1. 1 Web-Enabled Decision Support Systems Advance Topics in Database Connectivity Prof. Name name@email.com Position (123) 456-7890 University Name

2. 2 Overview  15.1 Introduction  15.2 ADO.NET Architecture  15.3 A Database Connection  15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters  15.5 Hands-On Tutorial: Displaying Data from Join of Tables  15.6 Hands-On Tutorial: Displaying Data Using Access Query  15.7 Hands-On Tutorial: Passing Data between Forms  15.8 DataSets  15.9 Inserts, Updates, and Deletes in a Windows Application  15.10 Hands-On Tutorial: Updating Changes to Multiple Tables  15.11 In-Class Assignment  15.12 Summary

3. 3 Introduction  In the previous chapter, we discussed basic database connectivity topics: –The Data Sources Window –Displaying information on Windows forms –Displaying data from related tables –Building search forms and look-up tables  Real life database applications are seldom so simple –Fortunately, Visual Studio provides a rich set of tools to develop professional applications efficiently –In this chapter, we will study advanced database connectivity topics

4. 4 Overview  15.1 Introduction  15.2 ADO.NET Architecture  15.3 A Database Connection  15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters  15.5 Hands-On Tutorial: Displaying Data from Join of Tables  15.6 Hands-On Tutorial: Displaying Data Using Access Query  15.7 Hands-On Tutorial: Passing Data between Forms  15.8 DataSets  15.9 Inserts, Updates, and Deletes in a Windows Application  15.10 Hands-On Tutorial: Updating Changes to Multiple Tables  15.11 In-Class Assignment  15.12 Summary

5. 5 ADO.NET Architecture  ActiveX Data Objects (ADO).NET is the collection of objects that are designed to support data access and data manipulation  Database connectivity involves the following entities: –Database  Stores data on the hard drive (disk) –Connection  Connects to the database –DataAdapter  Hosts SQL queries and executes them against the database –DataSet  Stores data in main memory –Form  Displays data to the user

6. 6 ADO.NET Architecture (cont.)  From database to Windows forms: 1.A Connection object opens a live connection to the database 2.A DataAdapter object executes Select SQL queries against the database 3.The DataAdapter object further fills a DataSet object with query results  The DataSet stores the results in the main memory 4.DataSets are associated with various Windows controls on a form  This association is referred to as Data Binding  Data binding makes it possible for the query results in the DataSet to be displayed on a form for the user ADO.NET Architecture

7. 7 ADO.NET Architecture (cont.)  From Windows forms to database: 1.If a user edits the data in Windows controls, the updates are propagated to the DataSet object 2.The DataAdapter object then propagates the updates from the DataSet object to the connected database by executing Update SQL statements

8. 8 Overview  15.1 Introduction  15.2 ADO.NET Architecture  15.3 A Database Connection  15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters  15.5 Hands-On Tutorial: Displaying Data from Join of Tables  15.6 Hands-On Tutorial: Displaying Data Using Access Query  15.7 Hands-On Tutorial: Passing Data between Forms  15.8 DataSets  15.9 Inserts, Updates, and Deletes in a Windows Application  15.10 Hands-On Tutorial: Updating Changes to Multiple Tables  15.11 In-Class Assignment  15.12 Summary

9. 9 A Database Connection  Creating a database connection is like opening a unique session with the database –We can access contents of the database using the connection object –There are two ways to create a database connection in Visual Studio:  Using the Data Source Configuration wizard  Using the Server Explorer Window

10. 10 Creating the Project and Data Connection  How-to: Create a Connection Using the Server Explorer Window 1.Create a new Windows Application with the name, AdvanceDBConnectivity. 2.Select the View | Server Explorer option from the Main menu to open the Server Explorer Window. 3.Right-click the Data Connection node in the window and choose the Add Connection option. Adding a Connection in the Server Explorer Window

11. 11 Creating the Project and Data Connection (cont.) 4.If the Choose Data Source dialog box opens, select the Microsoft Access Database File option and click Continue. Otherwise, we should directly see the Add Connection dialog box. Select the University database. Test the connection and click OK. The Add Connection Dialog Box

12. 12 Creating the Project and Data Connection (cont.) 5.Collapse the Tables node and Views node to explore the list of tables and queries from the University database. Server Explorer Window for University Database

