Microsoft Visual C#: Data Binding With a Binding Source

private void btnBindingSource_Click(object sender, EventArgs e)
{
    BindingSource bsNames = new BindingSource();
    List<string> strNames = new List<string>();

    strNames.Add("Vicky Bisso");
    strNames.Add("Amy Warren");
    strNames.Add("Chrissie Childs");
    strNames.Add("Martial Otto");

    bsNames.DataSource = strNames;
    lbxNames.DataSource = bsNames;
}

After this assignment, the control can display the list.

In some cases, the list is not single. For example, you may already know that a data set can contain one or more tables and a table can contain one or more columns. In this case, you must specify the sub-list or column that holds the values that you want the control to display. To support this scenario, the singly list-based controls are equipped with a property named DisplayMember.

1. Create a new Windows Application named BethesdaCarRental3
2. In the Solution Explorer, right-click Form1.cs and click Rename
3. Type Central.cs and press Enter
4. Double-click the middle of the form and, to create the database including its tables, implement the event as follows:
   

   using System;
   using System.Collections.Generic;
   using System.ComponentModel;
   using System.Data;
   using System.Drawing;
   using System.Linq;
   using System.Text;
   using System.Windows.Forms;
   using System.Data.SqlClient;
   
   namespace BethesdaCarRental3a
   {
       public partial class Central : Form
       {
   	public Central()
   	{
   	    InitializeComponent();
   	}
   
   	void CreateDatabase()
   	{
   	    using (SqlConnection conBCR =
   		new SqlConnection("Data Source=(local); " +
   				  "Integrated Security='SSPI';"))
   	    {
   		string strCreateDatabase = "IF EXISTS ( " +
   		    "SELECT name " +
   		    "FROM sys.databases " +
   		    "WHERE name = N'BethesdaCarRental2' " +
   		    ") " +
   		    "DROP DATABASE BethesdaCarRental2; " +
   		    "CREATE DATABASE BethesdaCarRental2";
   
   		SqlCommand cmdBCR = 
   		    new SqlCommand(strCreateDatabase, conBCR);
   
   		conBCR.Open();
   		cmdBCR.ExecuteNonQuery();
   
   		MessageBox.Show("A database named " +
   				"BethesdaCarRental2 has been created");
   	    }
   
   	    using (SqlConnection conBCR =
   		new SqlConnection("Data Source=(local); " +
   			"Database='BethesdaCarRental2'; " +
   			"Integrated Security='SSPI';"))
   	    {
   		string strCreateTable = "CREATE TABLE RentalRates( " +
   			"RentalRateID int identity(1, 1) NOT NULL, " +
   			"Category varchar(50), " +
   			"Daily smallmoney, Weekly smallmoney, " +
   			"Monthly smallmoney, Weekend smallmoney, " +
   		"CONSTRAINT PK_RentalRates PRIMARY KEY (RentalRateID));";
   
   		SqlCommand cmdBCR = new SqlCommand(strCreateTable, conBCR);
   
   		conBCR.Open();
   		cmdBCR.ExecuteNonQuery();
   		MessageBox.Show("A table named RentalRates has been " +
   			"added to the BethesdaCarRental2 database.");
   	    }
   
   	    using (SqlConnection conBCR =
   		new SqlConnection("Data Source=(local); " +
   				  "Database='BethesdaCarRental2'; " +
   				  "Integrated Security='SSPI';"))
   	    {
   		string strCreateTable = "CREATE TABLE Employees( " +
   			"EmployeeID int identity(1, 1) NOT NULL, " +
   			"EmployeeNumber nchar(5), " +
   			"FirstName varchar(32), " +
   			"LastName varchar(32) NOT NULL, " +
   			"FullName AS (([LastName]+', ')+[FirstName]), " +
   			"Title varchar(80), " +
   			"HourlySalary smallmoney, " +
   			"CONSTRAINT PK_Employees PRIMARY KEY (EmployeeID));";
   
