11 Getting Started with ASP.NET Beginning ASP.NET in C# and VB Chapters 1 and 2

22 Objectives You will be able to Create a very simple web application in Visual Studio. Dynamically alter contents of a page. Get and process text input from the user. Understand the relationship between what you write in Visual Studio and what the browser receives from the server.

ASP.NET Active Server Pages “Classic” ASP introduced in 1996 VB Script xxx.asp page files. ASP.NET introduced in 2002 xxx.aspx page files. xxx.aspx.cs or xxx.aspx.vb code files. ASP.NET MVC introduced

44 ASP.NET ASP.NET permits us to dynamically create content for a web page using code that runs on the server. File of text similar to HTML. Can include real HTML. We can modify any properties of page elements at run time. Server translates this pseudo-HTML into real HTML which it sends to the browser. We can provide C# or VB code to respond to events such as button clicks.

55 Hello, World! Let’s start with a “Hello, World” ASP.NET application. Get past the startup hurdles before trying to write real web application code. We will use Visual Studio’s built in web server to test and demonstrate our web application code.

66 Creating a New Web App In Visual Studio, File > New Web Site (NOT New project) Web Site vs. Project in Visual Studio.

7 Empty Web Site Web Site Name Check this setting

8 View Solution Explorer

99 The Solution Explorer

10 A New “Empty” Web Site Visual Studio is ambiguous about “project” There is no project file such as you might have seen for Visual Studio desktop programs.

11 A New “Empty” Web Site There is a project directory

12 The Solution Files Hello.sln holds Visual Studio settings associated with this web site (project). You can look at it with NotePad. Hello.suo is a binary file Hidden by default. You may not see it. Holds Visual Studio state information. These files are used only by Visual Studio. Not part of the web app. Not deployed to a web server. Both of these files can be reproduced by Visual Studio at any time if they are deleted. Can generally be ignored.

13 The Web Site Directory C:\Users\turnerr\Documents\Visual Studio 2015\WebSites\Hello The files in this directory are the web app. Will be deployed to the web server. Will be in a virtual directory on the Internet.

14 The web.config File Double click to open in VS editor

15 The web.config File Every ASP.NET web app has an XML configuration file called web.config. ASCII text Holds information used by the server and (possibly) by application code. Can be edited with any plain text editor. Even on the server We will learn more about config files throughout the course. Can ignore for now.

16 Initial web.config

17 Adding a Web Page Note: Website menu

18 Add File Default.aspx Note file name. This is the usual starting page for an ASP.NET web site.

19 Default.aspx Click here to expand this tree node.

20 Default.aspx.cs Visual Studio has also created the “code behind” file, Default.aspx.cs Double click on the file name to open it in the VS editor.

21 Default.aspx.cs The initial file doesn’t do anything.

Default.aspx 22 Click on Design

23 The Design View A WYSIWYG editor for web pages. View > Toolbox

24 The Design Surface Click here to see Source view.

25 Source View Click here to return to Design view.

26 Design View Click inside Div box. Then double click on Label in Toolbox.

27 Add a Label Right click on Label. Select Properties. Set Text property to Hello, World!

28 Label Properties Click here to view in browser.

29 Page in Chrome

30 What We Wrote

Look at the browser’s page source 31 In Chrome, right click in the page to open context menu. Then select "View page source".

32 What the Browser Received

33 What’s happening here? When a browser requests an aspx page from an IIS (Microsoft) web server, IIS retrieves the file and passes it to ASPX for processing.

34 What’s happening here? ASPX translated what we wrote into what the browser saw. Using the visual designer, we wrote the HTML-like code shown on a previous slide. Visual Studio’s built-in web server translated that code into the real HTML code that the browser received. Note that there is a single HTML form. The browser rendered the HTML as the page that we saw.

35 Translating ASPX to HTML All tags are instructions to the server. Removed and processed by the server. Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

36 Translating ASPX to HTML All tags are ASPX controls. Replaced by HTML as the aspx file is processed by ASPX on the server. ASPX compiles an object corresponding to each control. The object emits HTML text as the page is rendered on the server. Any HTML text is passed to the browser unchanged.

