CST141 ASP.NET Database Page 1

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1 CST141 ASP.NET Database Page ASP.NET Database CST242 Database A database (the data) A computer filing system I.e. Payroll, personnel, order entry, billing, accounts receivable and payable, contact list, etc. A database management system (DBMS) (the software) Program that manipulates the database A DBMS may have a GUI front end, but its database engine physically processes the data Database Processing Maintenance Keeping the database up-to-date (current) Adding, modifying and deleting records Retrieval allows access of meaningful information On-line (on the monitor/screen) Printed reports Database Terminology Database A collection of data tables and relationships Table Individual categories of data entities Record All of the data for one person or entity Called a row in relational DB terminology Field One element of data within a record Called a column in relational DB terminology The Primary Key Field or concatenation (combination) of fields which uniquely identify records in the table Most efficient tool for searching for specific records The primary key also is an index which controls the default sort order for the table Structured Query Language SQL (pronounced see -quel) A relational database language developed by IBM in mid-1970's Represents any data as one or more tables Non-procedural language...

2 CST141 ASP.NET Database Page 2 Lets the DBMS engine determine how the operation will be executed SQL commands can be embedded into procedural language programs like Java Data Retrieval in SQL Reporting in both printed and on-line formats Basic format: SELECT columnlist FROM table(s) WHERE condition SELECT clause limits columns returned (required) FROM clause names table from which data is extracted (required) WHERE clause limits rows returned (optional) Basic SELECT statement SELECT * FROM tablename The * is a wildcard that specifies all columns All rows also will be returned since there is no WHERE clause SELECT * FROM Book SELECT with column list A comma-delimited list of column names (fieldnames) that limits which columns are returned in a query SELECT columnname1[, columnname2 ] FROM tablename SELECT BookCode, Title, Price FROM Book The WHERE Clause (Page 1) Based on the truth condition of a relation condition (like in an if statement) that limits rows returned At least one factor in the WHERE condition will be a column name SELECT columnname1[, columnname2 ] FROM tablename(s) WHERE relation_condition The WHERE Clause (Page 2) Examples: SELECT Title, Type, Price

3 CST141 ASP.NET Database Page 3 FROM Book WHERE Type = "MYS" SELECT Title, PublisherCode FROM Book WHERE Not Paperback 14 The ORDER BY Clause (Page 1) Sorts the rows in the returned table sorting on the column or columns named in the ORDER BY clause SELECT columnname1[, columnname2 ] FROM tablename(s) ORDER BY columnname1[, columnname2 ] The ORDER BY Clause (Page 2) SELECT BookCode, Title, Price FROM Book ORDER BY Title To sort on major and minor sort fields: SELECT PublisherCode, Title FROM Book ORDER BY PublisherCode, Title Relationships (Linking) In databases with more than one table, there is a link on a common field This link (and the relational rules that apply to it) must be enforced By the DBMS as well as by Try Catch processing in the application Referential integrity is the rule which states that a common field in one table must match primary key in the other, or be null (blank) The Foreign Key The field that links a table in a relational database to the primary key in another table There may be multiple instances of a single value of the foreign key; however The foreign key must match one of the values of the primary key in the table to which it links, or by null (blank) SELECT with Join (Page 1) A join operation links related fields from more than one table SELECT columnname1[, columnname2 ] FROM tablename1 INNER JOIN tablename2 ON primarykey = foreignkey

