Example Application: Simple Interest

	Example Application: Simple Interest

Description

This example explores the techniques of using the button control by adding bitmaps to them. The application is used to calculate the amount of interest accumulated on a loan.

Application: Using a Picture on a Button

Start Microsoft Visual Studio
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
On the main menu, click Project -> Add New Item...
In the middle list, click Icon File
Change the Name to Calculator and click OK
Right-click a white area in the icon designer -> Delete Image Type
Right-click the icon designer again -> Current Icon Image Types -> 16x16, 16 colors
Design the icon as follows:
On the main menu, click Project -> Add New Item...
In the middle list, click Icon File and change the Name to exit
Click Add
Right-click a white area in the icon designer -> Delete Image Type
Right-click the icon designer again -> Current Icon Image Types -> 16x16, 16 colors
Design the icon as follows:
Save and close the icon window
In the Solution Explorer, right-click Form1.cs and click Rename
Type SimpleInterest.cs and press Enter twice

Design the form as follows:

Control	Text	Name	TextAlign
GroupBox	Loan Preparation
Label	Principal
TextBox	0.00	txtPrincipal	Right
Label	Interest Rate:
TextBox	0.00	txtInterestRate	Right
Label	%
Label	Periods:
TextBox	1	txtPeriods	Right
Label	Months
Button	Calculate	btnCalculate
Button	Close	btnClose
GroupBox	Results
Label	Interest Earned:
TextBox	0.00	txtInterestEarned	Right
Label	Future Value
TextBox	0.00	txtFutureValue	Right

On the form, click the Calculate button
In the Properties window, click Image and click its ellipsis button
In the Select Resource dialog box, click Import
In the Files of Type box, select All Files
Locate the folder of the current project, select Calculator.ico and click Open
On the Select Resource dialog box, click OK
Change the following properties of the Calculate button:
ImageAlign: TopCenter
TextAlign: BottomCenter
On the form, click the Calculate button
In the Properties window, click Image and click its ellipsis button
In the Select Resource dialog box, click Import
In the Files of Type box, select All Files
Locate the folder of the current project, select exit.ico and click Open
On the Select Resource dialog box, click OK
Change the following properties of the Close button:
ImageAlign: TopCenter
TextAlign: BottomCenter

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

private void btnCalculate_Click(object sender, EventArgs e)
{
        decimal Principal    = 0.00M,
                    InterestRate = 0.00M,
                    InterestEarned,
                    FutureValue;
        decimal Periods = 0.00M;

        try
        {
                Principal = decimal.Parse(txtPrincipal.Text);
        }
        catch (FormatException)
        {
                MessageBox.Show("The value you entered for the " +
                                "principal is not valid");
        }

        try
        {
                InterestRate = decimal.Parse(txtInterestRate.Text);
        }
        catch (FormatException)
        {
                MessageBox.Show("Wrong Value: The interest rate must " +
                                "be a value between 0 and 100");
        }

        try
        {
                Periods = decimal.Parse(txtPeriods.Text);
        }
        catch (FormatException)
        {
                MessageBox.Show("You entered an invalid value for the periods");
        }

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

        txtInterestEarned.Text = InterestEarned.ToString("C");
        txtFutureValue.Text = FutureValue.ToString("C");
}

Return to the form
On the form, double-click the Close button and implement its Click event as follows:
```
private void btnClose_Click(object sender, EventArgs e)
{
            Close();
}
```
Execute the application and test the calculation
Close the form and return to your programming environment


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