   		SqlCommand cmdBCR = new SqlCommand(strCreateTable, conBCR);
   
   		conBCR.Open();
   		cmdBCR.ExecuteNonQuery();
   		MessageBox.Show("A table named Employees has been " +
   			"added to the BethesdaCarRental2 database.");
   	    }
   
   	    using (SqlConnection conBCR =
   		new SqlConnection("Data Source=(local); " +
   			"Database='BethesdaCarRental2'; " +
   			"Integrated Security='SSPI';"))
   	    {
   		string strCreateTable = "CREATE TABLE Customers( " +
   			"CustomerID int identity(1, 1) NOT NULL, " +
   			"DrvLicNumber varchar(50), " +
   			"FullName varchar(80), " +
   			"Address varchar(100) NOT NULL, " +
   			"City varchar(50), " +
   			"State varchar(50), " +
   			"ZIPCode varchar(20), " +
   		    "CONSTRAINT PK_Customer PRIMARY KEY (CustomerID));";
   
   		SqlCommand cmdBCR = new SqlCommand(strCreateTable, conBCR);
   
   		conBCR.Open();
   		cmdBCR.ExecuteNonQuery();
   		MessageBox.Show("A table named Customers has been " +
   				"added to the BethesdaCarRental2 database.");
   	    }
   
   	    using (SqlConnection conBCR =
   		new SqlConnection("Data Source=(local); " +
   			"Database='BethesdaCarRental2'; " +
   			"Integrated Security='SSPI';"))
   	    {
   		string strCreateTable = "CREATE TABLE Cars( " +
   			"CarID int identity(1, 1) NOT NULL, " +
   			"TagNumber varchar(20), " +
   			"Make varchar(50), " +
   			"Model varchar(50) NOT NULL, " +
   			"CarYear smallint, " +
   			"Category varchar(50), " +
   			"CDPlayer bit, " +
   			"DVDPlayer bit, " +
   			"Available bit, " +
   			"CONSTRAINT PK_Car PRIMARY KEY (CarID));";
   
   		SqlCommand cmdBCR = 
   		    new SqlCommand(strCreateTable, conBCR);
   
   		conBCR.Open();
   		cmdBCR.ExecuteNonQuery();
   		MessageBox.Show("A table named Cars has been " +
   			    "added to the BethesdaCarRental2 database.");
   	    }
   
   	    using (SqlConnection conBCR =
   		new SqlConnection("Data Source=(local); " +
   			"Database='BethesdaCarRental2'; " +
   			"Integrated Security='SSPI';"))
   	    {
   		string strCreateTable = "CREATE TABLE RentalOrders( " +
   			"RentalOrderID int identity(1, 1) NOT NULL, " +
   			"DateProcessed datetime, " +
   			"EmployeeID int Constraint " +
   			"FK_Employees References " +
   			"Employees(EmployeeID) NOT NULL, " +
   			"EmployeeName varchar(80), " +
   			"CustomerID int Constraint " +
   			"FK_Customers References " +
   			"Customers(CustomerID) NOT NULL, " +
   			"CustomerName varchar(80), " +
   			"CustomerAddress varchar(100), " +
   			"CustomerCity varchar(50), " +
   			"CustomerState varchar(50), " +
   			"CustomerZIPCode varchar(20), " +
   			"CarID int Constraint " +
   			"FK_Cars References Cars(CarID) NOT NULL, " +
   			"CarMake varchar(50), " +
   			"CarModel varchar(50), " +
   			"CarYear smallint, " +
   			"CarCondition varchar(50), " +
   			"TankLevel varchar(40), " +
   			"MileageStart int, " +
   			"MileageEnd int, " +
   			"RentStartDate datetime, " +
   			"RentEndDate datetime, " +
   			"Days int, " +
   			"RateApplied money, " +
   			"SubTotal money, " +
   			"TaxRate decimal(6, 2), " +
   			"TaxAmount money, " +
   			"OrderTotal money, " +
   			"OrderStatus varchar(50), " +
   			"CONSTRAINT PK_RentalOrder " +
   			"PRIMARY KEY (RentalOrderID));";
   