13. 13 Creating the Data Source 6.Choose the Data | Show Data Sources option from the Main menu. 7.In the Data Sources Window, click Add New Data Source to start the Data Source Configuration wizard. 8.Select the Database icon on the Choose a Data Source Type page, and then click Next. 9.On the Choose Your Data Connection page, accept the University database connection we have created in the previous step and click Next. Accepting Connection Created in the Server Explorer Window

14. 14 Creating the Data Source (cont.) 10.When enquired, copy the database to the current project folder. Click Next. 11.On the next page of the wizard save the connection with the default name UniversityConnectionString. Click Next. 12.Expand the Tables node on the Choose Your Database Objects page, and select all the tables except the college table and click Finish. The Data Sources Window now displays the UniversityDataSet tables. Selecting Tables for a Data Source Data Sources Window

15. 15 Properties of a Connection Object  There are several important properties related to Connection objects: –Name:  The name given to a Connection object –Connection String:  The string that stores the information required to connect to the database  A typical ConnectionString property resembles the following string: –Provider:  Shows the type of the database  Jet Engine for MS Access database –Data Source:  Stores the physical path of the database file

16. 16 Methods of a Connection Object  There are two primary methods available for Connection objects: –Open:  This method makes use of the information in the ConnectionString to locate the database and open a unique session to work with it –Close:  This method shuts the connection down.  Closing connections is essential because most databases support only a limited number of open connections  We use a TableAdapter to maintain the Connection object –Opens and closes the connection as per the applications need –Makes application development easier, faster, and less error-prone

17. 17 Overview  15.1 Introduction  15.2 ADO.NET Architecture  15.3 A Database Connection  15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters  15.5 Hands-On Tutorial: Displaying Data from Join of Tables  15.6 Hands-On Tutorial: Displaying Data Using Access Query  15.7 Hands-On Tutorial: Passing Data between Forms  15.8 DataSets  15.9 Inserts, Updates, and Deletes in a Windows Application  15.10 Hands-On Tutorial: Updating Changes to Multiple Tables  15.11 In-Class Assignment  15.12 Summary

18. 18 Create a DataGridView Control  This application will be based on the faculty table –The two parameters are the faculty’s department and salary, which are input by the user –We display the faculty members who belong to the user-specified department and whose salary is at least as much as specified by the user  How-to: Display Data on a Form with Multiple Parameters 1.In the Data Sources Window, locate and drag the faculty table onto Form1. This creates:  The data bound DataGridView control  A ToolStrip control  Related objects in the Component tray

19. 19 Open the DataSet Designer 2.Right-click TblFacultyTableAdapter from the Component tray and choose Edit Queries in DataSet Designer option to open the DataSet Designer tab. –Alternatively:  Double-click the DataSet (.xsd) file from the Solution Explorer Window  Click the Edit DataSet with Designer icon from the Data Sources Window Invoking the DataSet Designer to Edit Queries Opening the DataSet Designer

20. 20 Adding Parameter Queries 3.Select the TblFacultyTableAdapter in the DataSet Designer, right-click “Fill, GetData ()” text, and choose the Configure option. This should open the TableAdapter Configuration wizard. Review and Configure Existing Queries in a TableAdapter

21. 21 Adding Parameter Queries (cont.) –In the TableAdapter Configuration wizard, we have the Select query based on the faculty table.  We can modify the existing query by either editing the SQL statement or using the Query Builder dialog box. Edit Existing Query Using TableAdapter Configuration Wizard

22. 22 Adding Parameter Queries (cont.) 4.Select the TblFacultyTableAdapter in the DataSet Designer and right-click to choose the Add Query option to open the Query Configuration wizard. 4.On the first page of the wizard (Choose a Command Type), choose the Use SQL statements option and click Next. Adding a Query to a TableAdapter Choosing a Command Type

23. 23 Adding Parameter Queries (cont.) 6.On the next page (Choose a Query Type), choose the first option (SELECT which returns rows) and click Next. Choosing the Query Type in TableAdapter Query Configuration Wizard

24. 24 Adding Parameter Queries (cont.) 7.On the next page (Specify a SQL SELECT statement), create a new query by entering the SQL statement on this page. Writing a SQL Query in TableAdapter Query Configuration Wizard

25. 25 Adding Parameter Queries (cont.) 8.Finally, name the Fill a DataTable and Return a DataTable methods as shown in below and click Finish. –The faculty TableAdapter now resembles below with its additional methods. Choose and Name the Methods to be Added to the TableAdapter Faculty TableAdapter with Parameterized Query