4 CST141 ASP.NET Database Page 4 The datatype and field size of the primarykey and foreignkey fields must be the same SELECT with Join (Page 2) SELECT BookCode, Title, Name FROM Book INNER JOIN Publisher ON Book.PublisherCode = Publisher.PublisherCode Column names that exist in more than one table must be prefixed by the table name, i.e. Book.PublisherCode and Publisher.PublisherCode SELECT with Join and ORDER BY and/or WHERE WHERE and ORDER BY clauses may be combined into the same SQL statement SELECT BookCode, Title, Name FROM Book INNER JOIN Publisher ON Book.PublisherCode = Publisher.PublisherCode ORDER BY Name, Title WHERE Type = "MYS" An ASP.NET Web Site Project In Visual Studio a Web Site is a repository (folder/storage location) that contains files and additional folders that make up the project Creating a New Web Site Project (Page 1) To create a new ASP.NET project: 1. Select the File command from the menu bar 2. Click New from the File menu 3. Click Project from the New submenu; or Creating a New Web Site Project (Page 2) Alternately to create the new project: 1. Select the down arrow point ( ) on the New Project button from the Standard toolbar 2. Click New Project from the New Project submenu Creating a New Web Site Project (Page 3) Then in the New Project dialog window: 1. Make sure to verify that Visual C# is selected in the Installed Templates pane 2. Select ASP.NET Web Application (or ASP.NET Empty Web Application our preference in CST242) template 3. Give the Web Site a Name: 4. Make sure Create directory for solution checkbox stays checked

5 CST141 ASP.NET Database Page Creating a New Web Site Project (Page 4) In the New Web Site dialog window (con.): 4. Enter the project folder Location and name Click the <Browse > button to make it easier to select the folder location 5. Click the <OK> button In the New ASP.NET Project dialog window, from Select a template: select option Empty and click the <OK> button (make no other changes) In the Configure Microsoft Azure Web App dialog window click the <Cancel> button An ASP.NET Web Site (Page 1) Types of files in a website: ASP.NET web forms dynamic (interactive) web forms with two files: (1) the.aspx file which is the web page; and (2) the.aspx.cs file that contains the Visual C# code that runs on the server Image files for the website Configuration files web.config is a file that provides information for the server Static HTML web pages HTML code only; no ASP.NET Server Web controls An ASP.NET Web Site (Page 2) Types of files in a web site (con.): Style sheet files additional information that tells the browser how to format HTML elements; useful for creating consistent style on a Web page, or all the Web pages on a website Script files source code that runs on the client machine in the browser, e.g. JavaScript or VbScript Database files Web Forms in ASP.NET (Page 1) The Web Form consists of two components: The HTML template (.aspx extension) The actual web page that contains the design layout, content and controls A collection of code in a procedure language such as C# that commonly is located behind the Web Form ( aspx.cs extension) The code behind the page Web Forms in ASP.NET (Page 2) The ASP.NET Form Web control handles most of the HTML detail processing for the developer The input controls are generated using ASP.NET web controls, i.e. ASP:TextBox and ASP:Label The ASP:Button Web control is rendered by ASP.NET as a submit button The form is submitted when the button is clicked Web Forms in ASP.NET (Page 3)

6 CST141 ASP.NET Database Page 6 The format of the Form web control which wraps around the input elements is: <form id="formid" runat="server"> </form> This block is inserted automatically into every new ASP.NET web document Web Forms in ASP.NET (Page 4) When the Button control is clicked, the Web form is rendered as a postback <form> element (a POST method) which causes the web form to be reloaded Code (Visual C#) that should execute when the form is submitted is assigned to the Click event of the Button Additional hidden <input> elements are generated which provide information to ASP.NET Adding an Existing Item Existing items might include ASP.NET Web Forms, HTML pages, databases, image files, etc. Start by being certain folder that item is to be inserted into is selected in Solution Explorer 1. Select Project from the menu bar 2. Select Add Existing Item from the Website menu 3. Browse to Look in: folder 4. Select Files of type: from drop-down list 5. Select files and click <Add> button; the item(s) is/are added to specified folder in Solution Explorer Adding a New Item (Page 1) To add a new item/document to an ASP.NET project: 1. Select Project from the menu bar 2. Click Add New Item from the Website menu Or find Add New Item by right-clicking the website folder name in the Solution Explorer window Adding a New Item (Page 2) In the Add New Item dialog window: 1. Make sure to verify that Web is selected under Visual C# in the Installed pane 2. Select the document type an ASP.NET document page is a Web Form 3. Type filename (appropriate extension will be added) 4. Click <Add> button the new item is added to the Solution Explorer window The Solution Explorer Window Window on the upper right of IDE that lists the project files and resources (images, databases, etc.) Save the Web Form

