Example Application - Watts A Loan: Loan Preparation

	Watts A Loan: Loan Preparation

Introduction

Imagine you are asked to create an application for a company that is in the business of lending money, including personal loans (cash loan), car loans, furniture loans, music instrument loans, etc. One of the actions you would take consists of creating a form that an employee can use to prepare a loan presented to a customer. This is the type of example application we will create.

To implement our application, we will use the Visual Basic library to calculate the monthly payment that will be applied to the loan. This will be a file-based application. For this reason, we will create a file to store the information related to a loan.

Practical Learning: Introducing

Start Microsoft Visual Basic 2005 Professional or Microsoft Visual Basic 2005 Express Edition
To create a new application, on the main menu, click File -> New -> Project...
In the Templates list, click Windows Application
Set the name to WattsALoan2 and click OK
In the Solution Explorer, right-click Form1.vb and click Rename
Type LoanPreparation.vb and press Enter

To create a new form, on the main menu, click Project -> Add Windows Form...

In the Templates list, make sure Windows Form is selected.
Set the Name to NewEmployee and click Add

Design the form as follows:

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

Right-click the form and click View Code

In the Class Name combo box, select btnClose

In the Method Name combo box, select Click

Change the file as follows:

Imports System.IO

Public Class NewEmployee

    Private Sub btnCloseClick(ByVal sender As Object, 
                ByVal e As System.EventArgs) Handles btnClose.Click
        Close()
    End Sub
End Class

In the Class Name combo box, select btnCreate

In the Method Name combo box, select Click

Implement the event as follows:

Private Sub btnCreateClick(ByVal sender As Object, 
                ByVal e As System.EventArgs) Handles btnCreate.Click
        Dim strFilename As String = "C:\Watts A Loan\Employees.wal"
        Dim fiEmployees As FileInfo = New FileInfo(strFilename)
        Dim stwEmployees As StreamWriter = Nothing

        ' Normally, we should have the file already but just in case...
        If Not fiEmployees.Exists Then
            stwEmployees = fiEmployees.CreateText()
        Else ' If the file exists already, then we will only add to it
            stwEmployees = fiEmployees.AppendText()
        End If

        Try
            stwEmployees.WriteLine(txtEmployeeNumber.Text)
            stwEmployees.WriteLine(txtEmployeeName.Text)
        Finally

            stwEmployees.Close()
        End Try

        txtEmployeeNumber.Text = ""
        txtEmployeeName.Text = ""
        txtEmployeeNumber.Focus()
End Sub

Display the LoanPreparation form
In the Common Controls section of the Toolbox, click ToolTip and click the form

Design the form as follows:

Control	Name	Text	ToolTip on toolTip1
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		Account number of the customer requesting the loan
TextBox	txtCustomerName		Name of the customer requesting the loan
Label		Empl #:
Label		Employee Name:
Label		Prepared By:
TextBox	txtEmployeeNumber		Employee number of the clerk preparing the loan
TextBox	txtEmployeeName		Name of the clerk preparing the loan
Button	btnNewEmployee		Used to add a new employee to the company
Button	btnNewCustomer		Used to create an account for a new customer
Label		Loan Amount:
TextBox	txtLoanAmount		Amount of loan the customer is requesting
Label		Interest Rate:
TextBox	txtInterestRate		Annual percentage rate of the loan
Label		%
Label		Periods
TextBox		txtPeriods	The number of months the loan is supposed to last
Button	btnCalculate	Calculate	Used to calculate the monthly payment
Label		Monthly Payment:
TextBox	txtMonthlyPayment		The minimum amount the customer should pay every month
Button	btnClose	Close	Used to close the form

Right-click the form and click View Code

In the Class Name combo box, select btnNewEmployee

In the Method Name combo box, select Click

Change the file as follows:

Imports System.IO

Public Class LoanPreparation

    Private Sub btnNewEmployeeClick(ByVal sender As Object, 
            ByVal e As System.EventArgs) Handles btnNewEmployee.Click
        Dim frmNewEmployee As NewEmployee = New NewEmployee()

        frmNewEmployee.ShowDialog()
    End Sub
End Class

In the Class Name combo box, select btnCalculate

In the Method Name combo box, select Click

Implement the event as follows:

Private Sub btnCalculateClick(ByVal sender As Object, 
            ByVal e As System.EventArgs) Handles btnCalculate.Click
        Dim LoanAmount As Double = 0.0
        Dim MonthlyPayment As Double = 0.0
        Dim InterestRate As Double = 0.0
        Dim Periods As Double = 0.0

        Try
            LoanAmount = CDbl(txtLoanAmount.Text)
        Catch ex As FormatException

            MsgBox("Invalid Loan Amount")
        End Try

        Try

            InterestRate = CDbl(txtInterestRate.Text)
        Catch ex As FormatException

            MsgBox("Invalid Interest Rate")
        End Try

        Try
            Periods = CDbl(txtPeriods.Text)
        Catch ex As FormatException

            MsgBox("Invalid Periods Value")
        End Try

        Try
            MonthlyPayment = Pmt( 
                   InterestRate / 12 / 100, 
                       Periods, 
                   -LoanAmount, 
                   0, 
               DueDate.BegOfPeriod)
            txtMonthlyPayment.Text = MonthlyPayment.ToString("F")
        Catch ex As FormatException
            MsgBox("Invalid Periods Value")
        End Try
End Sub

In the Class Name combo box, select (LoanPreparation Events)
In the Method Name combo box, select Load

Implement the Load event as follows:

