Introduction

The similarities of both types are:

• A directory or a file can be created. One of the restrictions is that two files cannot have the same name inside of the same directory. Two directories cannot have the same name inside of the same parent directory.
• A directory or a file can be renamed. If a directory is renamed, the "path" of its file(s) changes
• A directory or a file can be deleted. If a directory is deleted, its files are deleted also
• A directory or a file can be moved. If a directory moves, it "carries" all of its files to the new location
• A directory or a file can be copied. A file can be copied from one directory to another. If a directory is copied to a new location, all of its files are also copied to the new location

1. Create a new Windows Application, named WattsALoan2
2. In the Solution Explorer, right-click Form1.vb and click Rename
3. Type WattsALoan.vb and press Enter
4. Design the form as follows:
    

   Control Name Text Label   If this is a new loan, enter a new account number and the name of the customer who is requesting the loan Label   To open a previously prepared loan, enter its account number and press Tab Label   Acnt #: Label   Customer Name: Label   Customer: TextBox txtAccountNumber   TextBox txtCustomerName   Label   Empl #: Label   Employee Name: Label   Prepared By: TextBox txtEmployeeNumber   TextBox txtEmployeeName   Button btnNewEmployee   Button btnNewCustomer   Label   Loan Amount: TextBox txtLoanAmount   Label   Interest Rate: TextBox txtInterestRate   Label   % Label   Periods TextBox   txtPeriods Button btnCalculate Calculate Label   Monthly Payment: TextBox txtMonthlyPayment   Button btnClose Close

5. Double-click the Calculate button and implement its event as follows:
    

   Imports System.IO Public Class WattsALoan Private Sub btnCalculate_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btnCalculate.Click Dim LoanAmount As Double Dim InterestRate As Double Dim Periods As Double Dim MonthlyPayment As Double Try LoanAmount = CDbl(txtLoanAmount.Text) Catch ex As Exception MsgBox("Invalid Loan Amount") End Try Try InterestRate = CDbl(txtInterestRate.Text) Catch ex As Exception MsgBox("Invalid Interest Rate") End Try Try Periods = CDbl(txtPeriods.Text) Catch ex As Exception MsgBox("Invalid Periods Value") End Try MonthlyPayment = Pmt(InterestRate / 12 / 100, _ Periods, -LoanAmount, 0, _ DueDate.BegOfPeriod) txtMonthlyPayment.Text = FormatCurrency(MonthlyPayment) End Sub End Class

6. In the Class Name combo box, select btnClose
7. In the Method Name combo box, select Click and implement the event as follows:
    

   Private Sub btnClose_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles btnClose.Click End End Sub

8. To create a new form, on the main menu, click Project -> Add Windows Form...
9. In the Templates list, make sure Windows Form is selected.
   Set the Name to NewEmployee and click Add
10. Design the form as follows:
     

    Control Text Name Label Employee #: TextBox txtEmployeeNumber Label Employee Name: TextBox txtEmployeeName Button Create btnCreate Button Close btnClose

11. Double-click the Close button
12. Implement the event as follows:
     

    Imports System.IO Public Class NewEmployee Private Sub btnClose_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btnClose.Click Close() End Sub End Class

13. In the Solution Explorer, right-click WattsALoan.vb and click View Code
14. In the Class Name combo box, select btnNewEmployee
15. In the Method Name combo box, select Click and implement the event as follows:
     

    Private Sub btnNewEmployee_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles btnNewEmployee.Click Dim FormEmployee As NewEmployee = New NewEmployee() FormEmployee.ShowDialog() End Sub

16. Save the file

Before using a directory, you must first have it. You can use an existing directory if the operating system or someone else had already created one. You can also create a new directory. Directories are created and managed by various classes but the fundamental class is called Directory. Directory is a static class. All of its methods are static, which means you will never need to declare an instance of the Directory class in order to use it.

Besides the Directory class, additional operations of folders and sub-folders can be performed using the DirectoryInfo class.

