To Lecture Notes

IT 230 -- 4/8/09

Review Questions

1. What is wrong with these links on your index page?
   

   <P><A href=http://ectweb2.cs.depaul.edu/ssmith/proj1/proj1.htm
         target=new>Project 1</A></P>
   
   <LINK href=http://ectweb2.cs.depaul.edu/ssmith/styles.css>
   

   Ans: Tag names should not be upper case, attribute values should be in double quotes, the hyperlink addresses should be relative, not absolute, the link tag should be a combination start/end tag that ends with />, don't use target=new for pages within your own website.
    
2. What is the file extension for an ASP.Net file?
   Ans: .aspx.
    
3. What is the first tag in an ASP.Net Webpage file?
   Ans: The page tag

   <%@ Page Language=C# %>
   

4. Write the XHTML tag for an ASP.Net TextBox control with name txtInput and text Enter cost. Ans:

   <asp:TextBox runat=server ID=txtInput Text=Enter cost />
   

5. Write the XHTML tag for an ASP.Net Button control with name btnSubmit and text Submit Value. Also insure that the width and height of the button are 100 pixels by 50 pixels. Ans:

   <asp:Button runat=server ID=btnSubmit Text=Submit Value
            Width=100px Height=50px />
   

6. What are the delimiters for C#.Net code embedded in an HTML file?
   Ans: <%= and %>
    
7. What is a code-behind file?
   Ans: A file used in Visual Studio that only contains C# code. These files end with the extension .aspx.cs or .aspx.designer.cs.
    
8. List four important windows used when working with a Visual Studio ASP.Net project.
   Ans: (1) Toolbox, (2) Properties Window, (3) Solution Explorer, (4) Page window that can be view in Design (WYSIWYG) or Code View.
    
9. What is an event handler? How do you create one in Visual Studio?
   Ans: An event handler is a C# method that gets executed when its corresponding event fires (for example a Click event).
    
10. List the steps for converting a Visual Studio ASP.Net project with code-behind files to a file suitable for uploading to ASP.Net.
    Ans: Here are the steps.

Classes and Objects

• An object consists of data together with procedures considered as a single unit to be manipulated by the programmer. Objects can also contain events.
   
• A property is a piece of data in an object. To be useful, a property should not have the same value for all objects.
   
• A method is a procedure that an object can use to manipulate the data, or otherwise accomplish something.
   
• An event is an external stimulus to which an object can respond. Often an object reponds to an event by executing a special method called an event handler.
   
• A class is, conceptually, the collection of all objects of the same class, for example, all TextBox objects. If you like Miller analogies:
   
  
  object : class :: cookie : cookie cutter
   
  object : class :: house : blueprint
   
  
• In C#, an object is created from a class by calling a constructor with the new operator.
   
• The object is an instantiation of the class.
   
• Here is a C# statement that instantiates the object d from the class DateTime:

  d = new DateTime(1776, 7, 4);
  

Practice Problem

• Identify properties, methods and events for the following classes:
   
  
  1. BasketballPlayer
      
  2. Coin
      
  3. Button on a Web page

The C# Language

• Look at these documents:
   
  
  .Net Overview
   
  Constants, Dataclasss and Variables
   
  
• A UML Class Diagram shows the class name, class properties, and class methods.
   
  
• In the testing code for the preceding examples, the C# method call Response.Write is equivalent to the JavaScript method call Document.write. Both write output directly the HTML or ASP.Net document.
   
• A constructor is a special method that creates an object from a class. It is called using the new operator. Example:
  

  DateTime d;
  d = new DateTime(1776, 7, 4, 14, 0, 0);
  

• A static member is a member (property or method) that is called using a class name rather than an object name. For example:
  

  DateTime d;
  d = DateTime.Now;
  

Web.config Files

• Each folder on ectweb2 that contains .aspx files should contain a Web.config file with the following contents at a minimum:

  <configuration>
      <system.web>
          <customErrors mode=Off />
      </system.web>
  </configuration>
  

• Web.config files can contain other information, like database connection strings, debugging specifications, information about session state, tracing, globalization, and security.

Examples

• Look at these example Examples Page: 8, 10, 11, 12, 17.
   

Project Proj2

• Look at Project Proj2. Use Examples 12 (temperature-descriptors1.aspx) and 17 (flintstones.aspx) to help you.