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 C++ 2005
To create a new application, on the main menu, click File -> New -> Project...
In the Templates list, click Windows Forms Application
Set the name to WattsALoan2
To be able to use the Visual Basic library, in the Solution Explorer, right-click WattsALoan1 and click References...
Click Add New Reference...
In the .NET property page, click Microsoft.VisualBasic
Click OK and OK
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

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

System::Void btnCalculate_Click(System::Object^  sender, 
				System::EventArgs^  e)
{
    double LoanAmount, InterestRate, Periods, MonthlyPayment;

    try {
	 LoanAmount = double::Parse(txtLoanAmount->Text);
    }
    catch(FormatException ^)
    {
	 MessageBox::Show(L"Invalid Loan Amount");
    }
				 
    try {
	 InterestRate = double::Parse(txtInterestRate->Text);
    }
    catch(FormatException ^)
    {
	 MessageBox::Show(L"Invalid Interest Rate");
    }
				 
    try {
	 Periods = double::Parse(txtPeriods->Text);
    }
    catch(FormatException ^)
    {
	 MessageBox::Show(L"Invalid Periods Value");
    }
				 
    try {
	 MonthlyPayment =
	     Microsoft::VisualBasic::Financial::Pmt(
			InterestRate / 12 / 100,
		        Periods,
			-LoanAmount,
			0 ,
		Microsoft::VisualBasic::DueDate::BegOfPeriod);
	 txtMonthlyPayment->Text = MonthlyPayment.ToString(L"F");
    }
    catch(FormatException ^)
    {
	 MessageBox::Show(L"Invalid Periods Value");
    }
}

Return to the form and double-click the Close button to implement its event as follows:
System::Void btnClose_Click(System::Object^ sender, System::EventArgs^ e) { Close(); }
Scroll up completely and, under the other using lines, type using namespace System::IO
To create a new form, on the main menu, click Project -> Add New Item...
In the Templates list, click Windows Form
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

Double-click the Close button
In the top section of the file, under the using using lines, type
using namespace System::IO;

Implement its event as follows:

System::Void btnClose_Click(System::Object^  sender, 
				System::EventArgs^  e)
{
	 Close();
}

Access the Form1 form
Double-click the New button
In the top section of the file, under the #pragma once line, type

#include "NewEmployee.h"

Scroll down and implement the event as follows:

System::Void btnNewEmployee_Click(System::Object^  sender, 
				  System::EventArgs^  e)
{
    NewEmployee ^ frmNewEmployee = gcnew NewEmployee;

    frmNewEmployee->ShowDialog();
}

Return to the form
On the (main) form, double-click an unoccupied area of its body

Implement its Load event as follows:

System::Void Form1_Load(System::Object^  sender, System::EventArgs^  e)
{
	 String ^ strDirectory = L"C:\\Watts A Loan";

	 if( !Directory::Exists(strDirectory) )
		 Directory::CreateDirectory(strDirectory);

	 String ^ strFilename = strDirectory + L"\\Employees.wal";

	 FileInfo ^ fiEmployees = gcnew FileInfo(strFilename);

	 // If the employees file was not created already,
	 // then create it
	 if( !fiEmployees->Exists )
	 {
	     StreamWriter ^ stwEmployees = fiEmployees->CreateText();

	     // And create a John Doe employee
	    try {
		 stwEmployees->WriteLine(L"00-000");
		 stwEmployees->WriteLine(L"John Doe");
	    }
	    finally
	    {
		 stwEmployees->Close();
	    }
	 }
}

Display the NewEmployee form and double-click its Create button

Implement its Click event as follows:

System::Void btnCreate_Click(System::Object^  sender, System::EventArgs^  e)
{
	 String ^ strFilename = L"C:\\Watts A Loan\\Employees.wal";
	 FileInfo ^ fiEmployees = gcnew FileInfo(strFilename);
	 StreamWriter ^ stwEmployees = nullptr;

