Chapter Thirteen Working with Access Databases and LINQ Programming with Microsoft Visual Basic th Edition

Programming with Microsoft Visual Basic 2010, 5 th Edition Previewing Paradise Bookstore Application Open the Paradise.exe file Application displays records in the Books database (data details) Allows store manager entering author’s name (or part of a name) Displays only books written by the author (data searching) Displays the total value of books in the store (data summary) 2

Programming with Microsoft Visual Basic 2010, 5 th Edition Lesson A Objectives After studying Lesson A, you should be able to: Understand basic database terminology Connect an application to a Microsoft Access database Bind table and field objects to controls Explain the purpose of the DataSet, BindingSource, TableAdapter, TableAdapterManager, and BindingNavigator objects Customize a DataGridView ( 資料方格展示 ) control Handle exceptions ( 異常 ) using the Try…Catch statement Position the record pointer in a dataset

Programming with Microsoft Visual Basic 2010, 5 th Edition Database Terminology Database in computer An electronic file containing an organized collection of related information Relational database A database that stores information in tables composed of rows and columns Each column in a table represents a field Each row in a table represents a record Field A single piece of information about a person, place, or thing 4

Programming with Microsoft Visual Basic 2010, 5 th Edition Database Terminology (cont’d.) Record A group of related fields that contain all the necessary data about a specific person, place, or thing Table: A group of related records Each record in a table pertains to the same topic and contains the same type of information Primary key: A field uniquely identifying a record Foreign key A field that links a child record to a parent record 5 example

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure 13-4 Example of a 2-table relational database 6

Programming with Microsoft Visual Basic 2010, 5 th Edition Connecting an Application to a Microsoft Access Database MS Access 2007 database has a file extension of.accdb Sample database contains one table named tblEmploy, containing employee information Must create a database connection to access data Data Source Configuration Wizard Helps you connect an application to a database Dataset Temporary copy of the data you have requested from the database 7 example

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure 13-5 Data contained in the tblEmploy table 8

Programming with Microsoft Visual Basic 2010, 5 th Edition Connecting an Application to a Microsoft Access Database (cont’d.) Open the Solution Explorer window and auto-hide the Properties window Open the Morgan Industries Solution file Click the View menu and then click Server Explorer (Visual Studio) or Database Explorer (Visual Basic Express) 實作練習 : 需下載 Chap13 的 Morgan Industries Solution-DataGridView Access Databases\Employees.accdb 9

Programming with Microsoft Visual Basic 2010, 5 th Edition Connecting an Application to a Microsoft Access Database (cont’d.) Click the Data on the menu bar and then click Show Data Sources to open Data Sources window Click Add New Data Source button, and then select Database to open Add Connection window 1. Choose type of database (data source) Click New Connection button, and then select Microsoft Access Database File (OLE DB) 2. Choose file name of database Click Browse, navigate to database file, and then click Open 3. Click Test Connection button, and if successful, click Next 實作練習 在第 745~748 頁 10 screen

Programming with Microsoft Visual Basic 2010, 5 th Edition 11

Programming with Microsoft Visual Basic 2010, 5 th Edition Connecting an Application to a Microsoft Access Database (cont’d.) Click Yes to include the database file in the current project Click Yes to save connection string On Choose Your Database Objects screen, select tblEmployee table of the Employees.accdb database 12 screen

Programming with Microsoft Visual Basic 2010, 5 th Edition Connecting an Application to a Microsoft Access Database (cont’d.) Figure 13-7 Message regarding copying the database file 13

Programming with Microsoft Visual Basic 2010, 5 th Edition Connecting an Application to a Microsoft Access Database (cont’d.) Figure 13-8 Objects selected in the Choose Your Database Objects screen 14

Programming with Microsoft Visual Basic 2010, 5 th Edition Connecting an Application to a Microsoft Access Database (cont’d.) Figure 13-9 Result of running the Data Source Configuration Wizard 15

Programming with Microsoft Visual Basic 2010, 5 th Edition Previewing the Contents of a Dataset Click the form to make it the active window Click Data on the menu bar and then click Preview Data to open Preview Data dialog box Select the object to preview and then click Preview After previewing the data, click Close button 實作練習 在第 748~749 頁 16 screen

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Data displayed in the Preview Data dialog box 17

Programming with Microsoft Visual Basic 2010, 5 th Edition Binding the Objects in a Dataset Must bind one or more objects in the dataset to controls in the interface to view dataset contents Binding Connecting a dataset object to an interface control Bound controls Controls connected to dataset objects Types of controls used to bind dataset objects Computer-created control Existing control on the form 18 explanation

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Ways to bind an object in a dataset 19 details

