To Lecture Notes

IT 230 -- 4/20/09

Review Questions

1. What are the differences between HTML controls and ASP.Net Web controls?
   Ans: (1) HMTL control tags are input tags, ASP.Net Web controls start with the prefix asp: and must include the attribute runat=server, (2) HTML commands are posted to a separate .aspx page on the server when the form tag includes action and method attributes, an ASP.Net Web page are, by default, when posted to the server is posted back to itself. An ASP.Net web page is posted to the server when a button is clicked or when a control with its AutoPostBack property is set to true.
    
2. What does the AutoPostBack property do?
   Ans: See answer to question 1.
    
3. What is the difference between the RadioButton control and the RadioButtonList Web controls?
   Ans: A RadioButton control, by default, is separate from all the other RadioButton controls. They can be grouped by setting the ButtonGroup property to the same string. A RadioButtonList contains several RadioButton controls. They are automatically grouped together so that only one of them can be checked at a time.
    
   
4. How does ASP.Net know which event handler to execute when a button is clicked?
   Ans: The event handler is specified in an On attribute (for example, OnClick). Other controls have other events, such as TextChanged, CheckedChanged, SelectedIndexChanged, or SelectedDateChanged.

   
    
   

5. Create an ASP.Net application that displays all of the selected items in a CheckBoxList control in a Literal control. Use a for loop to iterate through all of the choices.

   Ans: Application   Source Code

More ASP.Net Web Controls

• CheckBox and CheckBoxList
   
  
• DropDownList
   
  
• Calendar
   
  
• HiddenField
   
  
• Look at the Midterm Review Guide: properties, methods, and events of controls.
   
  
• Look at Examples 25 through 28.

The String Class

• Abbreviated String Class UML Diagram with testing code for the methods Insert, IndexOf, Substring, and PadLeft.
   
• Although most class names are spelled with Pascal casing, the string class is an exception. It is spelled with camel casing.
   
• A shortcut for the constructor call
  

  string s = new string(abc);
  

  is

  string s = abc;
  

• The characters in a string are indexed starting with zero on the left. For example, in the string abc, 'a' has index 0, 'b' has index 1, and 'c' has index 2.
   
• Write C# code to test the string class.
   
• Practice Problems: assume an input textbox txtIn and an output textbox txtOut.
   
  
  1. Get a string from txtIn; convert the string to uppercase and put the result in txtOut.
      
  2. Get a string from txtIn; determine put its length in txtOut.
      
  3. Get a string from txtIn, put yes in txtOut if the string contains at least one vowel, otherwise put no in txtOut.
  
  

Posting Pages to the Server

• ASP.Net controls usually post their data to the same page. See Example 29.
   
• Data in HTML controls on an HTML form are posted to a separate .aspx page.
   
• The action and method attributes in the form tag of the HTML page determine where and how the data gets posted. For example
  

  <form action=destination.aspx method=get>
  

• The get method appends data to the end of a URL when posting data. Here is an example URL with appended data

  http://ectweb2.cs.depaul.edu/ssmith/
  destination.aspx?txtName=Stan&txtAge=45
  

• Example 30 uses method=get to post data to the verify1.aspx page. Here is the form tag for posting data with method=post:
  

  <form action=destination.aspx method=post>
  

• The post method submits data in the HTTP header, so there is no appended data to the URL:
  

  http://ectweb2.cs.depaul.edu/ssmith/destination.aspx
  

  
  
• Example 31 uses method=post to post data to the verify1.aspx page.

ASP.Net Validation Controls

• ASP.Net offers validation controls to validate (check the correctness) of a field in a control before it is posted back to the server.
   
• ASP.Net generates JavaScript code to perform this validation.
   
• Here are four validation controls and their use:
   
  

  RequiredFieldValidator	Checks that the field is not blank.
  CompareValidator	Checks that a field is greater than or less then a given value.
  RangeValidator	Checks that a field is within a given range.
  RegularExpressionValidator	Checks a field using a regular expression.

  
  
• A table of Common Regular Expression Symbols
   
• Some Common Regular Expressions shown by the Visual Studio Regular Expression Editor.
   
• Practice Problems on Regular Expressions: write a regular expression that validates each of the following
   
1. Five digit zip code. Example: 64538
    
2. Five digit zip code with optional 4 digit extension. Example: 64538-7346
    
3. One of the letters F, f, M, or m, for male or female. Example: F
    
4. Social security number. Example: 436-43-4399
    
5. Legal C# variable name. Example: entry5
    
6. Telephone number. Example: (312)728-5487
    
7. Illinois drivers license number.


• Use Example 34 to check your answers to the practice problems.
   
• Example 32 uses validation controls to validate the data that is posted back to the same page.
   
• Example 33 uses validation controls, but posts the data to a different page (verify2.aspx).

Projects 3 and 4

• Look at Project 4.
   
• Finish Project 3.