1. Tutorial 9 Sequential Access Files and Printing

2. Sequential Access Files Lesson A Objectives
After completing this lesson, you will be able to:
Declare StreamReader and StreamWriter object variables
Open a sequential access file
Determine whether a sequential file exists
Write information to a sequential access file
Align the text written to a sequential access file
Read information from a sequential access file
Determine whether the computer has finished reading a sequential access file
Close a sequential access file
Tutorial 9: Sequential Access Files and Printing

3. File Types
Files to which information is written are called output files, because the files store the output produced by an application
Files that are read by the computer are called input files, because an application uses the information in these files as input
Here is a list of different file types:
Sequential access files
Random access files
Binary access files
Tutorial 9: Sequential Access Files and Printing

4. Using Sequential Access Files
A sequential access file is often referred to as a text file, because it is composed of lines of text
Sequential access files are similar to cassette tapes in that each line in the file, like each song on a cassette tape, is both stored and retrieved in consecutive order (sequentially)
Tutorial 9: Sequential Access Files and Printing

5. Procedure for Using a Sequential Access File
Declare either a StreamWriter or StreamReader object variable
Create a StreamWriter or StreamReader object by opening a file; assign the object’s address to the object variable declared in Step 1
Use the StreamWriter object to write one or more lines of text to the file, or use the StreamReader object to read one or more lines of text from the file
Use the StreamWriter or StreamReader object to close the file
Tutorial 9: Sequential Access Files and Printing

6. Using StreamWriter and StreamReader Objects
In Visual Basic .NET
Use a StreamWriter object to write a sequence of characters—referred to as a stream of characters or, more simply, a stream—to a sequential access file
Use a StreamReader object to read a stream (sequence of characters) from a sequential access file
Before you create the appropriate object, you first must declare an object variable to store the address of the object in the computer’s internal memory
Tutorial 9: Sequential Access Files and Printing

7. Opening a Sequential File
Refer to Figure 9-7 in the textbook, which illustrates all of the methods used to open a sequential access file
CreateText method – Creates a file for writing a text stream
objStreamWriter = System.IO.File.CreateText(“memo.txt”)
AppendText method – Opens a file appending text to the end of the file
objStreamWriter = System.IO.File.AppendText(“sales.txt”)
OpenText method – Opens a file to read a stream of text
objStreamReader = System.IO.File.OpenText(“a:\reports\pay.txt”)
Tutorial 9: Sequential Access Files and Printing

8. Does the file exist? Avoid errors by using the Exists method
If System.IO.File.Exists(“pay.txt”) Then
Returns True or False
The Exists method returns the Boolean value True if filename exists; otherwise, it returns the Boolean value False
Tutorial 9: Sequential Access Files and Printing

9. Writing to a Sequential File
Write method
Leaves the file pointer after last character
objStreamWriter.Write(“Good”)
objStreamWriter.Write(“ Morning”) ‘ Writes on the same line
Good Morning
WriteLine method
Appends the line terminator to the end of line and leaves the file pointer ready for next line
objStreamWriter.WriteLine(“Good”)
objStreamWriter.WriteLine(“ Morning”) ’ Each is on a separate line
Good
Morning
Tutorial 9: Sequential Access Files and Printing

10. Formatting String Data
The Space function inserts spaces
objStreamWriter.Write(Space(10) & “A” & Space(5) & “B”
PadLeft – Pads a string on the left with specified character
Dim sngNetPay As Single = , strNet As String
strNet = FormatCurrency (sngNetPay)
strNet = strNet.PadLeft(15, “*”)
Results in “********$767.89”
PadRight – Pads a string on the right with specified character
Dim strName As String = “Sue”
strName = strName.PadRight(10)
Results in “Sue ” (the string “Sue” and seven spaces)
Tutorial 9: Sequential Access Files and Printing

11. Aligning Data in a Sequential File
For intRegion = 1 To 3
strSales = InputBox(“Sales amount”, “Sales”)
strSales = Format(strSales, “standard”)
objStreamWriter.WriteLine(strSales.PadLeft(8))
Next intRegion
Result (assuming the following sales amounts: , 1200, 40.80
645.75
1,200.00
40.80
Tutorial 9: Sequential Access Files and Printing

12. Reading from a Sequential File
ReadLine Method – Read a line of text from the file
strLine = objStreamReader.ReadLine()
Peek method – Looks to see if there is another character to read
Do Until objStreamReader.Peek = -1
Close method – Close the file when you are finished
objStreamReader.Close()
objStreamWriter.Close()
Tutorial 9: Sequential Access Files and Printing

13. Using a DateTimePicker Control Lesson B Objectives
After completing this lesson, you will be able to:
Add a DateTimePicker control to a form
Control the appearance of a DateTimePicker control
Format the text that appears in a DateTimePicker control
Set and retrieve the information stored in a DateTimePicker control
Retrieve the system date and time
Display a form immediately
Tutorial 9: Sequential Access Files and Printing

14. Adding a DateTimePicker Control to a Form
The DateTimePicker control allows the user to select either a date or time, and then displays the selected information in a specified format
Tutorial 9: Sequential Access Files and Printing