To create a directory, you can call the CreateDirectory() method of the Directory class. This method is available in two versions. One of the versions uses the following syntax:

Public Shared Function CreateDirectory(path As String) As DirectoryInfo

This method takes as argument the (complete) path of the desired directory. Here is an example:

E:\Programs\Business Orders\Customer Information

When this method is called:

1. It first checks the parent drive, in this case E.
   If the drive doesn't exist, because this method cannot create a drive, the compiler would throw a DirectoryNotFoundException exception
2. If the drive (in this case E) exists, the compiler moves to the first directory part of the path; in this case this would be the Programs folder in the E drive.
   If the folder doesn't exist, the compiler would create it. If that first director doesn't exist, this means that the other directory(ies), if any, under the first don't exist. So, the compiler would create it/them
3. If the first directory exists and if there is no other directory under that directory, the compiler would stop and would not do anything further.
4. If the directory exists and there is a sub-directory specified under it, the compiler would check the existence of that directory.
   If the sub-directory exists, the compiler would not do anything further and would stop.
   If the sub-directory doesn't exist, the compiler would create it
5. The compiler would repeat step 4 until the end of the specified path

The Directory.CreateDirectory() method returns a DirectoryInfo object that you can use as you see fit.

1. In the Class Name combo box, select (WattsALoan Events)
2. In the Method Name combo box, select Load and implement the event as follows:
    

   Private Sub WattsALoan_Load(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles Me.Load Dim Folder As String Dim EmployeeWriter As StreamWriter Dim Filename As String = "Employees.wal" Dim EmployeeInformation As FileInfo = _ My.Computer.FileSystem.GetFileInfo(Filename) Folder = "C:\Watts A Loan" If Not Directory.Exists(Folder) Then Directory.CreateDirectory(Folder) Dim strFilename As String = Folder & "\Employees.wal" Dim fiEmployees As FileInfo = New FileInfo(strFilename) ' If the employees file was not created already, ' then create it If Not EmployeeInformation.Exists Then EmployeeWriter = EmployeeInformation.CreateText() ' And create a John Doe employee Try EmployeeWriter.WriteLine("00-000") EmployeeWriter.WriteLine("John Doe") Finally EmployeeWriter.Close() End Try End If End If End Sub

3. In the Solution Explorer, right-click NewEmployee and click View Code
4. In the Class Name combo box, select btnCreate
5. In the Method Name combo box, select Click and implement the event as follows:
    

   Private Sub btnCreate_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles btnCreate.Click Dim Filename As String = "C:\Watts A Loan\Employees.wal" Dim EmployeeInformation As FileInfo Dim EmployeeWriter As StreamWriter EmployeeInformation = My.Computer.FileSystem.GetFileInfo(Filename) ' Normally, we should have the file already but just in case... If Not EmployeeInformation.Exists Then EmployeeWriter = EmployeeInformation.CreateText() Else ' If the file exists already, then we will only add to it EmployeeWriter = EmployeeInformation.AppendText() End If Try EmployeeWriter.WriteLine(txtEmployeeNumber.Text) EmployeeWriter.WriteLine(txtEmployeeName.Text) Finally EmployeeWriter.Close() End Try txtEmployeeNumber.Text = "" txtEmployeeName.Text = "" txtEmployeeNumber.Focus() End Sub

6. Click the WattsALoan.vb [Design] tab

Before using or creating a directory, you can first check if it exists. This is because, if a directory already exists in the location where you want to create it, you would be prevented from creating one with the same name. In the same way, if you just decide to directly use a directory that doesn't exist, the operation you want to perform may fail because the directory would not be found.

To check whether a directory exists or not, you can call the Directory.Exists() Boolean static method. Its syntax is:

Public Shared Function Exists(path As String) As Boolean

This method receives the (complete) path of the directory. If the path exists, the method returns true. If the directory doesn't exist, the method returns false.

One of the most routine operations performed in a directory consists of looking for a file. Microsoft Windows operating systems and the user's intuition have different ways of addressing this issue. The .NET Framework also provides its own means of performing this operation, through various techniques. You can start by checking the sub-directories and files inside of a main directory.

To look for files in a directory, the DirectoryInfo class can assist you with its GetFiles() method, which is overloaded with three versions.

