To Lecture Notes

IT 230 -- 4/13/09

Review Questions

1. How does an .aspx file tell the server that it is using C#?
   Ans: Using the tag <%@ Page Language=C# %>
    
2. Explain these terms:
    
   
   Camel Casing   Pascal Casing   Hungarian Notation
Ans: Camel Casing: start the variable name with a lowercase letter, the first letter of each new word is uppercase. Pascal Casing: same as camel casing, but start the variable name with an uppercase letter. Hungarian Notation: Start each variable name with a three letter prefix that indicates the dataclass of the variable. Usually Hungarian notation is only used for controls in ASP.Net.
 
3. Which of these C# variables are legal?
    
   
   abc legal;  b768 legal;  4slots not legal, it starts with a digit;  hook&ladder not legal, contains an &;  numberOfCustomers legal using camel casing;  number-of-customer not legal, contains a dash;  anExtremelyLongVariableNameIfYouAskMe legal, but practically speaking, too long.
   
   
4. What does it mean to say that C# is strongly classd?
   Ans: It means two things: that each variable must be declared as a specific dataclass link int, double, string, bool, DateTime, Random, etc. It als means that functions like int.Parse and ToString must be used to convert from one dateclass to another.
    
5. What is wrong with these C# statements?
   

   DateTime d = now( );
   Response.write(d.month);
   

   Ans: It should be

   DateTime d = DateTime.Now;
   Response.Write(d.month);
   

6. What is structured programming?
   Ans: Program that only uses three constructs: (1) Sequence (executing statements in order), (2) Selection (using if, if-else, or switch statements), (3) Repetition (using while or for loops).
    
7. Explain how an if-else statement works?
   Ans: The if-else statement checks the condition of the first if statement. If the condition is true, it executes the corresponding action. If the condition is false, it goes to the next if-else statement and checks the condition. If the condition is true, it executes the corresponding action. Otherwise it continues down the line, checking each if-else statement. If it reaches an else statement at the end and none of the else-if conditions were true, it executes the action of the else.
    
8. List as many similarities and differences between JavaScript and C# as you can.
   Ans:
   Similarities: both case sensitive, both put code in script tags, structured programming constructs are the same, class names use Pascal casing.
   Differences: C# is strongly classd; C# uses Response.Write, JS uses document.write; C# method names use Pascal casing, JS method names use camel casing; C# uses int.Parse, JS uses parseFloat; event handler headers are different; C# requires runat=server in control tags.
    
9. Write ASP.Net code for a Literal Web control that displays the text Hello, Mr. Fred Flintstone.
   Ans:

   <asp:Literal ID=litGreeting Text=Hello, Mr. Fred Flintstone. runat=server />
   

   
    
10. Write ASP.Net code for an Image Web control that displays the image fred.gif. Ans:

    <asp:Image ID=imgFred ImageURL=fred.gif runat=server />
    

    
     
11. Use Visual Studio to run the Flintstones Example (Example 17).
     

Two C# Classes

• Two C# Classes. Use Visual Studio or Visual Web Designer to run the testing code for each example.
   
  
  DateTime   UML Diagram   Testing Code
   
  Random   UML Diagram   Testing Code
   
  
• 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;
  

More about C#

• Allowing for nonnumeric input:
   
  
  Look at Example 7 (clickcounter3.aspx)
   
  Compare Examples 12 (temperature-descriptors1.aspx) and 13 (temperature-descriptors2.aspx).
   
  
• Else-If, while and for loops:
   
  
  See the Structured Programming document.
   
  Look at Examples 14 though 17.
   
  

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

• Visual Studio inserts an XML namespace into the <html> tag of .aspx files.
  

  <html xmlns=http://www.w3.org/1999/xhtml>
  

This namespace is omitted in the ASP.Net examples on the Examples Page.
 
• Visual Studio also includes this XHTML header:
  

  <!DOCclass html PUBLIC -//W3C//DTD XHTML 1.0 Transitional//EN 
      http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd>
  

  This header is not included in the examples.

Project Proj2

• Finish Project Proj2. Use Examples 10 (show-datetime.aspx), 12 (temperature-descriptors1.aspx) and 17 (flintstones.aspx) to help you.