7 CST141 ASP.NET Database Page 7 To save current document, click the <Save> button on the Standard toolbar It should not be necessary to name it in the Save As dialog window since it was given a name when it initially was created Open a Web Site (Page 1) To open an existing ASP.NET project: 1. Select the File command from the menu bar 2. Click Open from the File menu 3. Click Project from the Open submenu Open a Web Site (Page 2) In the Open Web Site dialog window: 1. Select the folder name that contains the Solution file (the main top folder) 2. Select the filename with the.sln extension 3. Click the <Open> button HTML (and ASP.NET) Tags Formatting codes that instruct the browser how to display page elements Tags are enclosed in angle brackets (< >) Most tags are two-sided First tag tells browser to turn on feature Second tag instructs browser to turn it off E.g. <b> begins boldface, </b> turns it off Sections of a Web Document Web pages in HTML usually are divided into two main sections head: defines the title of the page, information about the page to help search engines find it, style sheets, etc. body: specifies the content (visual elements) of the Web page HTML Basic Page Outline <html> <head> identifying elements </head> <body> visual content elements </body> </html> 44 <html> Encloses the entire HTML file

8 CST141 ASP.NET Database Page 8 Identifies the file to browser software as one containing HTML code, e.g. Microsoft Internet Explorer Foxfire Closing tag is </html> <head> Encloses the heading elements of an HTML file, e.g. <title> (the title bar element) <bgsound> (background sound file) <style> (links to style sheet files) <meta> (provides links for search engines) Except for <title> the other elements are not visible to the viewer Closing tag is </head> <title> Defines text displayed in tabs in the browser when the page is displayed Appears inside the <head> </head> block The <title> tag is a required element A title directly reflects a page s ranking in most search engines Closing tag is </title> <body> Encloses body elements of HTML file Elements that appear on the Web page <body> Closing tag is </body> The <img> (Image) Tag (Page 1) The src attribute must be used to name an image (graphic) file to be displayed on page Path is required if file is not located in same directory as the HTML document <img src="path/filename" /> <img src="images/sccclogob.jpg" /> The <img> (Image) Tag (Page 2) There is no closing tag for <img> so it should included a slash (/) meaning the end symbol inside the tag itself, e.g. <img /> Dragging an Image from Solution Explorer In either Source or Design view, the designer and drag an image from the Solution Explorer window into the document

9 CST141 ASP.NET Database Page 9 Creates an HTML <img> tag in the document Properties Window Window on the lower right of IDE where designer sets the properties (characteristics) for objects, controls, classes and other project components Properties can be updated: At design time by changing their values in the Properties Window By writing Visual C# assignment statements in the program code behind the page, e.g. TextBoxCity.Text = "New York"; Using the Style Attribute for Formatting CSS syntax and the style attribute can be used for the formatting of HTML elements To create a style attribute for absolute positioning of an element, e.g. <div style="position:absolute; top:200; left:200" /> Document Views The tabs at the bottom left of the Document window lets the designer select among the following views: Source view the actual ASP.NET code Design view an approximation of the Web page that the code will render in a browser Split view Source view in the upper window and Design view in the lower window Run the Web Site Running an ASP.NET Web Site application means to view it in a Web browser An application may be executed for testing by clicking the <Start debugging> button on the Standard toolbar Close the browser window to stop running It may be necessary to click the <Stop debugging> button ( ) on the toolbar after browser window closes ASP.NET Server Controls Controls are similar to Windows Forms controls ASP.NET controls are identified with the prefix asp: followed by the name of the control, plus a runat="server" attribute and value, e.g. <asp:textbox runat="server"> Some types of ASP.NET Server Controls ASP.NET Form Controls (Web controls) Data Validation Controls Data Controls Mobile Controls (run on mobile devices) The Toolbox Provides access to commonly used controls, e.g. the ASP.NET Server controls

