Microsoft Visual C++/CLI - Example Application: Simple Interest

	Example Application: Simple Interest

Introduction

This application shows how to calculate the interest accumulated on a loan and the total value that will paid at the end of the loan.

Practical Learning: Creating the Application

To start a new application, on the main menu, click File -> New -> Project
In the middle list, click Windows Application and change the Name to SimpleInterest1
Click OK
If the Resource View is not visible, on the main menu, click View -> Other Windows -> Resource View.
In the Resource View, right-click the name of the project -> Add -> Resource...
In the Add Resource dialog box, click Icon
Click New
Design the icon as follows:
Right-click 32x32, 4 bit, BMP and click Delete Image Type
Design the icon as follows:
Right-click 32x32, 4 bit, BMP and click Delete Image Type
Save all

Access the form and design it as follows:

Control	Text	Name	Other Properties
GroupBox	&Loan Preparation
Label	&Principal
TextBox	0.00	txtPrincipal	TextAlign: Right
Label	Interest &Rate:
TextBox	0.00	txtInterestRate	TextAlign: Right
Label	%
Label	Perio&ds:
TextBox	1	txtPeriods	TextAlign: Right
Label	Months
Button	C&alculate	btnCalculate	ImageAlign: TopCenter TextAlign: BottomCenter
Button	&Close	btnClose	ImageAlign: TopCenter TextAlign: BottomCenter
GroupBox	&Results
Label	Interest &Earned:
TextBox	0.00	txtInterestEarned	TextAlign: Right
Label	&Future Value
TextBox	0.00	txtFutureValue	TextAlign: Right

On the form, click the Calculate button
In the Properties window, click Image and click its ellipsis button
In the open dialog box, locate the SimpleInterest sub-folder inside the SimpleInterest folder of the current project
Select the icon that represents a calculator
Click Open
On the form, click the Close button
In the Properties window, click Image and click its ellipsis button
As done for the Calculate button, locate and select the other icon
Click Open

On the form, double-click the Calculate button and implement its Click event as follows:

System::Void btnCalculate_Click(System::Object^  sender,
				System::EventArgs^  e)
{
    double Principal    = 0.00,
           InterestRate = 0.00,
           InterestEarned,
           FutureValue;
    double Periods = 0.00;

    try {
        Principal = double::Parse(txtPrincipal->Text);
    }
    catch(FormatException ^)
    {
        MessageBox::Show(L"The value you entered for the "
                         L"principal is not valid");
    }

    try {
        InterestRate = double::Parse(txtInterestRate->Text);
    }
    catch(FormatException ^)
    {
        MessageBox::Show(L"Wrong Value: The interest rate must "
                         L"be a value between 0 and 100");
    }

    try {
        Periods = double::Parse(txtPeriods->Text);
    }
    catch(FormatException ^)
    {
        MessageBox::Show(L"You entered an invalid value for the periods");
    }

    double I = InterestRate / 100;
    double p = Periods / 12;
    
	InterestEarned = Principal * I  * p;
    FutureValue    = Principal + InterestEarned;

    txtInterestEarned->Text = InterestEarned.ToString(L"F");
    txtFutureValue->Text = FutureValue.ToString(L"F");
}

Return to the form and double-click the Close button

Implement its Click event as follows:

System::Void button1_Click(System::Object^  sender, System::EventArgs^  e)
{
	Close();
}

To execute the application, press F5
Enter 22580 for the principal, 12.75 for the interest rate, and 60 for the periods
Click Calculate
Close the form and return to your programming environment