1. In the Class Name combo box, select txtAccountNumber
2. In the Method Name combo box, select Leave and implement the event as follows:
    

   Private Sub txtAccountNumber_Leave(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles txtAccountNumber.Leave Dim Filename As String Dim LoanPath As String Dim FileFullname As String Dim ListOfLoans() As FileInfo Dim LoanReader As StreamReader Dim LoanFolder As DirectoryInfo Dim LoanInformation As FileInfo Dim Found As Boolean Found = False LoanPath = "C:\Watts A Loan" LoanFolder = New DirectoryInfo(LoanPath) ListOfLoans = LoanFolder.GetFiles("*", _ SearchOption.AllDirectories) Filename = txtAccountNumber.Text & ".wal" FileFullname = LoanPath & "none.wal" For Each fle As FileInfo In ListOfLoans If fle.Name = Filename Then Found = True FileFullname = fle.FullName End If Next If Found = True Then LoanInformation = My.Computer.FileSystem.GetFileInfo(Filename) LoanReader = LoanInformation.OpenText Try txtAccountNumber.Text = LoanReader.ReadLine txtCustomerName.Text = LoanReader.ReadLine txtEmployeeNumber.Text = LoanReader.ReadLine txtEmployeeName.Text = LoanReader.ReadLine txtLoanAmount.Text = LoanReader.ReadLine txtInterestRate.Text = LoanReader.ReadLine txtPeriods.Text = LoanReader.ReadLine txtMonthlyPayment.Text = LoanReader.ReadLine Finally LoanReader.Close() End Try End If End Sub

3. In the Class Name combo box, select txtEmployeeNumber
4. In the Method Name combo box, select click Leave and implement the event as follows:
    

   Private Sub txtAccountNumber_Leave(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles txtAccountNumber.Leave Dim Filename As String Dim LoanPath As String Dim FileFullname As String Dim ListOfLoans() As FileInfo Dim LoanReader As StreamReader Dim LoanFolder As DirectoryInfo Dim LoanInformation As FileInfo Dim Found As Boolean Found = False LoanPath = "C:\Watts A Loan" LoanFolder = New DirectoryInfo(LoanPath) ListOfLoans = LoanFolder.GetFiles("*", _ SearchOption.AllDirectories) Filename = txtAccountNumber.Text & ".wal" FileFullname = LoanPath & "none.wal" For Each fle As FileInfo In ListOfLoans If fle.Name = Filename Then Found = True FileFullname = fle.FullName End If Next If Found = True Then LoanInformation = My.Computer.FileSystem.GetFileInfo(FileFullname) MsgBox(LoanInformation.FullName) LoanReader = LoanInformation.OpenText Try txtAccountNumber.Text = LoanReader.ReadLine txtCustomerName.Text = LoanReader.ReadLine txtEmployeeNumber.Text = LoanReader.ReadLine txtEmployeeName.Text = LoanReader.ReadLine txtLoanAmount.Text = LoanReader.ReadLine txtInterestRate.Text = LoanReader.ReadLine txtPeriods.Text = LoanReader.ReadLine txtMonthlyPayment.Text = LoanReader.ReadLine Finally LoanReader.Close() End Try End If End Sub

5. In the Class Name combo box, select btn Save
6. In the Method Name combo box, select Click and implement the event as follows:
    

   Private Sub btnSave_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles btnSave.Click Dim LoanPath As String Dim LoanWriter As StreamWriter LoanPath = "C:\Watts A Loan\" & txtAccountNumber.Text & ".wal" LoanWriter = My.Computer.FileSystem.OpenTextFileWriter(LoanPath, False) Try LoanWriter.WriteLine(txtAccountNumber.Text) LoanWriter.WriteLine(txtCustomerName.Text) LoanWriter.WriteLine(txtEmployeeNumber.Text) LoanWriter.WriteLine(txtEmployeeName.Text) LoanWriter.WriteLine(txtLoanAmount.Text) LoanWriter.WriteLine(txtInterestRate.Text) LoanWriter.WriteLine(txtPeriods.Text) LoanWriter.WriteLine(txtMonthlyPayment.Text) txtAccountNumber.Text = "" txtCustomerName.Text = "" txtEmployeeNumber.Text = "" txtEmployeeName.Text = "" txtLoanAmount.Text = "" txtInterestRate.Text = "" txtPeriods.Text = "" txtMonthlyPayment.Text = "" txtAccountNumber.Focus() Finally LoanWriter.Close() End Try End Sub

7. Execute the application to test it
8. First create a few employees as follows:
    

   Employee #	Employee Name
   42-806	Patricia Katts
   75-148	Helene Mukoko
   36-222	Frank Leandro
   42-808	Gertrude Monay

9. Process a few loans
    
10. Close the application