10 CST141 ASP.NET Database Page 10 Can be hidden and made to slide out the Auto Hide feature Hover over the text Toolbox in the left side of the IDE window and it slides into view (the default mode for the Toolbox is hidden) Click the Auto Hide icon (push pin) to turn the feature on and off The ASP:SqlDataSource Web Control (Page 1) The asp:sqldatasource Web control is used to retrieve and modify (insert, update, and delete) data from a database with little or no code Can work with any database that has an associated ADO.NET provider E.g. Microsoft SQL Server, Oracle, ODBC, or OLE DB databases such as Microsoft Access The ASP:SqlDataSource Web Control (Page 2) The SqlDataSource requires that two properties be set (performed by clicking the smart tag and selecting the command Configure Data Source ): ConnectionString specifies the database type, location and filename Created automatically in the Web.config file the first time the SqlDataSource is linked to SqlServer database in the Configure Data Source wizard SelectCommand set to an SQL SELECT query Created automatically by using the Configure the Select Statement window of the wizard Data Source Configuration: New Data Source Switch to Design View and click the smart tag to access the Configure Data Source wizard: On the Configure Data Source window click the <New Connection > button In the Add Connection window, select Microsoft SQL Server Database File as the Data Source Click <Continue> and <Browse > to find database Select it and click the <Open> button Choose Yes, save the connection as to store the connection string in the Web.config file Click <Next> to go to next window of the wizard Data Source Configuration: Existing Connection String Switch to Design View and click the smart tag to access the Configure Data Source wizard: Select the Connection string associated with the desired database from the dropdown list of existing connection strings Click <Next> to go to next window of the wizard Build the SQL Select Statement (Page 1) The Configure the Select Statement step of wizard specifies how to create SELECT statement: Specify columns from a table or view:

11 CST141 ASP.NET Database Page 11 Select the table name and check the columns (fields) of data to be included in the SELECT query Further define the statement by using the <WHERE> and <ORDER BY> buttons The SELECT statement is visible under the heading SELECT statement: Click <Next> and then <Finish> buttons Build the SQL Select Statement (Page 2) The Configure the Select Statement step of wizard specifies how to create SELECT statement (con.): Specify a custom SQL statement or stored procedure: Click <Next> and then click the <QueryBuilder> button to access an intuitive user interface for creating the SELECT statement Click <Add> to add tables to query (then <Close>) Check columns for the query; then click <OK> Build the SQL Select Statement (Page 3) The Configure the Select Statement step of wizard specifies how to create SELECT statement (con.): Specify a custom SQL statement or stored procedure (con.): Finally click <Next> and then <Finish> buttons This tool is helpful especially when joining data from multiple tables The ASP:SqlDataSource Web Control for Inserting, Updating and Deleting Once the SELECT statement is specified Click the <Advanced> button which displays the Advanced SQL Generation Options dialog window Click on the checkbox for the Generate INSERT, UPDATE, and DELETE statements checkbox Adds InsertCommand, UpdateCommand, and DeleteCommand properties to <asp:sqldatasource> control tag The ASP:GridView Web Control (Page 1) Automatically binds to and displays data from a data source control in tabular view (rows and columns) To assign the data source: Click the smart tag and select a data source (e.g. an SQLDataSource object) from the Choose Data Source: drop-down list The source code is updated automatically to include a <Columns> block and <asp:boundfield> tags which represent the data (usually) This formats the columns to represent the fields of the selected query (the data source) The ASP:GridView Web Control (Page 2) When a data source is selected for the GridView control, the following of its properties are updated automatically:

12 CST141 ASP.NET Database Page 12 AutoGenerateColumns how are fields generated?: True from the data source at run-time False uses columns defined in <Columns> block DataKeyNames the DataField property of the BoundColumn(s) that uniquely identify each record (by default the primary key) DataSourceID the ID of its data source controls Customizing ASP:GridView Using AutoFormat Formats the GridView by allowing user to select from a series of predefined styles Click the smart tag for the GridView and click the AutoFormat command Select one of the predefined styles to preview it Click the <OK> button to implement the style The appropriate properties are set in the source code The SQL UPDATE Command (Page 1) Modifies values in an existing row (or rows) within a database table Not all fields need be updated UPDATE TableName SET field1 = value1/"string1"[, field2 = value2/"string2", ] [WHERE fieldname = value/"string"] value(s) may be numeric, Boolean, Date, etc The SQL UPDATE Command (Page 2) Examples: UPDATE Book SET Title = "Of Mice and Women", PublisherCode = "BB", Type = "FIC", Price = 12.59, Paperback =.F. WHERE BookCode = "7711" UPDATE Book SET Price = WHERE BookCode = "7711" 77 The SQL DELETE Command Deletes a row (or more than one row) from a database table DELETE FROM TableName [WHERE fieldname = value/"string"] DELETE FROM Book