37 Translating ASPX to HTML Hello, World! ASPX HTML

38 Add Some Style Back in the Designer Stop the program. Debug > Stop Debugging or Shift+F5 or Click “Stop” Button In Design view, right click on the label and select Properties. Properties window will appear. Expand Font and set Font properties Bold: True Name: Arial Size: XX-Large Set ForeColor property to Red

39 Design View

40 Give the Page a Title Select DOCUMENT Click the Play button to display the page in the browser.

41 Our Page in Chrome Title

42 What We Wrote “Properties” became attributes in the element.

43 What the Browser Received

44 The Code-Behind File View Solution Explorer Expand Default.aspx Double click on Default.aspx.cs to open the source code file in an editor window.

45 Class _Default Page_Load will be executed after Default.aspx has been retrieved from the disk and before the page is rendered on the server.

46 Dynamically Alter the Page Click the Play button to display the page in the browser.

47 The New Version in Chrome

48 What We Wrote Default.aspx has not changed.

49 What the Browser Received The text inside the is different now.

50 What’s happening here? The server read file Default.aspx The server instantiated the label control as an object. With the properties that we had set. The server read and compiled Default.aspx.cs, and then invoked our Page_Load method. Our code modified properties of the Label object. Lable1.Text Label1.ForeColor The server invoked a method of the Label object. Output yourself as HTML. The browser saw the resulting HTML. End of Section

51 Getting User Input Let’s modify the page to get the user’s name and customize the greeting for the user. Do this in the Page_Load event handler. Back in the Designer Stop the program. Debug > Stop Debugging or Shift+F5 or Click “Stop” Button View the toolbox Position the cursor above <asp:Label... Press Enter several times to add some space above the label. Position the cursor at the top of the div.

52 Getting User Input In the Toolbox, double click Label to add another Label to the page. Press Enter to move the cursor down to the next line. In the Toolbox, double click TextBox. You may need to scroll down in the Toolbox. Resize the Textbox as shown on the next slide.

53 Getting User Input

54 Modify the Page in the Designer Properties that we will modify in the code behind should have meaningful names. Give the original label a name. lblGreeting in its (ID) Property Set text for new label to “Please enter your name then click OK.” Set ID property of the TextBox to tbName.

55 In the Designer

56 Add a Button Position the cursor between the textbox and Hello, World! Double click Button in ToolBox. Set its Text property to OK. Set its ID to btnOK. Resize the button, making it a bit larger.

57 Adding a Button

58 Adding a Button Double click on the button to generate an event handler for the click event. Add code to the event handler as shown in the next slide.

59 The Button-click Event Handler Click the Play button (or press F5).

60 The Initial Page in Chrome Enter your name and then click OK.

61 After Clicking OK

What We Wrote

63 What the Browser Saw Initially

64 What the Browser Saw After the Click End of Section

Debugging in Visual Studio Click in the grey margin on the left side of a code page to set a breakpoint. When the breakpoint is hit, we can examine variables. And even change them! After stopping at a breakpoint, we can single step the program. 65

Breakpoints Set 66 Click the Play button.

Breakpoint Hit 67

The Debug Menu 68

Examining Variables Drag the cursor over lblGreeting.Text to select it. Then right click and select QuickWatch from the context menu that pops up. 69

Changing Variables at Breakpoints 70 Right click on the Value and select Edit Value.

Changing Variable at Breakpoint 71 Press F5 to continue. Enter new value for lblGreeting.Text (with quotation marks.) Press Enter then click Close.

Result 72 End of Section

73 Files Let’s see what files we have created. The WebSites Directory

74 Directory Hello These files are plain text files. Can opened and edited in NotePad These files are the web app. Can be copied to an IIS web server and accessed on the Internet

75 Projects Directory

76 Project Files These files are used by Visual Studio to manage the project. Remember settings, etc. Don’t need to look at them. Must not modify. Can be deleted. Visual Studio will recreate them the next time we open the web site (but any settings that we have changed will revert to their default values.)

77 Assignment Review the slides for this presentation. Do the examples from this lecture for yourself if you didn’t do them in class. Read (skim) Chapters 1 and 2 of Beginning ASP.NET in C# and VB