Chapter 10. Database Applications The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill

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1 Chapter 10 Database Applications McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved.

2 Chapter 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 10-2

3 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 10-3

4 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 10-4

5 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 10-5

6 Database Terminology - 3 Database table example McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 10-6

7 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 10-7

8 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 10-8

9 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 10-9

10 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

11 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

12 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

13 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

14 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

15 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

16 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

17 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) McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

18 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

19 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

20 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

21 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

22 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

23 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

24 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

25 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

26 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

27 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

28 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

29 Sorting the List Data - 2 Schema file View the Select query in the pop-up data tip SELECT query in Command- Text property Click on the Fill command McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

30 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

31 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

32 Selecting Records Using Web Forms Web controls are considerably different from their Windows counterparts Web-based database applications have additional security issues Web database applications operate differently than Windows applications due to the nature of Web pages in a client/server environment Web pages are stateless each time a page displays it is a new fresh page Each time the user makes a selection from a list a postback occurs and the Web page redisplays with only the selected data McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

33 Security in Web Database Applications Security is much tighter for Web database applications than for Windows applications Require user authentication and set permission levels, if setting up a Web application that displays or allows modification to data Visual Studio integrates security features, which are generally strict by default McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

34 Creating the Web Selection Application - 1 Web version of the selection program must have two data sources Drop-down list has a separate data source from the one used for the individual fields Begin a new Web site Copy the database file into the project s App_Data folder McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

35 Creating the Web Selection Application - 2 Set up the drop-down list Add a DropDownList control In the smart tag select Choose Data Source In the wizard, drop down the list for Select a data source and select New data source Select Database Click on the New Connection button In the Add Connection dialog box, browse to the database file Select the data fields for the dataset for the dropdown list on the Configure the Select Statement page McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

36 Creating the Web Selection Application - 3 Click on the ORDER BY button Select LastName to sort by On the Choose a Data Source page, LastName should be selected for both the data to display and the value of the field Select Enable AutoPostBack in the smart tag for the drop-down list control An important step necessary to select and display the data for the selected customer McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

37 Creating the Web Selection Application - 4 Select the fields to include in the dataset Click the ORDER BY button to define a sort McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

38 Creating the Web Selection Application - 5 Set up the additional fields Add a DetailsView control to the Web page In the smart tag, select New data source from the Choose a Data Source list Select Database and select the connection for the database file that is already created Configure the Select Statement Click on the box for all columns (*) Click the WHERE button In the Add WHERE Clause dialog box set up the parameter used to select the correct data for the fields Save all McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

39 Creating the Web Selection Application - 6 Run the Application Press Ctrl + F5 to test the application Make selections from the list Data fields should change to match selection McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

40 Make the Project Portable Open the Web.config file from the Solution Explorer Scroll to find the entry for the connection string Replace the path (not the file-name) with DataDirectory Close the project, copy the complete folder to move it to another location McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

41 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

42 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

43 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

44 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

45 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 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved

46 LINQ to SQL - 3 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved