chapter thirteen working with access databases and linq programming with microsoft visual basic 2010...

Chapter Thirteen

Working with Access Databases and LINQ

Programming with Microsoft Visual Basic 2010

5th Edition

Programming with Microsoft Visual Basic 2010, 5th Edition

Previewing Paradise Bookstore ApplicationOpen 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)

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Lesson A ObjectivesAfter studying Lesson A, you should be able to: Understand basic database terminologyConnect an application to a Microsoft Access

databaseBind table and field objects to controlsExplain the purpose of the DataSet,

BindingSource, TableAdapter, TableAdapterManager, and BindingNavigator objects

Customize a DataGridView ( 資料方格展示 ) controlHandle exceptions ( 異常 ) using the Try…Catch

statementPosition the record pointer in a dataset


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 fieldEach row in a table represents a record

FieldA single piece of information about a person,

place, or thing

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Database Terminology (cont’d.)

RecordA group of related fields that contain all the

necessary data about a specific person, place, or thing

Table: A group of related recordsEach record in a table pertains to the same topic

and contains the same type of informationPrimary key:

A field uniquely identifying a record Foreign key

A field that links a child record to a parent record

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example

example


Figure 13-4 Example of a 2-table relational database

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Connecting an Application to a Microsoft Access DatabaseMS Access 2007 database has a file

extension of .accdbSample database contains one table named

tblEmploy, containing employee informationMust create a database connection to access

dataData Source Configuration Wizard

Helps you connect an application to a databaseDataset

Temporary copy of the data you have requested from the database

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example


Figure 13-5 Data contained in the tblEmploy table

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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 fileClick 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

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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 window1.Choose type of database (data source)

Click New Connection button, and then select Microsoft Access Database File (OLE DB)

2.Choose file name of databaseClick 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, 5th Edition11


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 stringOn Choose Your Database Objects

screen, select tblEmployee table of the Employees.accdb database

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screen

screen



Figure 13-7 Message regarding copying the database file

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Figure 13-8 Objects selected in the Choose Your Database Objects screen

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Figure 13-9 Result of running the Data Source Configuration Wizard

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Previewing the Contents of a DatasetClick the form to make it the active windowClick 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

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screen


Figure 13-10 Data displayed in the Preview Data dialog box

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Binding the Objects in a Dataset Must bind one or more objects in the dataset

to controls in the interface to view dataset contents

BindingConnecting a dataset object to an interface

controlBound controls

Controls connected to dataset objects Types of controls used to bind dataset objects

Computer-created controlExisting control on the form

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explanation


Figure 13-11 Ways to bind an object in a dataset

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details


Having the Computer Create a Bound ControlWhen you drag a dataset object onto a form:

Computer creates control (its type is indicated by icon)

The dataset object is automatically bound to controlExample

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

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result

Data Sources window

example 1

example 2

實作練習在第 752 頁


Figure 13-12 Icons in the Data Sources window

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Figure 13-15 Result of dragging the table object to the form

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control name : TblEmployBindingNavigatorSaveItem


Figure 13-13 Result of clicking the tblEmploy object’s list arrow

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Figure 13-14 Result of clicking the Last_Name object’s list arrow

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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

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GUI

relationship among these objects


Figure 13-16 Illustration of the relationships among the database, the objects in the component tray, and the bound controls

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in hard disk

in memory

on GUI


The DataGridView ControlDataGridView control

Displays data in a row and column formatCell: Intersection of a row and columnDataGridView’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 sizedFill setting: Automatically adjusts the column

widths so that the display area of the control is filled

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screen


Figure 13-17 DataGridView control’s task list

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explanation

programmer

user


Figure 13-18 Purpose of each task in the DataGridView’s task list

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screen


Figure 13-19 Edit Columns dialog box

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CellStyle

dialog


Figure 13-20 Completed CellStyle Builder dialog box

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Figure 13-21 DataGridView control after setting some of its properties

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實作練習在•第 755~756 頁


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

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automatically entered code


Visual Basic Code (cont’d.)

Figure 13-22 Code automatically entered in the Code Editor window

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control & component

relationship among these objects


Handling Errors in the CodeException

Error that occurs while an application is running

Try…Catch statementUsed to intercept exceptions and handle

themTry code block

Contains the statements that might failCatch code block

Contains the code to handle the exceptions

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syntax


Figure 13-23 Syntax of the Try…Catch statement (continues)

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example


Figure 13-23examples of the Try…Catch statement


Figure 13-24 Completed Click event procedure for the Save Data button

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實作練習在•第 758~760 頁


Figure 13-25 Data displayed in the DataGridView control

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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 startsResult: database file appears in two different folders Changes to file in bin\Debug folder are overwritten

Copy if newer: Preserves run-time changesCopies over the file in bin\Debug only if it is not current

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Binding to an Existing ControlCan bind an object in a dataset to an existing

control on the form in two ways:Drag object from Data Sources window to controlSet one or more of the control’s properties in the

Properties windowProperties to set depend on the type of control

being bound:DataGridView: Set DataSource propertyListBox: Set DataSource and DisplayMember

properties Label or text box: Set DataBindings /Text

property

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實作練習•下載 Morgan Industries Soultion-Labels•在第 762~764 頁


Coding the Next Record and Previous Record ButtonsBindingSource object’s Position property

Stores an invisible record pointer Positions are integer values 0 First record is at position 0

BindingSource object’s Move methodsCan be used to move the record pointer in a

dataset to the first, last, next, or previous record in the dataset

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control & componentrelationship among

these objectsexamples

syntax


Figure 13-29 Syntax and examples of the BindingSource object’s Position property

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Figure 13-30 Syntax and examples of the BindingSource object’s Move methods

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Figure 13-31 Application’s code

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實作練習•在第 765~766 頁


Lesson A SummaryUse Data Source Configuration Wizard to

connect an application to a databaseUse the Preview Data command on the

Data menu to preview the data in a datasetBind 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

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Lesson A Summary (cont’d.)Use Dock property of DataGridView to

anchor it to the borders of formUse 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

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Lesson B ObjectivesAfter studying Lesson B, you should be able

to: Query a dataset using LINQCustomize a BindingNavigator controlUse the LINQ aggregate operators

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Creating a QueryQuery

Specifies the records to select from a datasetthe order in which to arrange the queried records

Language Integrated Query (LINQ)Used to create queries in Visual Basic 2010

Where clauseContains a condition to limit the records to be selected

Order By clauseUsed to arrange the records in ascending or descending order by one or more fields

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Figure 13-32 Basic LINQ syntax and examples

for selecting and arranging records in a dataset

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Figure 13-33 Syntax and an example of assigning a LINQ variable’s contents to a BindingSource object

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Figure 13-35 Employees whose last name begins with the letter S

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GUI of Morgan Industries Soultion-LINQ

下載 Morgan Industries Soultion-LINQ

實作練習


Figure 13-34 Code entered in the General Declarations section and btnFind Click event procedure

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Personalizing BindingNavigator Control

Can add additional items to a BindingNavigator control to personalize itButtonTextboxDrop-down button

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Figure 13-36 Manipulating the items on a BindingNavigator control

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Items Collection Editor


Figure 13-37 Items Collection Editor dialog box56


Figure 13-38 DropDownButton added to the TblEmployBindingNavigator control

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實作練習•下載 Morgan Industries Soultion-Aggregate•在第 777~779 頁


Using LINQ Aggregate Operators

Aggregate operatorReturns a single value from a group of values

LINQ provides several aggregate operatorsAverageCountMaxMinSum

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syntax & example


Figure 13-39 Syntax and examples of the LINQ aggregate operators

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Lesson B SummaryUse LINQ to select and arrange records in a

datasetYou can customize the BindingNavigator

control by adding additional items to itLINQ provides aggregate operators that

return a single value from a group of values

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Lesson C ObjectivesAfter studying Lesson C, you should be able

to: Prevent the user from adding and deleting

recordsRemove buttons from a BindingNavigator

controlAdd a label, text box, and button to a

BindingNavigator control

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Complete Paradise Bookstore Application

Requirements for Paradise Bookstore application Display records from the Books databaseAllow store manager to enter an author’s name

(or part of a name) to display books by that author

Database contains one table, tblBooksHas five fields and 11 records

User should not be allowed to add or delete recordsMust modify the BindingNavigatorControl to

remove the add and delete buttons

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data

GUI


Figure 13-42 tblBooks table in the Books database

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Figure 13-44 Completed TblBooksBindingNavigator control

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實作練習•下載 Paradise Bookstore Solution•建立使用者介面•在第 787~789 頁


Coding Paradise Bookstore Application

Go button’s Click event procedureDisplays only records whose Author field

starts with the characters entered in the text boxIf text box is empty, display all records

Use the LINQ LIKE operatorTotal Value button’s Click event procedure

Displays the total value of all books in the store

Use the LINQ aggregate function SUM

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GUI

example

example


Figure 13-45 Books written by authors whose name begins with s

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Coding the Paradise Bookstore Application (cont’d.)

Figure 13-46 Message box showing the total value of the inventory

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Figure 13-47 Click event procedures

for the btnGo and btnTotal controls

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實作練習•Buttons Go & Toal Value 的程式•在第 789~791 頁


Lesson C SummaryUse 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

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chapter thirteen working with access databases and linq programming with microsoft visual basic 2010...

Documents

microsoft visual basic

table relational database

database connection

accdbsample database

necessary data

file application

access databases

tblemploy table