Introduction

This sample application reviews some of the ways you can assist the user with data entry. These include specify the right data type for a column, setting a default value, creating an expression, or controlling the nullity of a field.

The application is for a company that lends money, either cash or to purchase something (car, musical instrument, boat, bicycle, etc).

The records are save as XML

1. Start Microsoft Visual C# and create a Windows Application named WattsALoan4
2. To create a new form, in the Solution Explorer, right-click WattsALoan4 -> Add -> Windows Forms...
3. Set the Name to LoanAllocations and click Add
4. From the Data section of the Toolbox, click DataSet and click the form
5. Select the Untyped Dataset radio button and click OK
6. In the Properties window, change the following characteristics:
   DataSetName: dsLoanAllocations
   (Name): LoanAllocations
7. Click Tables and click its ellipsis button
8. To create a new table, click Add and change the properties as follows:
   TableName: Loan
   (Name): tblLoan
9. Click Columns and click its ellipsis button
10. Click Add 10 times and change the properties as follows:
     

    ColumnName	(Name)
    DateAllocated	colDateAllocated
    LoanNumber	colLoanNumber
    PreparedBy	colPreparedBy
    PreparedFor	colPreparedFor
    Principal	colPrincipal
    InterestRate	colInterestRate
    Periods	colPeriods
    InterestEarned	colInterestEarned
    FutureValue	colFutureValue
    MonthlyPayment	colMonthlyPayment

11. In the Members list, click LoanNumber
12. In the Properties list, double-click Unique to change its value to True
13. In the Members list, click Principal
14. In the Properties list, click DataType, click the arrow of its combo box and select System.Double
15. In the same way, change the data types of the following columns:
     

    Member	DataType
    DateAllocated	System.DateTime
    LoanNumber	System.String
    PreparedBy	System.String
    PreparedFor	System.String
    Principal	System.Double
    InterestRate	System.Double
    Periods	System.Double
    InterestEarned	System.Double
    FutureValue	System.Double
    MonthlyPayment	System.Double

16. In the Members list, click Principal
17. In the Properties list, click DefaultValue and delete <DBNull>
18. Type 0.00
19. In the same way, change the default values of the following columns:
     

    Member	DefaultValue
    Principal	0.00
    InterestRate	8.75
    Periods	36

20. In the Members list, click FutureValue
21. In the Properties list, click Expression and type Principal + InterestEarned
22. In the same way, change the data types of the following columns:
     

    Member	Expression
    InterestEarned	Principal * (InterestRate / 100) * (Periods / 12)
    FutureValue	Principal + InterestEarned
    MonthlyPayment	FutureValue / Periods

23. In the Members list, click DateAllocated
24. In the Properties list, double-click the value of the AllowDBNull field to set it to False
25. In the Members list, click LoanNumber
26. In the Properties list, double-click the value of the AllowDBNull field to set it to False
27. Click Close and click Close
28. To create a new form, in the Solution Explorer, right-click WattsALoan4 -> Add -> Windows Forms...
29. Set the Name to Employees and click Add
30. From the Data section of the Toolbox, click DataSet and click the form
31. Select the Untyped Dataset radio button and click OK
32. In the Properties window, change the following characteristics:
    DataSetName: dsEmployees
    (Name): Employees
33. Click Tables and click its ellipsis button
34. To create a new table, click Add and change the properties as follows:
    TableName: Employee
    (Name): tblEmployee
35. Click Columns and click its ellipsis button
36. Click Add 5 times and change the properties as follows:
     

    AllowDBNull	ColumnName	DefaultValue	DataType	Expression	Unique	(Name)
    False	EmployeeNumber				True	colEmployeeNumber
    	FirstName					colFirstName
    False	LastName					colLastName
    	FullName			LastName + ', ' + FirstName		colFullName
    	Title					colTitle
    	HourlySalary	8.75	System.Double			colHourlySalary

37. Click Close and click Close
38. Design the form as follows:
     

    Control Text Name Other Properties DataGridView   dgvEmployees DataSource: dsEmployees DataMember: Employee Button Close btnClose

    Data Grid Columns

    DataPropertyName HeaderText Width EmployeeNumber Empl # 65 FirstName First Name 65 LastName Last Name 65 FullName Full Name 120 Title   110 HourlySalary Salary/hr 60

39. Double-click an unoccupied area of the form and implement the event as follows:
     

    using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Text; using System.Windows.Forms; using System.IO; namespace WattsALoan4 { public partial class Employees : Form { public Employees() { InitializeComponent(); } private void Employees_Load(object sender, EventArgs e) { string strFilename = "employees.xml"; if (File.Exists(strFilename)) dsEmployees.ReadXml(strFilename); } } }

40. Return to the form and click an unoccupied area of its body
41. In the Properties window, click the Events button and double-click FormClosing
42. Implement the event as follows:
     

    private void Employees_FormClosing(object sender, FormClosingEventArgs e) { dsEmployees.WriteXml("employees.xml"); }

43. Return to the form and double-click the Close button
44. Implement the event as follows:
     

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

45. Return to the form
46. Under the form, right-click dsEmployees and click Copy
47. Display the LoanAllocations form
48. Right-click it and click Paste
49. To create a new form, in the Solution Explorer, right-click WattsALoan4 -> Add -> Windows Forms...
50. Set the Name to Customers and click Add
51. From the Data section of the Toolbox, click DataSet and click the form
52. Select the Untyped Dataset radio button and click OK
53. In the Properties window, change the following characteristics:
    DataSetName: dsCustomers
    (Name): Customers
54. Click Tables and click its ellipsis button
55. To create a new table, click Add and change the properties as follows:
    TableName: Customer
    (Name): tblCustomer
56. Click Columns and click its ellipsis button
57. Click Add 5 times and change the properties as follows:
     

    AllowDBNull	ColumnName	Unique	(Name)
    False	AccountNumber	True	colAccountNumber
    False	FullName		colFullName
    	EmailAddress		colEmailAddress
    	PhoneNumber		colPhoneNumber

58. Click Close and click Close
59. Design the form as follows:
     

    Control Text Name Other Properties DataGridView   dgvCustomers DataSource: dsCustomers DataMember: Customer Button Close btnClose

    Data Grid Columns

    DataPropertyName HeaderText Width AccountNumber Account # 65 FullName Full Name 120 EmailAddress Email Address 120 PhoneNumber Phone # 90

60. Double-click an unoccupied area of the form and implement the event as follows:
     

    using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Text; using System.Windows.Forms; using System.IO; namespace WattsALoan4 { public partial class Customers : Form { public Customers() { InitializeComponent(); } private void Customers_Load(object sender, EventArgs e) { string strFilename = "customers.xml"; if (File.Exists(strFilename)) dsCustomers.ReadXml(strFilename); } } }

61. Return to the form and click an unoccupied area of its body
62. In the Properties window, click the Events button and double-click FormClosing
63. Implement the event as follows:
     

    private void Customers_FormClosing(object sender, FormClosingEventArgs e) { dsCustomers.WriteXml("customers.xml"); }

64. Return to the form and double-click the Close button
65. Implement the event as follows:
     

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

66. Return to the form
67. Under the form, right-click dsCustomers and click Copy
68. Display the LoanAllocations form
69. Right-click it and click Paste
70. Design the form as follows: