CSC 330 Object-Oriented

Transcription

1 CSC 330 Object-Oriented Oriented Programming Using ADO.NET and C# CSC 330 Object-Oriented Design 1

2 Implementation CSC 330 Object-Oriented Design 2

3 Lecture Objectives Use database terminology correctly Create Windows and Web projects that display database data Display data in a DataGridView control Bind data to text boxes and labels Allow the user to select from a combo box or list box and display the corresponding record in data-bound controls Query an object using LINQ CSC 330 Object-Oriented Design 3

4 C# and Databases C# applications can display and update data from database files C# uses ADO.NET for database access ADO.NET is the next generation of database technology, based on Microsoft's previous version, ActiveX Data Objects (ADO) Information is stored and transferred in Extensible Markup Language (XML) ADO. NET allows access to database data in many formats This text uses Microsoft's SQL Server Express (SSE), which installs automatically with Visual Studio CSC 330 Object-Oriented Design 4

5 Database Terminology - 1 A database file (from SQL Server Express or Access) can hold multiple tables Table Can be viewed as a spreadsheet Row (record) Data for one item, person, or transaction Column (field) Stores an individual element of data, such as account number, name, address, etc. Primary key field Uniquely identifies each record CSC 330 Object-Oriented Design 5

6 Database Terminology - 2 Relational databases contain multiple tables and relationships between tables Relationships keep data compact and easy to maintain Whenever a database table is open, one record is considered the current record The current record changes as you move from one record to the next CSC 330 Object-Oriented Design 6

7 Database Terminology - 3 Database table example CSC 330 Object-Oriented Design 7

8 XML Data - 1 XML is an industry-standard format for storing and transferring data The XML needed for accessing databases is automatically generated in C# Data stored in XML is text, identified by tags similar to HTML tags Can be edited by any text editor program Tags in XML are not predefined as they are in HTML Tags can identify fields by name CSC 330 Object-Oriented Design 8

9 XML Data - 2 An XML data file is usually accompanied by a schema file Schema describes the fields, data types, and any constraints, such as required fields ADO.NET validates the data against the schema and checks for constraint violations Schema is also defined with XML tags and can be viewed or edited in a text editor An XML schema provides for strong data typing ADO.NET can treat the XML data as objects Allows IntelliSense to provide information to the programmer CSC 330 Object-Oriented Design 9

10 Using ADO.NET and C# - 1 In C# display data from a database on a Windows or Web Form Add controls to the form and bind data to the controls Labels or text boxes Specialized controls designed just for data, such as a DataGridView or a DataList Data handling and controls differ greatly for Windows and Web applications Both will be covered in this chapter CSC 330 Object-Oriented Design 10

11 Using ADO.NET and C# - 2 The DataGridView control is bound to a table in a dataset Data fields display automatically in the cells of the grid CSC 330 Object-Oriented Design 11

12 Data Access in Visual Studio - 1 The Data Sources window provides an easy way to create data-bound controls on a form Drag tables and fields from the window onto a form to create controls that are bound to the data Display the data in a grid or in individual fields, referred to as Details Drag a field from the Data Sources window and drop on an existing control, which automatically sets up data binding Adding data-bound controls to a form: Adds an.xsd file to the Solution Explorer window Adds BindingSource, TableAdapter, DataSet, and BindingNavigator objects to the component tray CSC 330 Object-Oriented Design 12

13 Data Access in Visual Studio - 2 Overview of database objects Binding source Establishes a link to the actual data a specific file and/or server Table adapter Handles retrieving and updating the data Generates SQL statements that are used to retrieve or update data Dataset Contains the actual data and may come from multiple binding sources and/or multiple table adapters Binding navigator A toolbar that provides for database navigation and updating CSC 330 Object-Oriented Design 13

14 Binding Sources Object establishes a link from a specific file or database to the program Use a wizard to automatically create BindingSource objects Add new BindingSource objects using the Data Sources window or the Data menu CSC 330 Object-Oriented Design 14

15 Table Adapters Does all the work of passing data back and forth between a data source (the binding source) and a program (the dataset) Data does not have to be from a database Data can be text file, object, or an array Transfers data from the source to the dataset (fills) or from the dataset back to the source (updates) via XML CSC 330 Object-Oriented Design 15

16 Datasets Temporary set of data stored in memory Datasets are disconnected, the copy of data in memory does not keep an active connection to the data source Dataset may contain multiple tables and relationships Any controls bound to the dataset will automatically fill with data CSC 330 Object-Oriented Design 16

17 Creating a Database Application - 1 Start a New Project Add a DataGridView control to the form to display the data Click the Smart Tag arrow Drop down the list for Choose Data Source Select Add Project Data Source which activates the Data Source Configuration Wizard Select Database CSC 330 Object-Oriented Design 17

18 Creating a Database Application - 2 Select New Connection Set up the connection for the binding source object In the Add Connection dialog box set the Data source and browse to the database file Open and test the connection Follow wizard prompts to add the database file to the project (makes the project portable) CSC 330 Object-Oriented Design 18

19 Creating a Database Application - 3 Run the Data Application Examine the Components Format the DataGridView Click on the DataGridView and click on the Smart Tag arrow Select Edit Columns Add, remove and reorder columns Set HeaderText, ToolTip Text and other properties Run the Application CSC 330 Object-Oriented Design 19