   	    	SqlCommand cmdBCR = new SqlCommand(strCreateTable, conBCR);
   
   	    	conBCR.Open();
   	    	cmdBCR.ExecuteNonQuery();
   	    	MessageBox.Show("A table named RentalOrder has been " +
   	 		      "added to the BethesdaCarRental2 database.");
   	    }
       	}
   
   	private void Central_Load(object sender, EventArgs e)
   	{
   	    CreateDatabase(); 
   	}
       }
   }

5. Execute the application to actually create the database and its tables
6. Close the form and return to your programming environment
7. To create a new form, on the main menu, click Project -> Add Windows Form...
8. Set the name to Employees and click Add
9. To create a data source, on the main menu, click Data -> Add New Data Source...
10. In the first page of the wizard, make sure Database is selected and click Next
11. In the combo box
    • If you see a BethesdaCarRental2, select it
    • If you do not have BethesdaCarRental2, click New Connection... In the Server combo box, select the server or type (local). In the Select Or Enter A Database Name combo box, select BethesdaCarRental2. Click Test Connection. Click OK twice. In the Data Source Configuration Wizard, make sure the new connection is selected and click Next. Change the Connection String to csBethesdaCarRental and click Next. Expand the Tables node and expand the Employees node. Click the check boxes of EmployeeID, EmployeeNumber, FirstName, LastName, Title, and HourlySalary. Change the DataSet Name to dsBethesdaCarRental
       
      
12. Click Finish
13. In the Data Sources window, click Employees and click the arrow of its combo box to select DataGridView (it should be selected already as the default).
    Drag the Employees node and drop it on the form
14. Under the form, click the objects and, using the Properties window, change their names as follows:
     

    Object	Name
    employeesBindingSource	bsEmployees
    employeesTableAdapter	taEmployees
    employeesBindingNavigator	bnEmployees

15. On the form, click the data grid view control and, in the Properties window, change its (Name) to dgvEmployees
16. Click the ellipsis of the Columns field and make the following changes:
     

    Selected Columns	HeaderText	Width
    EmployeeID	Empl ID	50
    EmployeeNumber	Empl #	50
    FirstName	First Name	65
    LastName	Last Name	65
    Title		120
    HourlySalary	Hourly Salary	75

17. Click OK
18. Set DataGridView's Anchor property to Top, Bottom, Left, Right
19. Under the DataGridView control, add a button and set its properties as follows:
    Text: Close
    (Name): btnClose
    Anchor: Bottom, Right
     
    
20. Double-click the Close button and implement its even as follows:
    

    private void btnClose_Click(object sender, EventArgs e)
    {
         Close();
    }

21. Access the Central.cs [Design] tab
22. Add a button to it and set its properties as follows:
    Text: Employees
    (Name): btnEmployees
23. Double-click the Employees button and implement its even as follows:
    

    private void Central_Load(object sender, EventArgs e)
    {
        // CreateDatabase(); 
    }
    
    private void btnEmployees_Click(object sender, EventArgs e)
    {
        Employees clerks = new Employees();
        clerks.ShowDialog();
    }

24. Execute the application to test it
25. Click the Employees button and create the following records:
     

    Empl #	First Name	Last Name	Title	Hourly Salary
    20725	Julie	Flanell	Regional Manager	36.55
    92705	Paulette	Simms	Sales Manager	26.65
    84002	Alexandra	Ulm	Sales Representative	12.85
    47295	Ellie	Tchenko	Sales Representative	11.95

     
    
26. Close the forms and return to your programming environment
27. To create a new form, on the main menu, click Project -> Add Windows Form...
28. Set the name to Customers and click Add
29. In the Data Sources window, right-click dsBethesdaCaRental and click Configure Dataset with Wizard...
30. Expand the Tables node and click the check box of Customers
31. Click Finish
32. In the Data Sources window, drag Customers and drop it on the form
33. Under the form, click the objects and, using the Properties window, change their names as follows:
     

    Object	Name
    customersBindingSource	bsCustomers
    customersTableAdapter	taCustomers
    customersBindingNavigator	bnCustomers

34. On the form, click the data grid view control and, in the Properties window, change its (Name) to dgvCustomers
35. Click the ellipsis of the Columns field and make the following changes:
     

