a value to ViewPage Page ViewData attribute . （4）ViewBag To transfer data ： We are right. ViewBag Assign values to dynamic attributes of , The value is actually stored in ViewData in , The name of the dynamic attribute is saved as ViewDataDictionary Key , The value of dynamic attribute is saved as ViewDataDictionary Value . PS：ViweBag In fact, it contains one layer Dynamic Of ViewData, What the two brothers share is a container . （5）ViewData And ViewBag Comparison ViewData ViewBag It is Key/Value Dictionary collection It is dynamic Type object from Asp.net MVC 1 And then there is ASP.NET MVC3 Only then be based on Asp.net 3.5 framework be based on Asp.net 4.0 And .net framework ViewData Than ViewBag fast ViewBag Than ViewData slow stay ViewPage When querying data in, you need to convert the appropriate type stay ViewPage No type conversion is required when querying data in There are some type conversion codes Better readability （6） How to use... In programs ViewData And ViewBag ① stay Controller The code in 1 2 3 4 5 6 publicActionResult Index() {      ViewData["Name"] = "Edison Chou";      ViewBag.Name = "Edison Chou";      returnView(); } ② stay View The code in 1 2 3 4 5 6 7 8 9 10 11 12 13 <body>     <div>         <h1>Hi,ASP.Net MVC First Demo!</h1>         <%             for (int i = 0; i < 5; i++)             {                 Response.Write("Hello World!");             }         %>         <p><%: ViewData["Name"] %></p>         <p><%: ViewBag.Name %></p>     </div> </body> 4.5 A preliminary understanding of the routing mechanism We can know through debugging , stay MVC All requests in are attributed to the controller Action. therefore , All requests specify a specific Action,Url The format of is determined according to the routing rules . that , stay ASP.Net MVC What is the default routing rule of , Where was it set up ？ 1 2 3 4 5 6 7 8 9 10 11 12 13 publicclassRouteConfig {         publicstaticvoidRegisterRoutes(RouteCollection routes)         {             routes.IgnoreRoute("{resource}.axd/{*pathInfo}");               routes.MapRoute(                 name: "Default",                 url: "{controller}/{action}/{id}",                 defaults: new{ controller = "Home", action = "Index", id = UrlParameter.Optional }             );         } } open App_Start Folder , Can find RouteConfig This class , see RouteConfig Method of this class , It turns out to be RegisterRoutes This method is for our ASP.Net MVC The project sets the default routing rules ：{controller}/{action}/{id}, That is to say, we can pass http://localhost/Home/Index/1 such URL To access the project . If we want to change the default routing rules , For example, we want to use this URL：http://localhost/Home-Index-1 To access the project , Then directly change the above default routing rule to ：{controller}-{action}-{id} that will do .

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