15. The ShowUpDown Property
The DateTimePicker control’s ShowUpDown property determines whether a list arrow button or up and down arrow button appear on the control
If the property is set to its default value, False, the control contains a list arrow button
If, on the other hand, the ShowUpDown property is set to True, up and down arrow buttons appear on the control
Tutorial 9: Sequential Access Files and Printing

16. The Format Property
You can use the Format property to control the format (style) of the date or time displayed in the DateTimePicker control
Tutorial 9: Sequential Access Files and Printing

17. Tutorial 9: Sequential Access Files and Printing

18. The Value Property
When you add a DateTimePicker control to a form, Visual Basic .NET retrieves the current date and time from your computer system’s clock, and assigns both values to the DateTimePicker control’s Value property
You can verify that fact by viewing the Value property in the Properties list
The DateTime object is simply an object that represents a date and an optional time
Tutorial 9: Sequential Access Files and Printing

19. The Value Property Example Results Me.PayDateTimePicker.Value
Me.PayDateTimePicker.Value.ToLongDateString
Friday, November 12, 2004
Me.PayDateTimePicker.Value.ToShortDateString
11/12/2004
Me.PayDateTimePicker.Value.ToLongTimeString
9:08:00 AM
Me.PayDateTimePicker.Value.ToShortTimeString
9:08 AM
Tutorial 9: Sequential Access Files and Printing

20. Using the DateTime Object
objectname.Value = New DateTime(year, month, day[, hour, minute, second])
Me.PayDateTimePicker.Value = New DateTime(2004, 2, 3)
Me.PayDateTimePicker.Value = New DateTime(2004, 9, 7, 5, 30, 18)
Me.PayDateTimePicker.Value = New DateTime(2004, 1, 6, 17, 30, 18)
Tutorial 9: Sequential Access Files and Printing

21. Retrieving the Information Stored in the Value Property
Example using “11/12/2004 9:07 AM”
Results
Me.PayDateTimePicker.Value.Month 11
Me.PayDateTimePicker.Value.Day 12
Me.PayDateTimePicker.Value.Year
2004
Me.PayDateTimePicker.Value.DayOfWeek 5
Me.PayDateTimePicker.Value.DayOfWeek.ToString
Friday
Me.PayDateTimePicker.Value.Hour 9
Me.PayDateTimePicker.Value.Minute 7
Me.PayDateTimePicker.Value.Second
Tutorial 9: Sequential Access Files and Printing

22. Text Property
The text that appears in a DateTimePicker control is stored in the control’s Text property
Visual Basic .NET automatically assigns to the Text property the contents of the Value property formatted using the setting specified in the Format property; this is illustrated in Figure 9-31 of the textbook
Tutorial 9: Sequential Access Files and Printing

23. Tutorial 9: Sequential Access Files and Printing

24. Retrieving the System Date and Time
The system date is the current date according to your computer system’s clock
The system time is the current time according to your computer system
You can retrieve the system time using the syntax TimeOfDay[.methodname], where methodname (which is optional) is ToLongTimeString, ToShortTimeString, or ToString(formatting characters)
Tutorial 9: Sequential Access Files and Printing

25. Coding the CarriageForm Load Event Procedure
The pseudocode for the CarriageForm Load event procedure is shown in Figure 9-34
The syntax of the form’s Show method is simply Me.Show()
Tutorial 9: Sequential Access Files and Printing

26. Tutorial 9: Sequential Access Files and Printing

27. Coding the AddButton Click Event Procedure
The pseudocode for the AddButton Click event is shown in Figure 9-40 of the textbook
Tutorial 9: Sequential Access Files and Printing

28. Tutorial 9: Sequential Access Files and Printing

29. Completing the Carriage House Application Lesson C Objective
After completing this lesson, you will be able to:
Add a PrintDocument control to a form
Print text using the Print and e.Graphics.DrawString methods
Code a PrintDocument control’s PrintPage event procedure
Tutorial 9: Sequential Access Files and Printing

30. Adding a PrintDocument Control to the Form
Before you can print a document within a Windows application, you need to add a PrintDocument control to the form
Tutorial 9: Sequential Access Files and Printing

31. Coding the Print Report Button’s Click Event Procedure
The Print method causes the PrintDocument control’s PrintPage event to occur
You use the PrintPage event to indicate the information you want to print, as well as how you want the information to appear in the printout
Tutorial 9: Sequential Access Files and Printing

32. Tutorial 9: Sequential Access Files and Printing

33. Coding the PrintPage Event Procedure
In this case, the PrintPage event procedure should print the contents of the events.txt file in a report format
The report should contain a report header, which describes the contents of the report, and three columns of information
The first column should list the event names, the second column the event dates, and the third column the event prices
Tutorial 9: Sequential Access Files and Printing

34. The e.Graphics.DrawString Method
You use the e.Graphics.DrawString method to print text on the printer
Some print fonts are proportionally spaced, while others are fixed-spaced, often referred to as mono-spaced
Fixed-spaced fonts use the same amount of space to print each character
Proportionally spaced fonts use varying amounts of space to print characters
Tutorial 9: Sequential Access Files and Printing