    Selected Columns	HeaderText	Width
    CustomerID	Cust ID	50
    DrvLicNumber	Driver's Lic #	80
    FullName	Full Name	120
    Address		120
    City		120
    State		40
    ZIPCode	ZIP Code	60

36. Click OK
37. Set DataGridView's Anchor property to Top, Bottom, Left, Right
38. Under the DataGridView control, add a button and set its properties as follows:
    Text: Close
    (Name): btnClose
    Anchor: Bottom, Right
     
    
39. Double-click the Close button and implement its even as follows:
    

    private void btnClose_Click(object sender, EventArgs e)
    {
         Close();
    }

40. Access the Central.cs [Design] tab
41. Add a button to it and set its properties as follows:
    Text: Customers
    (Name): btnCustomers
42. Double-click the Employees button and implement its even as follows:
    

    private void btnCustomers_Click(object sender, EventArgs e)
    {
        Customers clients = new Customers();
        clients.ShowDialog();
    }

43. Execute the application to test it
44. Click the Customers button and create Create a few records
45. Close the forms and return to your programming environment
46. To create a new form, on the main menu, click Project -> Add Windows Form...
47. Set the name to Cars and click Add
48. In the Data Sources window, right-click dsBethesdaCaRental and click Configure Dataset with Wizard...
49. Expand the Tables node and click the check box of Cars
50. Click Finish
51. In the Data Sources window, drag Cars and drop it on the form
52. Under the form, click the objects and, using the Properties window, change their names as follows:
     

    Object	Name
    carsBindingSource	bsCars
    carsTableAdapter	taCars
    carsBindingNavigator	bnCars

53. On the form, click the data grid view control and, in the Properties window, change its (Name) to dgvCars
54. Click the ellipsis of the Columns field and make the following changes:
     

    Selected Columns	HeaderText	Width
    CarID	Car ID	50
    TagNumber	Tag #	70
    Make		80
    Model		80
    CarYear	Year	50
    Category		80
    CDPlayer	CD Player	65
    DVDPlayer	DVD Player	70
    Available		65

55. Click OK
56. Set DataGridView's Anchor property to Top, Bottom, Left, Right
57. Under the DataGridView control, add a button and set its properties as follows:
    Text: Close
    (Name): btnClose
    Anchor: Bottom, Right
     
    
58. Double-click the Close button and implement its even as follows:
    

    private void btnClose_Click(object sender, EventArgs e)
    {
         Close();
    }

59. Access the Central.cs [Design] tab
60. Add a button to it and set its properties as follows:
    Text: Cars
    (Name): btnCars
61. Double-click the Employees button and implement its even as follows:
    

    private void btnCars_Click(object sender, EventArgs e)
    {
        Cars vehicles = new Cars();
        vehicles.ShowDialog();
    }

62. Execute the application to test it
63. Click the Cars button and create Create a few records
     
    
64. Close the forms and return to your programming environment
65. To add a new form to the project, on the main menu, click Project -> Add -> Windows Form...
66. Set the Name to RentalRates and press Enter
67. In the Data Sources window, right-click dsBethesdaCaRental and click Configure Dataset with Wizard...
68. Expand the Tables node and click the check box of RentalRates
69. Click Finish
70. In the Data Sources window, drag RentalRates and drop it on the form
71. Under the form, click the objects and, using the Properties window, change their names as follows:
     

    Object	Name
    rentalRatesBindingSource	bsRentalRates
    rentalRatesTableAdapter	taRentalRates
    rentalRatesBindingNavigator	bnRentalRates

72. On the form, click the data grid view control and, in the Properties window, change its (Name) to dgvRentalRates
73. Click the ellipsis of the Columns field and make the following changes:
     

    Selected Columns	HeaderText	Width
    RentalRateID	Rate ID	50
    Category		75
    Daily		50
    Weekly		50
    Monthly		50
    Weekend		50

74. Click OK
75. To create a new form, on the main menu, click Project -> Add Windows Form...
76. Set the name to OrderProcessing and click Add
77. In the Data Source window, right-click dsBethesdaCarRental and click Configure DataSet With Wizard...
78. Expand the Tables node and click the check box of RentalOrders and click Finish
79. In the Data Sources window, click RentalOrders and click the arrow of its combo box
80. Select Details
81. From the Data Sources window, drag RentalOrders and drop it on the form
82. Under the form, click the objects and, using the Properties window, change their names as follows:
     