20 The Grid s Smart Tag Use the smart tag to: Edit properties of grid columns Add and edit columns Dock the grid in its parent container (the form) Allows grid to fill form, even if form is resized CSC 330 Object-Oriented Design 20

21 The Database Schema File An.xsd file is added to the Solution Explorer for each new data source added to a project Contains the XML schema definition, the description and properties of the data Keys Names of tables and fields, primary keys, and the table relationships At the bottom of the schema appears the TableAdapter for the table Handles the Fill and GetData methods for the table TableAdapter CSC 330 Object-Oriented Design 21

22 Binding Individual Data Fields - 1 Table fields from the dataset can be bound to many types of controls i.e. labels, text boxes, combo boxes, check boxes Controls that are connected to fields are referred to as bound controls or data-bound controls Create bound controls using the automatic binding features of the Data Sources window Drag the table to the form Creates individual text box controls for each field of data and a navigation control CSC 330 Object-Oriented Design 22

23 Binding Individual Data Fields - 2 Each text box is bound to one field from the table As the user clicks the navigation buttons, all controls change to display the data for the next record Navigation buttons CSC 330 Object-Oriented Design 23

24 The Data Sources Window Select Show Data Sources from Data menu to display Add a new data source Click on the table name and select Details from the drop-down list The table's icon changes from a grid to indicate details CSC 330 Object-Oriented Design 24

25 Selecting Records from a List Instead of providing navigation from one record to the next, allow the user to select a record from a drop-down list The rest of the fields will fill with data elements for the selected record Select a last name from the drop-down list CSC 330 Object-Oriented Design 25

26 In the Data Sources window click on the LastName field Converting to Combo Box Selection - 1 Select ComboBox from the list Drag the LastName field from the Data Sources window to the form Creates a Combo Box control and label CSC 330 Object-Oriented Design 26

27 Converting to Combo Box Selection - 2 Use the combo box smart tag to set up data binding Select Use data bound items to display the binding choices Drop down list to select the binding source Select the field to display in the list CSC 330 Object-Oriented Design 27

28 Selecting Fields from the Table When you create the Data Source Choose Add New Data Source option from the Data menu or the Data Sources window In the Choose Your Database Objects section of the Configuration wizard Expand the Tables node and place a check mark on just the fields needed After the Data Source is created Select the dataset in the Data Sources window Click the Configure DataSet Wizard button Follow same steps as above CSC 330 Object-Oriented Design 28

29 Sorting the List Data - 1 Cannot sort a data-bound list using the Sorted property of the control Sort the data in the Select query Double-click the dataset s schema file in the Solution Explorer (.xsd file) In the displayed schema, click on Fill,GetData() Click on the Property button ( ) for the CommandText property CSC 330 Object-Oriented Design 29

30 Sorting the List Data - 2 Schema file View the Select query in the pop-up data tip Click on the Fill command SELECT query in Command- Text property CSC 330 Object-Oriented Design 30

31 Sorting the List Data - 3 Modify the SQL SELECT command Drop down the Sort Type list and choose Ascending or Descending (or type directly into the SELECT statement) SQL statement changes to include an ORDER BY clause CSC 330 Object-Oriented Design 31

32 Choosing the Control Type for Fields Dragging a Details view to a form displays text boxes by default for text fields Click a field name and choose a control type in the Data Sources window Choose the control type for all controls and then drag the table to the form to create the Details view CSC 330 Object-Oriented Design 32

33 LINQ Language-Integrated Query (LINQ) General-purpose query language that can ask a question of any data Object, database or XML Data source can be a database or any collection such as an array or list box collection LINQ to SQL component Converts database items to objects LINQ to XML component Converts XML document collections to objects CSC 330 Object-Oriented Design 33

34 Setting up a Query - 1 Standard operators, regardless of data source Primary operators in a query from, in, where and select LINQ Query General Form variablename = from itemname in objectname select fieldname list of Fields items variablename does not need a data type assigned The compiler can assign a type in a process called type inference Allows LINQ operators order by and where to be used on unspecified data types CSC 330 Object-Oriented Design 34

35 Setting up a Query - 2 The LINQ Query Example var belowminimumquery = from an Item in amountdecimal where an Item < 100m select an Item; amountdecimal is an array, anitem is a single element not declared elsewhere Query is similar to a foreach Steps through the array, assigns each element to anitem and performs a comparison CSC 330 Object-Oriented Design 35

36 LINQ to SQL - 1 A LINQ query can be applied to a relational database Add a LINQ to SQL Classes template to a database project Creates a strongly typed DataContext class A new design surface with two panes appears in the Document window Drag database tables from the Server Explorer to the design surface CSC 330 Object-Oriented Design 36

37 LINQ to SQL - 2 Tables added to the left pane are referred to as entities Right pane holds optional stored procedures or methods Refer to the DataContext when writing the code Once the DataContext class is created, create a DataContext object in code Query the database using the LINQ operators CSC 330 Object-Oriented Design 37

38 LINQ to SQL - 3 CSC 330 Object-Oriented Design 38