Loan Amortization Application in WPF

Lets going to make a simple WPF application to calculate the Loan Amortization schedule. Here is a XAML code to crate the user interface of the application.

  1: <Window x:Class="Amortization.Window1"

  2:     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

  3:     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

  4:     Title="Loan Amortization" Height="600" Width="800" Background="Wheat">

  5:     <Grid>

  6:         <Grid.RowDefinitions>

  7:             <RowDefinition/>

  8:             <RowDefinition/>

  9:             <RowDefinition/>

 10:             <RowDefinition Height="4*" />

 11:             <RowDefinition/>

 12:         </Grid.RowDefinitions>

 13:         

 14:         <Grid.ColumnDefinitions>

 15:             <ColumnDefinition/>

 16:             <ColumnDefinition/>

 17:         </Grid.ColumnDefinitions>

 18:         

 19:         <TextBlock Grid.Column="0" Grid.Row="0" Margin="5" VerticalAlignment="Center">

 20:             Principle Amount

 21:         </TextBlock>

 22: 

 23:         <TextBox Grid.Column="1" Grid.Row="0" Margin="5" Name="txtPrinciple" VerticalAlignment="Center">            

 24:         </TextBox>

 25:         

 26:         <TextBlock Grid.Column="0" Grid.Row="1" Margin="5" VerticalAlignment="Center">

 27:             Interest Rate

 28:         </TextBlock>

 29: 

 30:         <TextBox Grid.Column="1" Grid.Row="1" Margin="5" Name="txtInterest" VerticalAlignment="Center">

 31:         </TextBox>

 32: 

 33:         <TextBlock Grid.Column="0" Grid.Row="2" Margin="5" VerticalAlignment="Center">

 34:             No of years

 35:         </TextBlock>

 36: 

 37:         <TextBox Grid.Column="1" Grid.Row="2" Margin="5" Name="txtYears" VerticalAlignment="Center">

 38:         </TextBox>

 39: 

 40:         <ListBox Grid.Column="0" Grid.Row="3" Grid.ColumnSpan="2" 

 41:                  Name="lstAmortization" Background="Wheat" HorizontalContentAlignment="Stretch">

 42:             <ListBox.ItemTemplate>

 43:                 <DataTemplate>

 44:                     <Border Margin="5" Background="White" BorderBrush="Brown" BorderThickness="5" CornerRadius="10">

 45:                         <Grid>

 46:                             <Grid.RowDefinitions>

 47:                                 <RowDefinition/>

 48:                                 <RowDefinition/>

 49:                                 <RowDefinition/>

 50:                                 <RowDefinition/>

 51:                                 <RowDefinition/>

 52:                             </Grid.RowDefinitions>

 53:                             

 54:                             <Grid.ColumnDefinitions>

 55:                                 <ColumnDefinition/>

 56:                                 <ColumnDefinition/>

 57:                             </Grid.ColumnDefinitions>

 58:                             

 59:                             <TextBlock Grid.Row="0" Grid.Column="0" Margin="5">

 60:                                 Payment No

 61:                             </TextBlock>

 62:                             

 63:                             <TextBlock Grid.Row="0" Grid.Column="1" Margin="5, 0" Foreground="Blue" FontSize="12" Text="{Binding Path=PaymentNo}"/>

 64: 

 65:                             <TextBlock Grid.Row="1" Grid.Column="0" Margin="5, 0">

 66:                                 Payment

 67:                             </TextBlock>

 68: 

 69:                             <TextBlock Grid.Row="1" Grid.Column="1" Margin="5, 0" Foreground="Blue" FontSize="12" Text="{Binding Path=Payment}"/>

 70: 

 71:                             <TextBlock Grid.Row="2" Grid.Column="0" Margin="5, 0">

 72:                                 Principle

 73:                             </TextBlock>

 74: 

 75:                             <TextBlock Grid.Row="2" Grid.Column="1" Margin="5, 0" Foreground="Blue" FontSize="12" Text="{Binding Path=Principle}"/>

 76: 

 77:                             <TextBlock Grid.Row="3" Grid.Column="0" Margin="5, 0">

 78:                                 Interest

 79:                             </TextBlock>

 80: 

 81:                             <TextBlock Grid.Row="3" Grid.Column="1" Margin="5, 0" Foreground="Blue" FontSize="12" Text="{Binding Path=Interest}"/>

 82: 

 83:                             <TextBlock Grid.Row="4" Grid.Column="0" Margin="5, 0">

 84:                                 Balance

 85:                             </TextBlock>

 86: 

 87:                             <TextBlock Grid.Row="4" Grid.Column="1" Margin="5, 0" Foreground="Blue" FontSize="12" Text="{Binding Path=Balance}"/>