13 CST141 ASP.NET Database Page 13 WHERE BookCode = "7711" SQL Parameters (Page 1) Visual Studio uses parameters to represent variable data in a parameterized SQL statement It is an object that can accept different values based upon the logic of the application The values are determined dynamically at run-time SQL Parameters (Page 2) When Generate INSERT, UPDATE, AND DELETE statements is selected, there are three parameter blocks inserted for each into the <asp:sqldatasource> tag: <InsertParameters> parameters used within the SQL Insert statement <UpdateParameters> parameters used within the SQL Update statement <DeleteParameters> parameters used within the SQL Delete statement SQL Parameters (Page 3) The properties for the <asp:parameter> tag include: Name used within the parameterized SQL statement Type data type which is a Visual C# type consistent with the type in the database Format: <asp:parameter Name="nameProperty" Type="dataType" /> Example: <asp:parameter Name="ProductID" Type="String" /> SQL Parameters (Page 4) A parameter is a variable in the form of a question mark (?) within a parameterized SQL statement Example of a parameterized SQL statement: <asp:sqldatasource DeleteCommand="DELETE FROM [Product] WHERE [ProductID] =?" > The question mark (?) is the parameter Editing Data with GridView (Page 1) In GridView records can be edited by adding an Edit command (button or link) within the CommandField column for each record When the button/link is clicked: The page is posted back and all editable fields (not the primary key or other fields set to be read-only) are converted to TextBoxes for updating During editing the Edit button is converted to two buttons, Update and Cancel Editing Data with GridView (Page 2) When the Update button is clicked: The page is posted back again The data source s UpdateCommand is executed The GridView retrieves that updated table from the data source and redisplays the

14 CST141 ASP.NET Database Page 14 data If the Cancel button is clicked: The page is posted back, but GridView is updated from the unmodified data source To configure GridView for editing, click smart tag and click on the Enable Editing checkbox Editing Data with GridView (Page 3) To configure GridView for editing records, click the smart tag and click to check on the Enable Editing checkbox Adds a <asp:commandfield> to the <Columns> block with the ShowEditButton property set to True <asp:commandfield ShowEditButton="True" /> <h1> through <h6> In HTML the <h1> through <h6> tags indicate a heading line and its level Largest font size is <h1>, smallest is <h6> Text displayed in bold font style Automatic double spacing also is implemented after the heading text Often used to indicate titles or to organize a page into sections Closing tags are </h1> through </h6> <p> In HTML divides text into paragraphs Automatic double spacing also is implemented within this tag Closing tag is </p> The ASP:TextBox Web Control (Page 1) The asp:textbox collects text input from users When the TextMode property is set to SingleLine, (default if not entered) creates a one-line textbox <asp:textbox ID="id" runat="server"> </asp:textbox> The ASP:TextBox Web Control (Page 2) Properties: (ID): the object s name Text: the text displayed in the text box (updated as a user keys new or updated text) The ASP:Label Control (Page 1) A Label control is an unattached text object that has a series of properties used for formatting The Text property stores the Label s text that appears on the web form The ASP:Label Control (Page 2) <asp:label ID="LabelID" runat="server" Text="Label Text" [formatting