Programming with Microsoft Visual Basic 2010, 5 th Edition Having the Computer Create a Bound Control When you drag a dataset object onto a form: Computer creates control (its type is indicated by icon) The dataset object is automatically bound to control Example Drag tblEmployee table object from Data Sources window to the form DataGridView control is created to display tabular data, with rows representing records, columns representing fields Use list arrow to change the type of control linked to the object 20 result Data Sources window example 1 example 2 實作練習 在 第 752 頁

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Icons in the Data Sources window 21

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Result of dragging the table object to the form 22 control name : TblEmployBindingNavigatorSaveItem

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Result of clicking the tblEmploy object’s list arrow 23

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Result of clicking the Last_Name object’s list arrow 24

Programming with Microsoft Visual Basic 2010, 5 th Edition Having the Computer Create a Bound Control (cont’d.) In addition to a control, the computer adds: BindingNavigator control: To move from one record to the next in the dataset TableAdapter object: Connects the database to the DataSet object; responsible for retrieving data and storing it in the DataSet TableAdapterManager object: Handles saving data to multiple tables in the DataSet BindingSource object: Connects the DataSet to the bound controls 25 GUI relationship among these objects

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Illustration of the relationships among the database, the objects in the component tray, and the bound controls 26 in hard disk in memory on GUI

Programming with Microsoft Visual Basic 2010, 5 th Edition The DataGridView Control DataGridView control Displays data in a row and column format Cell: Intersection of a row and column DataGridView’s task list allows you to add, reorder, and remove columns and set properties of bound columns AutoSizeColumnsMode: Has seven settings that control how the column widths are sized Fill setting: Automatically adjusts the column widths so that the display area of the control is filled 27 screen

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure DataGridView control’s task list 28 explanation programmer user

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Purpose of each task in the DataGridView’s task list 29 screen

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Edit Columns dialog box 30 CellStyle dialog

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Completed CellStyle Builder dialog box 31

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure DataGridView control after setting some of its properties 32 實作練習 在 第 755~756 頁

Programming with Microsoft Visual Basic 2010, 5 th Edition Database Programming in VB When a table or field object is dragged onto a form, the computer also enters code in the Code Editor window Code in the form’s Load event uses the TableAdapter object to retrieve data BindingNavigator’s save event is also coded 33 automatically entered code

Programming with Microsoft Visual Basic 2010, 5 th Edition Visual Basic Code (cont’d.) Figure Code automatically entered in the Code Editor window 34 control & component relationship among these objects

Programming with Microsoft Visual Basic 2010, 5 th Edition Handling Errors in the Code Exception Error that occurs while an application is running Try…Catch statement Used to intercept exceptions and handle them Try code block Contains the statements that might fail Catch code block Contains the code to handle the exceptions 35 syntax

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Syntax of the Try…Catch statement (continues) 36 example

Programming with Microsoft Visual Basic 2010, 5 th Edition 37 Figure examples of the Try…Catch statement

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Completed Click event procedure for the Save Data button 38 實作練習 在 第 758~760 頁

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Data displayed in the DataGridView control 39

Programming with Microsoft Visual Basic 2010, 5 th Edition Copy to Output Directory Property Copy to Output Directory property: Determines the way Visual Basic saves changes to local file Copy always (default setting): Database file is copied to project’s bin\Debug folder each time the application starts Result: database file appears in two different folders Changes to file in bin\Debug folder are overwritten Copy if newer: Preserves run-time changes Copies over the file in bin\Debug only if it is not current 40

Programming with Microsoft Visual Basic 2010, 5 th Edition Binding to an Existing Control Can bind an object in a dataset to an existing control on the form in two ways: Drag object from Data Sources window to control Set one or more of the control’s properties in the Properties window Properties to set depend on the type of control being bound: DataGridView: Set DataSource property ListBox: Set DataSource and DisplayMember properties Label or text box: Set DataBindings /Text property 41 實作練習 下載 Morgan Industries Soultion-Labels 在第 762~764 頁

Programming with Microsoft Visual Basic 2010, 5 th Edition Coding the Next Record and Previous Record Buttons BindingSource object’s Position property Stores an invisible record pointer Positions are integer values  0 First record is at position 0 BindingSource object’s Move methods Can be used to move the record pointer in a dataset to the first, last, next, or previous record in the dataset 42 control & component relationship among these objects examples syntax

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Syntax and examples of the BindingSource object’s Position property 43

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Syntax and examples of the BindingSource object’s Move methods 44

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Application’s code 45 實作練習 在第 765~766 頁

