Create a Windows Forms application. Use the following names for the project and solution, respectively: Customer Project and Customer Solution. Save the application in the VB9e\Chap09 folder.

Create the interface shown in Figure 9-35. The File menu should have an Exit option. Change the lblMessage control’s Visible property to False.

Code the File menu’s Exit option.

The lblMessage control should disappear when a change is made to any of the text boxes. Create one event-handling Sub procedure to handle this task.

Code each text box’s Enter event procedure.

The Save button should save the customer information to a sequential access file named customers.txt. Before saving the information, be sure to verify that all of the text boxes contain data; display an appropriate message if at least one text box is empty. Use the following format when saving the information: Save the customer’s first name and last name, separated by a space character, on the same line. Then, on the next line, save the customer’s address, followed by a comma, a space character, the city name, a comma, a space character, and the ZIP code. A blank line should separate each customer’s information from the next customer’s information. Figure 9-36 shows a sample of the sequential access file.

Save the solution and then start and test the application. Stop the application and verify the contents of the customers.txt file.