	 // Normally, we should have the file already but just in case...
	 if( !fiEmployees->Exists )
		 stwEmployees = fiEmployees->CreateText();
	 else // If the file exists already, then we will only add to it
		 stwEmployees= fiEmployees->AppendText();
				 
	 try {
		 stwEmployees->WriteLine(txtEmployeeNumber->Text);
		 stwEmployees->WriteLine(txtEmployeeName->Text);
	 }
	 finally
	 {
		 stwEmployees->Close();
	 }

	 txtEmployeeNumber->Text = L"";
	 txtEmployeeName->Text = L"";
	 txtEmployeeNumber->Focus();
}

Return to the (main) form

In the combo box on top of the Properties window, select txtAccountNumber

In the Events section, double-click Leave and implement the event as follows:

System::Void txtAccountNumber_Leave(System::Object^  sender, 
				System::EventArgs^  e)
{
    String ^ strPath = L"C:\\Watts A Loan";

    DirectoryInfo ^ diLoans =
         gcnew DirectoryInfo(strPath);
    array<FileInfo ^> ^ aryLoans = diLoans->GetFiles(L"*",
		SearchOption::AllDirectories);

    String ^ strFilename = txtAccountNumber->Text + L".wal";
	String ^ strFullname = strPath + L"none.wal";
    bool found = false;

    for each(FileInfo ^ fle in aryLoans)
    {
        if( fle->Name == strFilename )
        {
            found = true;
            strFullname = fle->FullName;
        }
    }

    if( found == true )
    {
        FileStream ^ stmLoans =
			File::Open(strFullname,
                        FileMode::Open,
                        FileAccess::Read);
        BinaryReader ^ bnrLoans = gcnew 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();
    }
}

In the combo box on top of the Properties window, select txtEmployeeNumber
On the Properties window, click the Events button and double-click Leave

Implement the event as follows:

System::Void txtEmployeeNumber_Leave(System::Object^  sender, 
					System::EventArgs^  e)
{
    String ^ strFilename = L"C:\\Watts A Loan\\Employees.wal";
    FileInfo ^ fiEmployees = gcnew FileInfo(strFilename);

    if(fiEmployees->Exists )
    {
	 if( txtEmployeeNumber->Text == L"" )
	 {
		 txtEmployeeName->Text = L"";
		 return;
	 }
	 else
	 {
            StreamReader ^ strEmployees = fiEmployees->OpenText();
	    String ^ strEmployeeNumber, ^ strEmployeeName;
	    bool found = false;

	    try {
		 while( strEmployeeNumber = strEmployees->ReadLine() )
		 {
	  	     if( strEmployeeNumber == txtEmployeeNumber->Text )
		     {
			 strEmployeeName   = strEmployees->ReadLine();
			 txtEmployeeName->Text = strEmployeeName;
			 found = true;
		     }
		 }

		 // When the application has finished checking the file
		 // if there was no employee with that number, 
		 // let the user know
		 if( found == false )
		 {
		 MessageBox::Show(L"No employee with that number was found");
			 txtEmployeeName->Text = L"";
			 txtEmployeeNumber->Focus();
		 }
	    }
	    finally
	    {
		 strEmployees->Close();
	    }
	 }
    }
}

Return to the form and double-click the Save button

Implement the event as follows:

System::Void btnSave_Click(System::Object^  sender, System::EventArgs^  e)
{
    String ^ strPath =
	 L"C:\\Watts A Loan\\" + txtAccountNumber->Text + L".wal";

    FileStream ^ stmLoan = File::Create(strPath);
    BinaryWriter ^ bnwLoan =
                gcnew 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 = L"";
    txtCustomerName->Text = L"";
    txtEmployeeNumber->Text = L"";
    txtEmployeeName->Text = L"";
    txtLoanAmount->Text = L"";
    txtInterestRate->Text = L"";
    txtPeriods->Text = L"";
    txtMonthlyPayment->Text = L"";

    txtAccountNumber->Focus();

    bnwLoan->Close();
    stmLoan->Close();
}

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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