    Object	Name
    rentalOrdersBindingSource	bsRentalOrders
    rentalOrdersTableAdapter	taRentalOrders
    rentalOrdersBindingNavigator	bnRentalOrders

83. Again, from the Data Sources window, drag Employees and drop it on the form
84. While the DataGridView control is still selected on the form, press Delete to remove it from the form
85. Under the form, click the objects and, using the Properties window, change their names as follows:
     

    Object	Name
    employeesBindingSource	bsEmployees
    employeesTableAdapter	taEmployees

86. From the Data Sources window, drag Customers and drop it in an empty area of the form
87. While the DataGridView control is still selected on the form, press Delete to remove it from the form
88. Under the form, click the objects and, using the Properties window, change their names as follows:
     

    Object	Name
    customersBindingSource	bsCustomers
    customersTableAdapter	taCustomers

89. Once again, from the Data Sources window, drag Cars and drop it on the form
90. While the DataGridView control is still selected on the form, press Delete to remove it from the form
91. Under the form, click the objects and, using the Properties window, change their names as follows:
     

    Object	Name
    carsBindingSource	bsCars
    carsTableAdapter	taCars

92. On the form, delete the text boxes on the right side of EmployeeID, CustomerID, CarID, CarCondition, TankLevel, and OrderStatus
93. Design the form as follows (you will add new controls to replace those that were deleted):
     

    Control Old Name  Text Name Additional Properties Label New Processed By:   BackColor: Gray BorderStyle: FixedSingle Label Old Employee #:     ComboBox New   cboEmployeeID   TextBox  employeeNameTextBox    txtEmployeeName   Label   Processing For   BackColor: Gray BorderStyle: FixedSingle  Label  Old  Driver's Lic. #:     ComboBox New   cbxCustomerID   Label Old  Customer Name:     TextBox customerNameTextBox   txtCustomerName   Label Old  Address:     TextBox customerAddressTextBox   txtCustomerAddress   Label Old  City:     TextBox customerCityTextBox   txtCustomerCity   Label Old  State:     TextBox customerStateTextBox   txtCustomerState   Label Old  ZIP Code:     TextBox customerZIPCodeTextBox   txtCustomerZIPCode   Label  New Car Selected   BackColor: Gray BorderStyle: FixedSingle  Label Old Tag Number:     ComboBox New   cbxCarID   Label Old Car Condition:     ComboBox New   cbxCarConditions Items: Needs Repair Drivable Excellent Label  Old Make:     TextBox carMakeTextBox   txtCarMake   Label    Model:     TextBox carModelTextBox   txtCarModel   Label  Old Year:      TextBox Old    txtCarYear   Label Old Tank Level:     ComboBox New   cbxTankLevels Items: Empty 1/4 Empty 1/2 Full 3/4 Full Full  Label  Old Mileage Start:     TextBox mileageStartTextBox    txtMileageStart TextAlign: Right   Label   Mileage End:     TextBox mileageEndTextBox   txtMileageEnd TextAlign: Right Label    Order Timing   BackColor: Gray BorderStyle: FixedSingle  Label Old  Date Processed     DateTimePicker dateProcessedDateTimePicker   dtpDateProcessed   Label Old  Rent Start Date:     DateTimePicker rentStartDateDateTimePicker     dtpRentStartDate   Label   Rent End Date:     DateTimePicker rentEndDateDateTimePicker     dtpRentEndDate   Label Old  Total Days:     TextBox daysTextBox   txtTotalDays   Label   Order Evaluation   BackColor: Gray BorderStyle: FixedSingle  Label Old  Rate Applied     TextBox rateAppliedTextBox   txtRateApplied TextAlign: Right Button New Rental Rates btnRentalRates    Label Old  Sub Total:      TextBox subTotalTextBox   txtSubTotal TextAlign: Right Button  New Calculate btnCalculate   Label Old Tax Rate:     TextBox taxRateTextBox   txtTaxRate TextAlign: Right Label   %     Label   Tax Amount:     TextBox taxAmountTextBox    txtTaxAmount TextAlign: Right Label   Order Total:     TextBox orderTotalTextBox    txtOrderTotal TextAlign: Right Label  Old Order Status:     ComboBox  New   cbxOrderStatus Items: Car On Road Car Returned Order Reserved  Label  Old Rental Order ID:     TextBox rentalOrderIDTextBox    txtRentalOrderID TextAlign: Right  Button   Close btnClose   StatusStrip

