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Getting Started with ASP.NET

Beginning ASP.NET 4.5.1 in C# and VB

Chapters 1 and 2

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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 20073

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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.

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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.

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Creating a New Web App In Visual Studio, File > New Web Site (NOT New project)

Web Site vs. Project in Visual Studio.https://msdn.microsoft.com/en-us/library/dd547590(v=vs.110).aspx

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Empty Web Site

Web Site NameCheck this setting

Check this setting

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View Solution Explorer

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The Solution Explorer

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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.

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A New “Empty” Web Site

There is a project directory

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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.

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The Web Site DirectoryC:\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.

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The web.config File

Double click to open in VS editor

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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.

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Initial web.config

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Adding a Web Page

Note: Website menu

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Add File Default.aspx

Note file name.

This is the usual starting page for an ASP.NET web site.

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Default.aspx

Click here to expand this tree node.

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Default.aspx.csVisual Studio has also created the “code behind” file, Default.aspx.cs

Double click on the file name to open it in the VS editor.

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Default.aspx.cs

The initial file doesn’t do anything.

Default.aspx

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Click on Design

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The Design ViewA WYSIWYG editor for web pages.

View > Toolbox

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The Design Surface

Click here to see Source view.

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Source View

Click here to return to Design view.

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Design View

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

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Add a Label

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

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Label Properties

Click here to view in browser.

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Page in Chrome

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What We Wrote

Look at the browser’s page source

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In Chrome, right click in the page to open context menu.Then select "View page source".

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What the Browser Received

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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.

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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.

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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" %>

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Translating ASPX to HTML

All <asp:xxx > 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.

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Translating ASPX to HTML

<span id="Label1">Hello, World!</span>

ASPX

HTML

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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

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Design View

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Give the Page a Title

Select DOCUMENT

Click the Play button to display the page in the browser.

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Our Page in ChromeTitle

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What We Wrote

“Properties” became attributes in the <asp:Label> element.

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What the Browser Received

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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.

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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.

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Dynamically Alter the Page

Click the Play button to display the page in the browser.

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The New Version in Chrome

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What We Wrote

Default.aspx has not changed.

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What the Browser Received

The text inside the <span> is different now.

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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

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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.

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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.

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Getting User Input

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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.

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In the Designer

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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.

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Adding a Button

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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.

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The Button-click Event Handler

Click the Play button (or press F5).

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The Initial Page in Chrome

Enter your name and then click OK.

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After Clicking OK

What We Wrote

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What the Browser Saw Initially

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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.

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Breakpoints Set

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Breakpoint Hit

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The Debug Menu

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Examining Variables

Drag the cursor over lblGreeting.Text to select it. Then right click and select QuickWatch from the

context menu that pops up.

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Changing Variables at Breakpoints

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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

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Files Let’s see what files we have created.

The WebSites Directory

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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

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Projects Directory

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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.)

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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 4.5.1 in C# and VB