26. 26 Add Existing Query 9.Right-click the TblFacultyTableAdapter from the Component tray and choose the Add Query option to open the Search Criteria Builder dialog box. 10.Choose the Existing query name option. Then, choose the FillByDeptSal method we created in the previous step from the drop-down list. 11.Click OK to create two TextBox controls for user input in the ToolStrip. Assigning a Query to a TableAdapter in the Search Criteria Builder Dialog Box

27. 27 Test the Application 12.Press Ctrl + F5 to run and test the application.  Enter values for the department and salary parameters through the TextBox controls on the ToolStrip and check if all the records satisfy the specified criteria. Running Application with Two Input Parameters

28. 28 Code Review  Note the code used to assign multiple parameters (lines 21-25). Code Review for the Multiple Parameter Query

29. 29 Overview  15.1 Introduction  15.2 ADO.NET Architecture  15.3 A Database Connection  15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters  15.5 Hands-On Tutorial: Displaying Data from Join of Tables  15.6 Hands-On Tutorial: Displaying Data Using Access Query  15.7 Hands-On Tutorial: Passing Data between Forms  15.8 DataSets  15.9 Inserts, Updates, and Deletes in a Windows Application  15.10 Hands-On Tutorial: Updating Changes to Multiple Tables  15.11 In-Class Assignment  15.12 Summary

30. 30 Add a New TableAdapter  How-to: Display Data on a Form from a Join of Multiple Tables 1.Add a new form, Form2, to the AdvanceDBConnectivity application. 2.Open the DataSet Designer. Right-click anywhere in the designer window and choose the Add | TableAdapter option to open the TableAdapter Configuration wizard. Adding a New TableAdapter to the Application

31. 31 Add a New TableAdapter (cont.) 3.On the Choose Your Data Connection page, accept the selected University database connection string. Click Next. 4.On the Choose a Command Type page, check Use SQL statements option (default) and click Next. Specifying Connection for a New TableAdapter

32. 32 Add a New TableAdapter (cont.) 5.On the Enter a SQL Statement page, click on the QueryBuilder button. In the Add Table dialog box that opens, select the student and transcript tables and click Add. Adding Query Tables in the Query Builder Dialog Box

33. 33 Add a New TableAdapter (cont.) 6.Note that the two selected tables appear in the table pane of the Query Builder dialog box. Click Close on the Add Table dialog box. Query Builder Dialog Box Showing the Query Design

34. 34 Add a New TableAdapter (cont.) 7.Select the fields to be displayed from the student and transcript tables (StudentID, DeptID, and Name from student table and Grade field from the transcript table).  Notice that the corresponding SQL Select query (performing the join of the two tables) is automatically built in the SQL pane as we select the fields. 8.Now add the DISTINCT keyword after the SELECT keyword in the SQL pane. 9.Add the query parameters (DeptID and Grade) in the WHERE clause.

35. 35 Add a New TableAdapter (cont.) 10.Click OK on the Query Builder dialog box. Click Next on the Table Adapter Configuration wizard, accept the default method names Fill and GetData, and click Finish. Newly Added TableAdapter in the DataSet Designer Newly Added DataTable in the Data Sources Window

36. 36 Create a DataGridView Control and Test 11.From the Data Sources Window, drag-and-drop the DataTable1 table on Form2 to create a DataGridView control. 12.Set Form2 as the start-up object. Press Ctrl + F5 to run the application. Test the application by entering different department IDs through the ToolStrip. Data from the Join of Two Tables

37. 37 Overview  15.1 Introduction  15.2 ADO.NET Architecture  15.3 A Database Connection  15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters  15.5 Hands-On Tutorial: Displaying Data from Join of Tables  15.6 Hands-On Tutorial: Displaying Data Using Access Query  15.7 Hands-On Tutorial: Passing Data between Forms  15.8 DataSets  15.9 Inserts, Updates, and Deletes in a Windows Application  15.10 Hands-On Tutorial: Updating Changes to Multiple Tables  15.11 In-Class Assignment  15.12 Summary

38. 38 Add Access Query  How-to: Display Data Using Existing MS Access Query 1.Add a Form3 to the AdvanceDBConnectivity application. 2.In the Data Sources Window, click the Configure DataSet with Wizard icon to open the Choose DataSet Editor dialog box. Using Data Sources Window to Invoke the Dataset Configuration Wizard

