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Example Application: Compounded Interest

   

Introduction to Radio Buttons

 

Description

The compounded interest is the amount of money paid as interest on a loan. This example uses some radio buttons to let the user select the frequency by which to perform the calculation.

   
Compound Interest Formula P = Principal
r = Annual (Interest) Rate
m = Number of Compounding Periods per Year
n = Total Number of Compounding Periods
A = Amount Earned After n periods
 

Application Application: Creating the Application

  1. Start a new Windows Application named CompoundedInterest
  2. Design the form as followed:
     
    Compound Interest - Form Design
    Control Name Text Additional Properties
    GroupBox GroupBox   Loan Setup  
    Label Label   Principal:  
    TextBox TextBox txtPrincipal 0.00 TextAlign: Right
    Label Label   Interest Rate:  
    TextBox TextBox txtInterestRate 8.25 TextAlign: Right
    Label Label   %  
    Label Label   Number of Periods:  
    TextBox TextBox txtPeriods 1 TextAlign: Text
    Label Label   years  
    GroupBox GroupBox   Compound Frequency  
    RadioButton RadioButton rdoMonthly    
    RadioButton RadioButton rdoQuarterly    
    RadioButton RadioButton rdoSemiannually    
    RadioButton RadioButton rdoAnnually    
    GroupBox GroupBox   Results  
    Label Label   Interest Earned:  
    TextBox TextBox txtInterestEarned 0.00 TextAlign: Right
    ReadOnly: True
    Label Label   Amount Earned:  
    TextBox TextBox txtFutureValue 0.00 TextAlign: Right
    ReadOnly: True
    Button Button btnCalculate Calculate  
    Button Button btnClose Close  
  3. On the form, double-click the Close button and implement its OnClick() event as follows:
    private void btnClose_Click(object sender, EventArgs e)
    {
                Close();
    }
  4. To test the application, press F5
  5. Close the form and return to your programming environment
  6. On the form, click Monthly
  7. In the Properties window, double-click Checked to set its value to True
  8. On the form, double-click the Calculate button and implement its Click() event as follows:
    private void btnCalculate_Click(object sender, EventArgs e)
    {
        double principal = 0.00,
               interestRate = 0.00,
               interestEarned = 0.00;
        double futureValue = 0.00,
               ratePerPeriod = 0.00,
               periods = 0;
        int compoundType = 0;
    
        // Retrieve the value of the principal
        principal = double.Parse(txtPrincipal.Text);
    
        // Retrieve the interest rate
        interestRate = double.Parse(txtInterestRate.Text) / 100;
    
        // Find out what radio button was clicked to apply the compound frequency
        if (rdoMonthly.Checked)
            compoundType = 12;
        else if (rdoQuarterly.Checked)
            compoundType = 4;
        else if (rdoSemiannually.Checked)
            compoundType = 2;
        else
            compoundType = 1;
    
        // Get the number of periods
        periods = double.Parse(txtPeriods.Text);
    
        // These values will make the calculation easier to read
        double i = interestRate / compoundType;
        double n = compoundType * periods;
    
        // Perform the necessary calculations
        ratePerPeriod = interestRate / periods;
        futureValue = principal * Math.Pow(1 + i, n);
        interestEarned = futureValue - principal;
    
        // Display the values in the appropriate text boxes
        txtInterestEarned.Text = interestEarned.ToString("C");
        txtFutureValue.Text = futureValue.ToString("C");
    }
  9. Test the application
     
    Compound Interest - Results
  10. After using it, close the form and return to your programming environment
 

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