Lab 12 - Files

Structure Chart
Printable Structure Chart
Video clip about Lab 12 (6:10 min)

Grader

For this project you may create your own interface or use the one provided in the Shell folder on the Content tab in Angel. If you use the shell "make it your own" by changing colors, fonts, and/or rearrange the layout.

This program will maintain a list file containing information about friends. It will also display the contents of the file when the user requests it.

Form Load Event

Use an Inputbox to query the user for file name and location of the Friends file.
Open the file (output stream)

Note: If the program can not open the file because of user input error it will die. This is normally unacceptable but since we have not covered error handling we will not address this problem at this time. Just be sure to enter valid path and filename, including a .txt extension.

Hints:

To create the shell for the Load event for the form double click on any blank space of the form

OR

choose (Form Events) from the Object List Box

and then the Load Event from the Event List Box

Image of Event List box

You can take advantage of the DefaultResponse argument of the InputBox function to populate the Textbox portion of the InputBox( ) with the file name so that you do not have to type it every time you run your program.

………InputBox( “prompt”,”title”, “E:\Friends.txt”)

Since you will be either creating a new file or adding to an existing file set the Append argument to True when you open the file.
The variable that you use to store the file’s path and name must be declared at Class Level (in the declaration section) so the file name and path entered in the InputBox( ) is available no matter which procedure is opening the file.
Since you will be referencing the StreamWriter object in more than one procedure (Form's Load when opening the file, Button's Click event when writing to the file, and the Form's Closed event when closing the file) the StreamWriter object should be declared at Class level.

Add Friend

Will write the information provided via textboxes to the Friend text file.

The first and last name are required fields
In addition to the five values provided by the user add a number as the first field in the record to act as key field. For now do not worry about the key field being unique. Create a Class level variable to hold the key field value and increment it each time you write a new record to the file. The number will start over each time you execute the program. We will add code to make the value unique later.
Each time new data is written to the file clear all the textboxes and return focus to the first name textbox.

An example of the resulting file. Note: Blank lines indicate field values not provided by the user.

image of Friend Text File

Hints:

Use a separate WriteLine statement for each data value.
Check the file frequently to verify the information is being written to the file.
IMPORTANT: You must Close the file before checking it. Since the StreamWriter object "buffers" output some data will not actually be written to the file until you Close it. This means that if you check the file when the program is still running data may be missing.

Display All

Will read the Friend file and display the information for all the friends on the form, one friend per line.

Display the key field value only if the user checks the appropriate checkbox.
Align each field value in columns
Provide column headings

Hints:

Since a file may not be open for reading at the same time it is open for writing you will need to Close the file before you can open it for reading.
Use the StreamReader's Peek method to recgonize when you have reached the end of the Friends file.
Use the PadRight string method to create columns.
Use ControlChars.NewLine to report each friend on a separate line.
After displaying all the friends you will need to Close the file and reopen it for writing so that you can continue to add new friends to the file.

Form FormClosed Event

Close all open files (Streams)

Hints:

To create the shell for the FormClosed event for the form choose (Form Events) from the Object List Box and then the FormClosed Event from the Event List Box

Lab 12 - Files

Structure Chart Printable Structure Chart Video clip about Lab 12 (6:10 min)

Grader

For this project you may create your own interface or use the one provided in the Shell folder on the Content tab in Angel. If you use the shell "make it your own" by changing colors, fonts, and/or rearrange the layout.

Form Load Event

Use an Inputbox to query the user for file name and location of the Friends file.

Open the file (output stream)

Note: If the program can not open the file because of user input error it will die. This is normally unacceptable but since we have not covered error handling we will not address this problem at this time. Just be sure to enter valid path and filename, including a .txt extension.

Hints:

To create the shell for the Load event for the form double click on any blank space of the form

OR

choose (Form Events) from the Object List Box

and then the Load Event from the Event List Box

You can take advantage of the DefaultResponse argument of the InputBox function to populate the Textbox portion of the InputBox( ) with the file name so that you do not have to type it every time you run your program.

………InputBox( “prompt”,”title”, “E:\Friends.txt”)

Since you will be either creating a new file or adding to an existing file set the Append argument to True when you open the file.

The variable that you use to store the file’s path and name must be declared at Class Level (in the declaration section) so the file name and path entered in the InputBox( ) is available no matter which procedure is opening the file.

Since you will be referencing the StreamWriter object in more than one procedure (Form's Load when opening the file, Button's Click event when writing to the file, and the Form's Closed event when closing the file) the StreamWriter object should be declared at Class level.

Add Friend

Will write the information provided via textboxes to the Friend text file.

The first and last name are required fields

Each time new data is written to the file clear all the textboxes and return focus to the first name textbox.

An example of the resulting file. Note: Blank lines indicate field values not provided by the user.

Hints:

Use a separate WriteLine statement for each data value.

Check the file frequently to verify the information is being written to the file.

IMPORTANT: You must Close the file before checking it. Since the StreamWriter object "buffers" output some data will not actually be written to the file until you Close it. This means that if you check the file when the program is still running data may be missing.

Display All

Will read the Friend file and display the information for all the friends on the form, one friend per line.

Display the key field value only if the user checks the appropriate checkbox.

Align each field value in columns

Provide column headings

Hints:

Since a file may not be open for reading at the same time it is open for writing you will need to Close the file before you can open it for reading.

Use the StreamReader's Peek method to recgonize when you have reached the end of the Friends file.

Use the PadRight string method to create columns.

Use ControlChars.NewLine to report each friend on a separate line.

After displaying all the friends you will need to Close the file and reopen it for writing so that you can continue to add new friends to the file.

Form FormClosed Event

Close all open files (Streams)

Hints:

To create the shell for the FormClosed event for the form choose (Form Events) from the Object List Box and then the FormClosed Event from the Event List Box

Structure Chart
Printable Structure Chart
Video clip about Lab 12 (6:10 min)