39. 39 Add Access Query (cont.) 3.Choose the Continue with wizard option to open the Data Source Configuration wizard. Invoking Data Sources Configuration Wizard

40. 40 Add Access Query (cont.) 4.On the last page of the wizard, Choose Your Database Objects, collapse the Views node and choose qryGPA, and click Finish. This adds the qryGPA as a DataTable in the Data Sources Window. Choosing the Query Access Query as a DataTable in the Data Sources Window

41. 41 Create a DataGridView and Test 5.From the Data Sources Window, drag-and-drop the qryGPA data table on Form3 to create a DataGridView control. 6.Set Form3 as the start-up object. Press Ctrl + F5 to run the application. Navigate through the student records and notice that the calculated GPA is displayed in column 5. Running Application with Student GPAs

42. 42 Overview  15.1 Introduction  15.2 ADO.NET Architecture  15.3 A Database Connection  15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters  15.5 Hands-On Tutorial: Displaying Data from Join of Tables  15.6 Hands-On Tutorial: Displaying Data Using Access Query  15.7 Hands-On Tutorial: Passing Data between Forms  15.8 DataSets  15.9 Inserts, Updates, and Deletes in a Windows Application  15.10 Hands-On Tutorial: Updating Changes to Multiple Tables  15.11 In-Class Assignment  15.12 Summary

43. 43 Passing Data Between Forms Application Flow: Passing Data between Two Windows Forms

44. 44 Create the First (Faculty) Form  How-to: Pass Data between Two Windows Forms 1.Add Form4 to the AdvanceDBConnectivity application. 2.Drag-and-drop the faculty table from the Data Sources Window on Form4.  This should create the faculty DataGridView and related objects in the Component tray.

45. 45 Create the Second (Course) Form 3.Add Form5 to the same application. 4.Switch to the DataSet Designer by double-clicking on UniversityDataSet.xsd. 5.Right-click in the designer window to add a new TableAdapter. 6.Follow the TableAdapter Configuration wizard as described in the previous hands-on tutorial. On the Enter a SQL Statement page of the wizard, click on the Query Builder button and add tblSection and tblCourse tables to the query design. Design the SQL statement shown below using the Query Builder dialog box. Course Information Query for the Course Form

46. 46 Create the Second (Course) Form (cont.) 7.Rename the Fill method as FillFaculty before finishing the configuration wizard. 8.Name the new table adapter as qryFacultyCoursesTableAdapter and the new data table as qryFacultyCourses. 9.Drag-and-drop the qryFacultyCourses data table from the Data Sources Window on Form5.  This should create the courses DataGridView and related objects in the Component tray.

47. 47 Write a Subroutine 10.In the Form5.vb file, write a new subroutine LoadCourses as shown below.  Takes in the FacultyID as an argument and passes it as a parameter to the FillFaculty method. Subroutine to Load Course Information for a Given FacultyID

48. 48 Write Code to Handle Events 11.In the faculty form, Form4.vb, write the code for DataGridView’s DoubleClick event. Select the TblFacultyDataGridView from the left drop-down list and its DoubleClick event from the right drop-down list at the top of the Code Window. Associate the code below with this event. DoubleClick Event of a DataGridView for the Faculty Form

49. 49 Test the Application 12.Set Form4 as the application’s start-up object. Press Ctrl + F5 to run the application. Test the application by double-clicking any faculty record from the DataGridView and viewing the related course data. Running Application Showing Related Information

50. 50 Overview  15.1 Introduction  15.2 ADO.NET Architecture  15.3 A Database Connection  15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters  15.5 Hands-On Tutorial: Displaying Data from Join of Tables  15.6 Hands-On Tutorial: Displaying Data Using Access Query  15.7 Hands-On Tutorial: Passing Data between Forms  15.8 DataSets  15.9 Inserts, Updates, and Deletes in a Windows Application  15.10 Hands-On Tutorial: Updating Changes to Multiple Tables  15.11 In-Class Assignment  15.12 Summary

51. 51 DataSets  A DataSet is an in-memory relational database –As relational databases have tables, DataSets also have DataTables –As database tables have rows and columns, dataset’s DataTables also have DataRows and DataColumns –As database tables are related to each other through relationships, DataTables are linked together through DataRelations object The Architecture of a DataSet Object

52. 52 How-to: Create a DataSet and Add a DataTable  Creating a DataSet: –We can add a DataSet to an application using the Data Source Configuration wizard.  Adding a DataTable: –We can add a DataTable to a DataSet using the Data Sources Configuration wizard.