Private Sub LoanPreparationLoad(ByVal sender As Object, 
                    ByVal e As System.EventArgs) Handles Me.Load
    Dim strDirectory As String = "C:\Watts A Loan"

    If Not Directory.Exists(strDirectory) Then
        Directory.CreateDirectory(strDirectory)

        Dim strFilename As String = strDirectory & "\Employees.wal"
        Dim fiEmployees As FileInfo = New FileInfo(strFilename)

        ' If the employees file was not created already,
        ' then create it
        If Not fiEmployees.Exists Then
            Dim stwEmployees As StreamWriter = fiEmployees.CreateText()

            ' And create a John Doe employee
            Try
                stwEmployees.WriteLine("00-000")
                stwEmployees.WriteLine("John Doe")
            Finally
                stwEmployees.Close()
            End Try
        End If
    End If
End Sub

In the Class Name combo box, select txtAccountNumber

In the Method Name combo box, select Leave and implement the event as follows:

Private Sub txtAccountNumberLeave(ByVal sender As Object, 
            ByVal e As System.EventArgs) Handles txtAccountNumber.Leave
    Dim strPath As String = "C:\Watts A Loan"

    Dim diLoans As DirectoryInfo = New DirectoryInfo(strPath)
    Dim aryLoans() As FileInfo = diLoans.GetFiles("*", 
     		SearchOption.AllDirectories)

    Dim strFilename As String = txtAccountNumber.Text & ".wal"
    Dim strFullname As String = strPath & "none.wal"
    Dim found As Boolean = False
    Dim fle As FileInfo

    For Each fle In aryLoans
        If fle.Name = strFilename Then
            found = True
            strFullname = fle.FullName
        End If
    Next

    If found = True Then
        Dim stmLoans As FileStream = File.Open(strFullname, 
                              FileMode.Open, 
                              FileAccess.Read)
        Dim bnrLoans As BinaryReader = New BinaryReader(stmLoans)

        txtAccountNumber.Text = bnrLoans.ReadString()
        txtCustomerName.Text = bnrLoans.ReadString()
        txtEmployeeNumber.Text = bnrLoans.ReadString()
        txtEmployeeName.Text = bnrLoans.ReadString()
        txtLoanAmount.Text = bnrLoans.ReadString()
        txtInterestRate.Text = bnrLoans.ReadString()
        txtPeriods.Text = bnrLoans.ReadString()
        txtMonthlyPayment.Text = bnrLoans.ReadString()

        bnrLoans.Close()
        stmLoans.Close()
    End If
End Sub

In the Class Name combo box, select txtEmployeeNumber
In the Method Name combo box, select Leave

Implement the event as follows:

Private Sub txtEmployeeNumberLeave(ByVal sender As Object, 
                ByVal e As System.EventArgs) 
			Handles txtEmployeeNumber.Leave
    Dim strFilename As String = "C:\Watts A Loan\Employees.wal"
    Dim fiEmployees As FileInfo = New FileInfo(strFilename)
    Dim line As String

    If fiEmployees.Exists Then
        If txtEmployeeNumber.Text = "" Then
            txtEmployeeName.Text = ""
            Exit Sub
        Else
            Dim stmEmployees As StreamReader = fiEmployees.OpenText()
            Dim strEmployeeNumber As String
            Dim strEmployeeName As String
            Dim found As Boolean

            strEmployeeNumber = ""
            found = False

            Try
                Do
                    line = stmEmployees.ReadLine()
                    If line = txtEmployeeNumber.Text Then
                        strEmployeeName = stmEmployees.ReadLine()
                        txtEmployeeName.Text = strEmployeeName
                        found = True
                    End If
                Loop Until line Is Nothing

                ' When the application has finished checking the file
                ' if there was no employee with that number, 
                ' let the user know
                If found = False Then
                    MsgBox("No employee with that number was found")
                    txtEmployeeName.Text = ""
                    txtEmployeeNumber.Focus()
                End If
            Finally
                stmEmployees.Close()
            End Try
        End If
    End If
End Sub

In the Class Name combo box, select btnSave

In the Method Name combo box, select Click

Implement the event as follows:

Private Sub btnSaveClick(ByVal sender As Object, 
                ByVal e As System.EventArgs) Handles btnSave.Click
        Dim strPath As String = "C:\Watts A Loan\" & 
                    txtAccountNumber.Text & ".wal"

        Dim stmLoan As FileStream = File.Create(strPath)
        Dim bnwLoan As BinaryWriter = New BinaryWriter(stmLoan)

        bnwLoan.Write(txtAccountNumber.Text)
        bnwLoan.Write(txtCustomerName.Text)
        bnwLoan.Write(txtEmployeeNumber.Text)
        bnwLoan.Write(txtEmployeeName.Text)
        bnwLoan.Write(txtLoanAmount.Text)
        bnwLoan.Write(txtInterestRate.Text)
        bnwLoan.Write(txtPeriods.Text)
        bnwLoan.Write(txtMonthlyPayment.Text)

        txtAccountNumber.Text = ""
        txtCustomerName.Text = ""
        txtEmployeeNumber.Text = ""
        txtEmployeeName.Text = ""
        txtLoanAmount.Text = ""
        txtInterestRate.Text = ""
        txtPeriods.Text = ""
        txtMonthlyPayment.Text = ""

        txtAccountNumber.Focus()

        bnwLoan.Close()
        stmLoan.Close()
End Sub

In the Class Name combo box, select btnClose

In the Method Name combo box, select Click

to the form and double-click the Close button to implement its event as follows:

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

Execute the application to test it

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

Process a few loans
Close the application


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