15 CST141 ASP.NET Database Page 15 properties]></asp:label> <asp:label ID="Label1" runat="server" Text="Publisher Code:" Width="125"></asp:Label> The Button Web Control (Page 1) It functions as an HTML submit button (the form is submitted to the server) A form is most often submitted by clicking on a button The <asp:button> Web server control in ASP.NET has the following format: The control is used to display a push button The push button may be a submit button or a command button (by default it is a submit button) The Button Web Control (Page 2) A submit button does not have a command name and it posts the page back to the server when clicked It is possible to write an event handler to control the actions performed when the submit button is clicked A command button has a command name and allows the creation of multiple Button controls on a page It is possible to write an event handler to control the actions performed when the command button is clicked The Button Web Control (Page 3) <asp:button ID="ButtonID" runat="server" Text="Button Text" /> The Text property is the label displayed on the button A one-sided tag requires tag end character (/) inside it <asp:button ID="ButtonInsertPublisher" runat="server" Text="Insert Publisher" /> The Button Web Control (Page 4) The OnClick property links a Button to a Click event handler (a method) <asp:button ID="ButtonID" runat="server" Text="Button Text" OnClick="MethodName" /> <asp:button runat="server" ID="ButtonInsertPublisher" Text="Insert Publisher" OnClick="ButtonInsertPublisher_Click" /> Events and Event Handlers (Page 1) For almost every object on the Form, the browser can respond to many mouse and keyboard actions Some examples: Click, MouseDown, MouseMove, KeyPress, Validating, Validated

16 CST141 ASP.NET Database Page 16 The event handler for the object and its related event appears as a method within the.aspx.cs file (the C# code for the form) Events and Event Handlers (Page 2) To create event handlers for any control double-click on the object Default event for an asp:button is Click For each event handler method, this registers an OnClick property within the control that links it to the method, e.g.: <asp:button runat="server" ID="ButtonInsertPublisher" Text="Insert Publisher" OnClick="ButtonInsertPublisher_Click" /> Syntax of an Event Handler Header (Page 1) protected type methodname(object sender, EventArgs e) methodname by default consists of the concatenation of the object name and event type Event handler methods have two parameters: sender: a reference which identifies the object (control) which initiated the call to the method e: an object variable that stores property values and methods related to the event Syntax of an Event Handler Header (Page 2) protected type methodname(object sender, EventArgs e) { protected void ButtonInsertPublisher_Click(object sender, EventArgs e) { Manually Insert Values into a SqlDataSource Parameter Assign values to the individual InsertParameters in the collection using the DefaultValue property SqlDataSource.InsertParameters ["ParameterName"].DefaultValue = value; SqlDataSourceInsertPublisher.InsertParameters["PublisherCode"].DefaultValue = TextBoxPublisherCode.Text; The SQL INSERT Command (Page 1) Adds one record to a database table: INSERT INTO TableName VALUES (value1/"string1" [, value2/"string2", ]) The number of fields and data type (including in order) must match those in the database table

17 CST141 ASP.NET Database Page 17 value(s) may be numeric, Boolean, Date, etc The SQL INSERT Command (Page 2) INSERT INTO Book VALUES ("7711", "Of Mice and Men", "BB", "FIC", 10.99,.F.) The SqlDataSource Insert() Method Inserts a new record into the table represented by a SqlDataSource control A SelectCommand must have been configured Values must have been previously assigned all the InsertParameters for fields that require a value SqlDataSource.Insert(); SqlDataSourceInsertPublisher.Insert(); The Response.Redirect Method Causes the browser to redirect the client to (load) a different URL (web address) instead of reposting to itself Response.Redirect("WebAddress"); The WebAddress is a URL passed as a string Examples: Response.Redirect("PublisherTable.aspx); Response.Redirect(" The asp:detailsview Web Control (Page 1) The asp:detailsview displays the values of a single record one at a time from a data source Each row in the DetailsView control represents one field within the record <asp:detailsview ID = "ControlName" runat = "server"> </asp:detailsview> The asp:detailsview Web Control (Page 2) To assign the data source: Click the smart tag and select a data source (e.g. a SQLDataSource object) from the Choose Data Source: drop-down list The rows are formatted automatically to represent the fields of the selected query (data source) The source code is updated automatically to include a <Fields> block and <asp:boundfield> tags which represent the data The asp:detailsview Web Control (Page 3) When a data source is selected for the DetailsView control, the following of its