53. 53 How-to: Add a DataRow to a DataTable  In order to add a new record into a DataTable: –First create a new DataRow (lines 6-8) –Assign values to the DataColumns (lines 11-13) –Add a new row to the Rows collection of a DataTable (line 16) Adding a DataRow to a DataTable

54. 54 How-to: Edit a DataRow in a DataTable  In order to edit an existing row in a DataTable, we should first locate the DataRow, and then update its one or more columns. –Locate the DataRow using the DataTable’s FindBy method or by utilizing the row index. Editing a DataRow in a DataTable Editing a DataRow in a DataTable Using a Row Index

55. 55 How-to: Delete a DataRow in a DataTable  We can make use of the Delete method of a DataRow to delete a row –Again, we must find the row before we can delete it. Deleting a DataRow in a DataTable Deleting a DataRow from a DataTable Using a Row Index

56. 56 How-to: Commit Changes in a DataSet  The changes to DataSet are like changes in a Word document. –We must save the changes to update the Dataset –Initially, we check if the DataSet has been changed (line 55) –Then use its AcceptChanges method to commit insertions, edits, and deletions (line 57) Committing the Changes in a DataSet

57. 57 How-to: Filter and Sort Data  We can filter data by using the Filter property of a BindingSource  We can sort data using the Sort property of the BindingSource on the column name which we want to sort –Sort property supports DESC and ASC sort ordering Filtering and Sorting Data Using the Properties of a BindingSource Object

58. 58 Overview  15.1 Introduction  15.2 ADO.NET Architecture  15.3 A Database Connection  15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters  15.5 Hands-On Tutorial: Displaying Data from Join of Tables  15.6 Hands-On Tutorial: Displaying Data Using Access Query  15.7 Hands-On Tutorial: Passing Data between Forms  15.8 DataSets  15.9 Inserts, Updates, and Deletes in a Windows Application  15.10 Hands-On Tutorial: Updating Changes to Multiple Tables  15.11 In-Class Assignment  15.12 Summary

59. 59 Data Flow from Windows Forms to a Database  It is vital for an application to enable users to insert new data and edit, update, or delete existing data and then propagate those changes to the database –Two-stage propagating process:  Commit changes to DataSet  Commit changes to Database Two-Stage Propagating Process

60. 60 Maintaining Information About Changes  As a user makes changes in data-bind controls, the DataSets are automatically updated with the changes. –The DataRow object keeps track of these changes and can be accessed using its properties.

61. 61 Retrieving Changed Rows  It is also important that we are able to retrieve the changes made by a user. –Easily review the changes made by a user and possibly validate those changes before committing them to a database. –Efficiently handle and work with only the changed portion of the DataSet rather than the entire DataSet.

62. 62 Committing Changes in the DataSet  We can commit changes in the DataSet at: –The DataRow level –The DataTable level –The DataSet level

63. 63 Build the Application  How-to: Update (Save) Changes to the Database 1.Add a form (Form6) to the AdvanceDBConnectivity application. 2.Drag-and-drop the student DataTable on the form from the Data Sources Window. 3.Double-click the Save button on the ToolStrip to open the Code Window.

64. 64 Build the Application and Test 4.Use the code below to complete the TblStudentBindingNavigatorSaveItem_Click event. 5.Set Form6 as the start-up object of the application. Press Ctrl + F5 to run the application. Test the application by changing values in the DataGridView and by saving the changes using the ToolStrip’s Save button. Saving Changes to the Database

65. 65 Build the Application  How-to: Insert and Delete Records in the Database 1.Add two command buttons named cmdInsert and cmdDelete to Form6, as shown below. Form6 with Command Buttons to Insert and Delete Records

66. 66 Build the Application (cont.) 2.Replace the Click event code of the cmdInsert button with the code shown.

67. 67 Build the Application (cont.) –Replace the Click event code of the cmdDelete button with the code shown.

68. 68 Test the Application 3.Ensure that Form6 is set as the start-up form and press Ctrl + F5 to run the application. 4.Click the Insert button and insert the record [99999999, “James Adams”]. 5.Now click the Delete button and delete the record inserted in previous step, by giving the StudentID = 99999999 as input. Adding a New Record to the Database MessageBox Showing the Record Deleted from the Database

69. 69 Overview  15.1 Introduction  15.2 ADO.NET Architecture  15.3 A Database Connection  15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters  15.5 Hands-On Tutorial: Displaying Data from Join of Tables  15.6 Hands-On Tutorial: Displaying Data Using Access Query  15.7 Hands-On Tutorial: Passing Data between Forms  15.8 DataSets  15.9 Inserts, Updates, and Deletes in a Windows Application  15.10 Hands-On Tutorial: Updating Changes to Multiple Tables  15.11 In-Class Assignment  15.12 Summary

70. 70 Build the Application  How-to: Update Changes to Multiple Tables in the Database 1.Drag the related transcript table (under the student node) from the Data Sources Window on Form6. 2.Add a command button named cmdSave to the form. 3.Replace the Click event of the Save button with code shown below. Update Code: Part 1

71. 71 Build the Application (cont.) 3.(cont.) Replace the Click event of the Save button with code shown below. Update Code: Part 2

72. 72 Build the Application (cont.) 3.(cont.) Replace the Click event of the Save button with code shown below. Update Code: Part 3

73. 73 Test the Application 4.Press Ctrl + F5 to run the application. 5.Change values in both the data grids and click Save. Update the record with the StudentID = 10100118 so that DeptID = “CISE” and Grade = 3.6. Running Application: Updating Multiple Tables in the Database

74. 74 Overview  15.1 Introduction  15.2 ADO.NET Architecture  15.3 A Database Connection  15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters  15.5 Hands-On Tutorial: Displaying Data from Join of Tables  15.6 Hands-On Tutorial: Displaying Data Using Access Query  15.7 Hands-On Tutorial: Passing Data between Forms  15.8 DataSets  15.9 Inserts, Updates, and Deletes in a Windows Application  15.10 Hands-On Tutorial: Updating Changes to Multiple Tables  15.11 In-Class Assignment  15.12 Summary

75. 75 In-Class Assignment  Build an application with two forms: –The first form should display the output of Query1:  “List all the courses from the University database, where the course belongs to College name and has name LIKE Course name.” –Show the Query 1 output on a DataGridView on Form1. –When a user double clicks any course entry in the DataGridView, we should open the second form which displays the output of the following query:  “List all the sections that belongs to the course selected on the first form and have capacity of at least 40 students.”

76. 76 Overview  15.1 Introduction  15.2 ADO.NET Architecture  15.3 A Database Connection  15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters  15.5 Hands-On Tutorial: Displaying Data from Join of Tables  15.6 Hands-On Tutorial: Displaying Data Using Access Query  15.7 Hands-On Tutorial: Passing Data between Forms  15.8 DataSets  15.9 Inserts, Updates, and Deletes in a Windows Application  15.10 Hands-On Tutorial: Updating Changes to Multiple Tables  15.11 In-Class Assignment  15.12 Summary

77. 77 Summary  ActiveX Data Objects (ADO).NET is the collection of objects that are designed to support data access and data manipulation  Database connectivity involves the following entities: –Database  Stores data on the hard drive (disk) –Connection  Connects to the database –DataAdapter  Hosts SQL queries and executes them against the database –DataSet  Stores data in main memory –Form  Displays data to the user

78. 78 Summary (cont.)  ADO.NET objects interact from database to Windows forms: 1.A Connection object opens a live connection to the database. 2.A DataAdapter object executes Select SQL queries against the database. 3.The DataAdapter object further fills a DataSet object with query results.  The DataSet stores the results in the main memory.  ADO.NET objects interact from Windows forms to database: 1.If a user edits the data in Windows controls, the updates are propagated to the DataSet object. 2.The DataAdapter object then propagates the updates from the DataSet object to the connected database by executing Update SQL statements.

79. 79 Summary (cont.)  Creating a database connection is like opening a unique session with the database. –Once opened, we can access contents of the database using the Connection object.  We considered some advanced topics in displaying data on Windows forms. –How to display data from a query with multiple parameters. –How to display data from a join of two or more tables. –How to make use of existing MS Access queries to display data on forms. –How to pass data between two Windows forms.

80. 80 Summary (cont.)  A DataSet is essentially an in-memory relational database. –A DataSet may contain one or more DataTables. –Each DataTable can have multiple DataRows and DataColumns. –DataSets act as a cache for a Windows application.  We considered topics like how to insert, update, and delete rows from the database with the two-stage updates strategy. –Finally, to conclude the chapter, we showed how to handle propagation of changes to the database for related or multiple tables.