Programming with Microsoft Visual Basic 2010, 5 th Edition Lesson A Summary Use Data Source Configuration Wizard to connect an application to a database Use the Preview Data command on the Data menu to preview the data in a dataset Bind an object in a dataset by dragging it to the form and letting the computer create a control or by dragging it onto an existing control Use the Fill setting of the DataGridView’s AutoSizeColumnsMode property to have columns fill the display area 46

Programming with Microsoft Visual Basic 2010, 5 th Edition Lesson A Summary (cont’d.) Use Dock property of DataGridView to anchor it to the borders of form Use the Try…Catch statement to handle exceptions (errors) occurring during run time Use BindingSource object’s Position property or its Move methods to move record pointer while the application is running 47

Programming with Microsoft Visual Basic 2010, 5 th Edition Lesson B Objectives After studying Lesson B, you should be able to: Query a dataset using LINQ Customize a BindingNavigator control Use the LINQ aggregate operators 48

Programming with Microsoft Visual Basic 2010, 5 th Edition Creating a Query Query Specifies the records to select from a dataset the order in which to arrange the queried records Language Integrated Query (LINQ) Used to create queries in Visual Basic 2010 Where clause Contains a condition to limit the records to be selected Order By clause Used to arrange the records in ascending or descending order by one or more fields 49

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Basic LINQ syntax and examples for selecting and arranging records in a dataset 50

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Syntax and an example of assigning a LINQ variable’s contents to a BindingSource object 51

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Employees whose last name begins with the letter S 52 GUI of Morgan Industries Soultion-LINQ 下載 Morgan Industries Soultion-LINQ 實作練習

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Code entered in the General Declarations section and btnFind Click event procedure 53 實作練習 在第 775~777 頁

Programming with Microsoft Visual Basic 2010, 5 th Edition Personalizing BindingNavigator Control Can add additional items to a BindingNavigator control to personalize it Button Textbox Drop-down button 54

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Manipulating the items on a BindingNavigator control 55 Items Collection Editor

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Items Collection Editor dialog box 56

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure DropDownButton added to the TblEmployBindingNavigator control 57 實作練習 下載 Morgan Industries Soultion-Aggregate 在第 777~779 頁

Programming with Microsoft Visual Basic 2010, 5 th Edition Using LINQ Aggregate Operators Aggregate operator Returns a single value from a group of values LINQ provides several aggregate operators Average Count Max Min Sum 58 syntax & example

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Syntax and examples of the LINQ aggregate operators 59 實作練習 在第 780~782 頁

Programming with Microsoft Visual Basic 2010, 5 th Edition Lesson B Summary Use LINQ to select and arrange records in a dataset You can customize the BindingNavigator control by adding additional items to it LINQ provides aggregate operators that return a single value from a group of values 60

Programming with Microsoft Visual Basic 2010, 5 th Edition Lesson C Objectives After studying Lesson C, you should be able to: Prevent the user from adding and deleting records Remove buttons from a BindingNavigator control Add a label, text box, and button to a BindingNavigator control 61

Programming with Microsoft Visual Basic 2010, 5 th Edition Complete Paradise Bookstore Application Requirements for Paradise Bookstore application Display records from the Books database Allow store manager to enter an author’s name (or part of a name) to display books by that author Database contains one table, tblBooks Has five fields and 11 records User should not be allowed to add or delete records Must modify the BindingNavigatorControl to remove the add and delete buttons 62 data GUI

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure tblBooks table in the Books database 63

Programming with Microsoft Visual Basic 2010, 5 th Edition 64 Figure Completed TblBooksBindingNavigator control 64 實作練習 下載 Paradise Bookstore Solution 建立使用者介面 在第 787~789 頁

Programming with Microsoft Visual Basic 2010, 5 th Edition Coding Paradise Bookstore Application Go button’s Click event procedure Displays only records whose Author field starts with the characters entered in the text box If text box is empty, display all records Use the LINQ LIKE operator Total Value button’s Click event procedure Displays the total value of all books in the store Use the LINQ aggregate function SUM 65 GUI example

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Books written by authors whose name begins with s 66

Programming with Microsoft Visual Basic 2010, 5 th Edition Coding the Paradise Bookstore Application (cont’d.) Figure Message box showing the total value of the inventory 67

Programming with Microsoft Visual Basic 2010, 5 th Edition Figure Click event procedures for the btnGo and btnTotal controls 68 實作練習 Buttons Go & Toal Value 的程式 在第 789~791 頁

Programming with Microsoft Visual Basic 2010, 5 th Edition Lesson C Summary Use the DataGridView control’s task box to prevent the user from adding or deleting records in the control Remove items from the BindingNavigator control to prevent the user from performing some actions Can customize the BindingNavigator control by adding a label, text box, or button to it 69