 88:                         </Grid>

 89:                     </Border>

 90:                 </DataTemplate>

 91:             </ListBox.ItemTemplate>        

 92:         </ListBox>

 93:         

 94:         <Button Grid.Column="0" Grid.Row="4" Grid.ColumnSpan="2" Width="75" Height="45" Name="btnCalculate" Click="btnCalculate_Click">

 95:             Calculate

 96:         </Button>

 97:     </Grid>

 98: </Window>

 99: 
This application will display the loan amortization schedule in list box. To display it in more user friendly way we use the data template with list box. 
Here is a C# code to perform all the calculation. 
  1: using System;

  2: using System.Collections.Generic;

  3: using System.Linq;

  4: using System.Text;

  5: using System.Windows;

  6: using System.Windows.Controls;

  7: using System.Windows.Data;

  8: using System.Windows.Documents;

  9: using System.Windows.Input;

 10: using System.Windows.Media;

 11: using System.Windows.Media.Imaging;

 12: using System.Windows.Navigation;

 13: using System.Windows.Shapes;

 14: 

 15: namespace Amortization

 16: {

 17:     /// <summary>

 18:     /// Interaction logic for Window1.xaml

 19:     /// </summary>

 20:     public partial class Window1 : Window

 21:     {

 22:         private int years;

 23:         private double interestRate;

 24:         private double principle;

 25:         private int totalPayments;

 26:         private double payment;

 27:         private double monthlyRate;

 28: 

 29:         public Window1()

 30:         {

 31:             InitializeComponent();

 32:         }

 33: 

 34:         private void btnCalculate_Click(object sender, RoutedEventArgs e)

 35:         {

 36:             years = Convert.ToInt32(txtYears.Text);

 37:             interestRate = Convert.ToDouble(txtInterest.Text) / 100;

 38:             principle = Convert.ToDouble(txtPrinciple.Text);

 39:             monthlyRate = interestRate / 12;

 40:             totalPayments = years * 12;

 41: 

 42:             calculatePayment();

 43:         }

 44: 

 45:         private void calculatePayment()

 46:         {

 47:             // calculate interest term

 48:             double interestTerm = Math.Pow((1 + monthlyRate), this.totalPayments);

 49: 

 50:             // calculate payment

 51:             this.payment = (this.principle * monthlyRate) / (1 - (1 / interestTerm));

 52: 

 53:             for (int iIndex = 1; iIndex <= totalPayments; ++iIndex)

 54:             {

 55:                 PaymentInfo paymentInfo = new PaymentInfo();

 56:                 paymentInfo.PaymentNo = iIndex;

 57:                 paymentInfo.Balance = calculateBalance(iIndex);

 58:                 paymentInfo.Payment = payment;

 59:                 paymentInfo.Interest = calculateInterestPart(iIndex);

 60:                 paymentInfo.Principle = calculatePrinciple(iIndex);

 61: 

 62:                 lstAmortization.Items.Add(paymentInfo);

 63:             }

 64:         }

 65: 

 66:         private double calculateBalance(int month)

 67:         {

 68:             double interestTerm = Math.Pow((1 + monthlyRate), month);

 69:             double totalInterest = this.principle * interestTerm;

 70:             double totalPaid = payment * (interestTerm - 1) / monthlyRate;

 71:             return totalInterest - totalPaid;

 72:         }

 73: 

 74:         private double calculateInterestPart(int month)

 75:         {

 76:             double interestTerm = Math.Pow((1 + monthlyRate), (month - 1));

 77:             double totalInterest = this.principle * interestTerm;

 78:             double totalPaid = payment * (interestTerm - 1) / monthlyRate;

 79:             return (totalInterest - totalPaid) * monthlyRate;

 80:         }

 81: 

 82:         private double calculatePrinciple(int month)

 83:         {

 84:             return payment - calculateInterestPart(month);

 85:         }

 86: 

 87: 

 88:     }

 89: 

 90:     class PaymentInfo

 91:     {

 92:         private int paymentNo;

 93:         private double payment;

 94:         private double principle;

 95:         private double interest;

 96:         private double balance;

 97: 

 98:         public int PaymentNo

 99:         {

100:             get { return paymentNo; }

101:             set { paymentNo = value; }

102:         }

103: 

104:         public double Payment

105:         {

106:             get { return payment; }

107:             set { payment = value; }

108:         }

109: 

110:         public double Principle

111:         {

112:             get { return principle; }

113:             set { principle = value; }

114:         }

115: 

116:         public double Interest

117:         {

118:             get { return interest; }

119:             set { interest = value; }

120:         }

121: 

122:         public double Balance

123:         {

124:             get { return balance; }

125:             set { balance = value; }

126:         }

127:     }

128: 

129: }

130: 
Here is the output of this program.