94. Click each control that was added and change its data bindings
95. On the form, double-click the Employee # combo box and implement its Click event as follows:
    

    private void cbxEmployeeID_SelectedIndexChanged(object sender, EventArgs e)
    {
        using (System.Data.SqlClient.SqlConnection conEmployees =
    	new System.Data.SqlClient.SqlConnection("Data Source=(local);" +
    						"Database=BethesdaCarRental2;" +
    						"Integrated Security=yes"))
       {
    	string strEmployee = "SELECT FullName FROM Employees " +
    			     "WHERE EmployeeNumber = '" +
    			      cbxEmployeeID.Text + "';";
    
    	System.Data.SqlClient.SqlCommand cmdEmployees =
    		new System.Data.SqlClient.SqlCommand(strEmployee, conEmployees);
    	conEmployees.Open();
    
    	System.Data.SqlClient.SqlDataReader rdrEmployees =
    		cmdEmployees.ExecuteReader();
    
    	while (rdrEmployees.Read())
    	    txtEmployeeName.Text = rdrEmployees.GetString(0);
        }
    }

96. Return to the OrderProcessing form
97. On the form, double-click the Driver's Lic # combo box and implement its Click event as follows:
    

    private void cbxCustomerID_SelectedIndexChanged(object sender, EventArgs e)
    {
        using (System.Data.SqlClient.SqlConnection conCustomers =
    	new System.Data.SqlClient.SqlConnection("Data Source=(local);" +
    					"Database=BethesdaCarRental2;" +
    						"Integrated Security=yes"))
        {
    	string strCustomer = "SELECT * FROM Customers " +
    			     "WHERE DrvLicNumber = '" +
    			     cbxCustomerID.Text + "';";
    
    	System.Data.SqlClient.SqlCommand cmdCustomers =
    	    new System.Data.SqlClient.SqlCommand(strCustomer, conCustomers);
    	conCustomers.Open();
    
    	System.Data.SqlClient.SqlDataReader rdrCustomers = 
    		cmdCustomers.ExecuteReader();
    
    	while (rdrCustomers.Read())
    	{
    	    txtCustomerName.Text = rdrCustomers.GetString(2);
    	    txtCustomerAddress.Text = rdrCustomers.GetString(3);
    	    txtCustomerCity.Text = rdrCustomers.GetString(4);
    	    txtCustomerState.Text = rdrCustomers.GetString(5);
    	    txtCustomerZIPCode.Text = rdrCustomers.GetString(6);
    	}
        }
    }

98. Return to the OrderProcessing form
99. On the form, double-click the Tag Number combo box and implement its Click event as follows:
    

    private void cbxCarID_SelectedIndexChanged(object sender, EventArgs e)
    {
        using (System.Data.SqlClient.SqlConnection conCars =
    	new System.Data.SqlClient.SqlConnection("Data Source=(local);" +
    	    "Database=BethesdaCarRental2;" +
    	    "Integrated Security=yes"))
       {
    	string strCar = "SELECT * FROM Cars " +
    		        "WHERE TagNumber = '" +
    			cbxCarID.Text + "';";
    
    	System.Data.SqlClient.SqlCommand cmdCars =
    	    new System.Data.SqlClient.SqlCommand(strCar, conCars);
    	conCars.Open();
    
    	System.Data.SqlClient.SqlDataReader rdrCars =
    	    cmdCars.ExecuteReader();
    
    	while (rdrCars.Read())
    	{
    	    txtCarMake.Text = rdrCars.GetString(2);
    	    txtCarModel.Text = rdrCars.GetString(3);
    	    txtCarYear.Text = rdrCars.GetSqlInt16(4).ToString();
    	}
        }
    }