18 CST141 ASP.NET Database Page 18 properties usually are updated automatically: AutoGenerateColumns how are fields generated? (set to False): True generated from the data source at run-time False permanently defined in the <Fields> block The asp:detailsview Web Control (Page 4) When a data source is selected for the DetailsView control, the following of its properties usually are updated automatically (con.): DataKeyNames the DataField property of the BoundColumn(s) that uniquely identify each record (by default the primary key) DataSourceID the ID of its data source controls The asp:detailsview Web Control (Page 5) Formatting for the DetailsView control is similar to that of the GridView Easiest to use AutoFormat SqlDataSource: ORDER BY When configuring a SqlDataSource control, at the Configure the Select Statement dialog window: Click the <ORDER BY > button to get to the Add ORDER BY Clause dialog box for sorting the result of a SQL SELECT statement Specify up to three columns (fields) to sort the results Second and third columns used for intermediate and minor level sorts within the major sort To change sort order for any column to descending, select Descending option (ascending is default) The asp:dropdownlist Web Control (Page 1) The asp:dropdownlist Web control creates a Form field that allows users to select from drop-down lists of multiple options <asp:dropdownlist ID = "ControlName" runat = "server"> </asp:dropdownlist> The asp:dropdownlist Web Control (Page 2) The list (an Items collection) can be populated in from a data source: Assign the asp:dropdownlist s DataSourceID property to a SqlDataSource object (or some other data source) The easiest way is to use the smart tag (just like GridView and DetailsView) The asp:dropdownlist Web Control (Page 3) Properties for the asp:dropdownlist Web control with a data source: DataSourceID name of the SQLDataSource (or some other data source) that provides the items for the list DataTextField column from the SELECT list of the data source that is the text displayed for each item DataValueField column from the SELECT list of the data source that is the value

19 CST141 ASP.NET Database Page 19 (text) passed to the server for processing when an item is selected Query Strings (Page 1) A query string is part of a URL (web address) that used to send the values from one webpage to other page (like passing arguments) Consists of a series of key and value pairs The key is the variable name The value is a value assigned (=) to the key Multiple keys and values may be joined by using the ampersand (&) character and passed together in the same URL, e.g.: key1=value1[&key2=value2 ] Query Strings (Page 2) In a URL the key and value pairs follow the Web address and a question mark (?) symbol: ] Each of the key and value pairs are separated by an ampersand (&) symbol Query Strings (Page 3) Example when the file has the same path (location): PublisherDetail.aspx?PublisherCode=AH Passing a Query String Through the Response.Redirect Method A query string may be included within the string argument of the Response.Redirect() method Response.Redirect("WebAddress?key1=value1[&key2=value2 " ]); Examples: Response.Redirect(" com/publisherdetail.aspx?publishercode=ah"); Response.Redirect("PublisherDetail.aspx? PublisherCode=AH"); The SelectedValue Property for the DropDownList Control The SelectedValue property represents the text assigned to the Value property for the currently selected item of the DropDownList control DropDownListControlID.SelectedValue DropDownListPublisher.SelectedValue Using the SelectedValue in a QueryString The SelectedValue property of a DropDownList may be used to customize the value element in a query string

20 CST141 ASP.NET Database Page 20 Response.Redirect("PublisherDetail.aspx?PublisherCode=" + DropDownListPublisher.SelectedValue); QueryStringParameters in SELECT Command of SqlDataSource (Page 1) A QueryStringParameter for a SQL SELECT command automatically retrieves values from the query string When configuring the SqlDataSource: Click the <WHERE > button and select the Column (field) for the WHERE clause and the Operator From the Source drop down list select Query String Enter the key name from the query string into the QueryString field textbox QueryStringParameters in SELECT Command of SqlDataSource (Page 2) Process inserts an asp:querystringparameter into SqlDataSource s <SelectParameter> block As opposed to an asp:insertparameter Sets its QueryStringField property to the query string key Additionally inserts a WHERE clause with the parameter into the SELECT statement QueryStringParameters in SELECT Command of SqlDataSource (Page 3) <SelectParameters> <asp:querystringparameter Name="PublisherCode" QueryStringField="PublisherCode" Type="String" /> </SelectParameters> The Request.QueryString Method Retrieves (returns) the collection of key and value pairs from an HTTP query string Request.QueryString["keyName"] The keyname is a string which is the name (key) as assigned when the original query string created by the Response.Redirect method String publishercode = Request.QueryString["PublisherCode"]