100. Return to the OrderProcessing form
101. On the form, double-click the Rent End Date control and implement the event as follows:
     

     private void dtpRentEndDate_ValueChanged(object sender, EventArgs e)
     {
         if( dtpRentStartDate.Value > dtpRentEndDate.Value )
     	txtTotalDays.Text = "0";
         else if (dtpRentStartDate.Value == dtpRendependDate.Value)
     	txtTotalDays.Text = "1";
         else
         {
     	int days;
     
     	DateTime dteStart = dtpRentStartDate.Value;
     	DateTime dteEnd = dtpRentEndDate.Value;
     
     	// Let's calculate the difference in days
     	TimeSpan tme = dteEnd - dteStart;
     	days = tme.Days;
     
     	// If the customer returns the car the same day, 
     	// we consider that the car was rented for 1 day
     	if (days == 0)
     	    days = 1;
     
     	txtTotalDays.Text = days.ToString();
     	// At any case, we will let the clerk specify the actual number of days
         }
     }

102. Return to the OrderProcessing form and double-click the Rental Rates button
103. Implement the event as follows:
     

     private void btnRentalRates_Click(object sender, EventArgs e)
     {
         RentalRates rates = new RentalRates();
         rates.ShowDialog();
     } 

104. Return to the OrderProcessing form and doouble-click the Calculate button
105. Implement the events as follows:
     

     private void btnCalculate_Click(object sender, EventArgs e)
     {
         int Days = 0;
         double RateApplied = 0.00;
         double TaxRate = 0.00;
         double SubTotal, TaxAmount, OrderTotal;
     
         try
         {
     	Days = int.Parse(txtTotalDays.Text);
         }
         catch (FormatException)
         {
     	MessageBox.Show("Invalid number of days.");
         }
     
         try
         {
     	RateApplied = double.Parse(txtRateApplied.Text);
         }
         catch (FormatException)
         {
     	MessageBox.Show("Invalid rate applied.");
         }
     
         try
         {
     	TaxRate = double.Parse(txtTaxRate.Text);
         }
         catch (FormatException)
         {
     	MessageBox.Show("Invalid tax rate.");
         }
     
         SubTotal = Days * RateApplied;
         TaxAmount = SubTotal * TaxRate / 100;
         OrderTotal = SubTotal + TaxAmount;
     
         txtSubTotal.Text = SubTotal.ToString("F");
         txtTaxAmount.Text = TaxAmount.ToString("F");
         txtOrderTotal.Text = OrderTotal.ToString("F");
     }

106. Return to OrderProcessing the form and double-click the Close button
107. Implement its even as follows:
     

     private void btnClose_Click(object  sender, EventArgs  e)
     {
         Close();
     }

108. Access the Central form
109. Add a button to it and set its properties as follows:
     Text: OrderProcessing
     (Name): btnOrderProcessing
110. Double-click the OrderProcessing button and implement the even as follows:
     

     private void btnOrderProcessing_Click(object sender, EventArgs e)
     {
         OrderProcessing frmOrder = new OrderProcessing();
         frmOrder.ShowDialog();
     }

111. Return to the Central form and double-click the Close button
112. Implement the event as follows:
     

     private void btnClose_Click(object sender, EventArgs e)
     {
         Close();
     }

113. Execute the application and display the OrderProcessing form
114. To create an order, click the + button, complete the form, and click the Save button. Here are examples:
      
115. Close the forms and return to your programming environment
116. Execute the application again and display the Order Processing form again
117. Click the Rental Rates button and create the values as follows:
      

     Category	Daily	Weekly	Monthly	Weekend
     Economy	35.95	32.75	28.95	24.95
     Compact	39.95	35.75	32.95	28.95
     Standard	45.95	39.75	35.95	32.95
     Full Size	49.95	42.75	38.95	35.95
     Mini Van	55.95	50.75	45.95	42.95
     SUV	55.95	50.75	45.95	42.95
     Truck	42.75	38.75	35.95	32.95
     Van	69.95	62.75	55.95	52.95

118. Update the orders you previously processed and save them
      
119. Close the forms and return to your programming environment