1 / 82

Data-Aware Controls in ASP.NET ® Applications

Data-Aware Controls in ASP.NET ® Applications. ASP.NET. Data Binding Techniques . A data source represents data A simple hash table, an array, or a database (or any other collection) Web controls are used to display the data

lel
Download Presentation

Data-Aware Controls in ASP.NET ® Applications

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Data-Aware Controls in ASP.NET® Applications ASP.NET

  2. Data Binding Techniques • A data source represents data • A simple hash table, an array, or a database (or any other collection) • Web controls are used to display the data • Sometimes called Data controls because their primary function is to display data • Displayed in a simple list, drop-down list, or table • Data binding is the process of assigning a data source to a Web control • Data can be bound to a variety of Web controls

  3. Data Binding Techniques

  4. SingleBind.aspx

  5. Single-Expression Binding (Page 1) • Binds a single value or expression to a control/tag • Enclosed within inline server tags, i.e. (<% %>) • Pound/digit symbol (#) before the expression name • Expression is a call to some named procedure, either programmer-defined or built-it (i.e. method or function) • The return value is inserted into the control • Example: <asp:Image id="Logo" AlterateText="Logo" ImageUrl="<%# GetImageURL %>" runat="server" />

  6. Single-Expression Binding (Page 2) • The server tag and expression may be entered into for many property lines in the Properties window for Web Server controls (not HTML controls) • When the (DataBindings) property is selected, the "DataBindings" dialog window is displayed • Enter the server tag expression into the Custom Binding Expression: window which names the command to execute • The radio button must be selected to enter an expression • Call DataBind() method usually from Page_Load event to bind the expression to each object

  7. Assign Property Value Directly

  8. Assign as a Data Binding

  9. Key Entry into HTML View

  10. Repeated-Expression Binding (Page 1) • Repeated expressions are bound to data controls (controls that have a DataSource property) • Could be a collection such as a HashTable, or an ArrayList (i.e. Chapter 4) • DataSet, DataTable, DataView, or DataReader from a database also are repeated expressions • CheckBoxList, RadioButtonList, DropDownList and ListBox inherit from ListControls class and may have data from any of the datasources above bound to them

  11. Repeated-Expression Binding (Page 2) • Data sources also may to bound to the DataGrid and DataList controls which are data controls that inherit from class BaseDataList • Repeater inherits from System.Web.UI.Controls class directly

  12. Repeated-Expression Binding

  13. ASP.NET Data Objects • DataSet • A cached (off-line) set of records from a database • Contains one or more DataTables • DataTable and DataView • Subset of rows of data from a DataSet • DataReader • Read-only, forward-only on-line stream of data from a database

  14. Data Binding Web Controls • DropDownList—displays one value at a time using the <select> tag; drops-down to display values • ListBox—displays values in a box several lines at a time using <select> tag • RadioButtonList and CheckBoxList—groups multiple controls • Repeater—small, lightweight control that displays data; repeats defined HTML content • DataList—displays data from each data row in a list • DataGrid—repeats content once for each data row; places the data in a table of rows and columns

  15. The DataSource Property • For data-aware controls, names the set of data to be displayed by the control • Format: controlName.DataSource = arrayList/hashTable/DataSet/DataView • Example: ddProducts.DataSource = arrayList1 • If a HashTable is assigned to DataSource property: • "Key" is the first element from the hash table • "Value" is the second element from the hash table

  16. The DataBind Method • Binds one or more data-aware controls so that data is linked to and displayed in the control • Format: Page/controlName.DataBind • The Page object may be used to bind all objects when there are more than one on the Web Form • Examples: ddProducts.DataBind() Page.DataBind() DataBind()

  17. DropDownList.aspx

  18. The DataTextFormatString Property (Page 1) • Provides formatting for elements in DataBound controls • Format string is in two parts, separated by a colon: {"A:Bxx"} • A specifies the index in a zero-based list of parameters (always 0 because there is only one value per element) • B specifies the format to display (C is currency, D is decimal, F is fixed, etc.) • xx specifies the number of decimal places to display

  19. The DataTextFormatString Property (Page 2) • Example: • {0:F2} • Formats element to display a fixed point number with two decimal places • Advisable to always specify decimal positions to make it easier for other programmers to read your code

  20. Other Properties of Bound Controls • DataTextField property—text displayed between or associated with the tag block or element • DataValueField property—used by the control as the value attribute

  21. Binding Data to DropDownList Control • Creates an HTML <select> … </select> block with <option> tags • Sets the size attribute (height of the object) in the HTML code sent to the browser as equal to 1 • The value 1 is the default for a dropdown list and will not actually be specified in the HTML • Example: <asp:dropdownlist id="ddProducts" runat="server"></asp:dropdownlist>

  22. ListBox.aspx

  23. Binding Data to a ListBox Control • Creates an HTML <select> … </select> block with <option> tags • Sets the size attribute (height of the object) in the HTML code sent to browser to a value greater than 1 • Example: <asp:listbox id="lbProducts" runat="server"></asp:listbox>

  24. CheckBoxRadio.aspx

  25. Binding Data to the CheckBoxList and RadioButtonList Controls • RadioButtonList and CheckBoxList also are data-aware controls • Each item in series (of CheckBoxes or RadioButtons) is created is an HTML <input> tag with the type attribute equal either "checkbox" or "radio" • Example: <asp:checkboxlist id="MyCBL1" runat="server"></asp:checkboxlist> <asp:radiobuttonlist id="MyRBL1" runat="server"></asp:radiobuttonlist>

  26. Binding to a DataGrid Control • Creates a grid of rows and columns to display two-dimensional data arrays, i.e. • It might display separate key and value items of a hash table in two columns, each element in its own row • Ideal for displaying records and fields from a database table, view or stored procedure • Once the data set exists, set the DataSource property of the DataGrid and call the DataBind() method • Example: <asp:DataGrid id="dgProducts" runat="server"></asp:DataGrid>

  27. DataGridSimple.aspx

  28. The AutoGenerateColumns Property of the DataGrid Control • Specifies whether of not columns in the grid are automatically created from the DataSource when the page loads • By default all columns are displayed in a DataGrid since the AutoGenerateColumns properties is set to True • If set to False, the <Columns> … </Columns> block must be used with <asp:BoundColumns> tags to name fields to display from DataSource • Required when using a HashTable since DataGrid does not have DataTextField and DataValueField properties

  29. The <Column> Control • When configuring a data source (i.e. HashTable, DataSet, DataView) programmatically, the DataGrid columns are not created until the code executes • The <Columns> … </Columns> control block can be added manually to the HTML view to build columns • Format: <Columns> columnElements </Columns>

  30. The <asp:BoundColumn> Control (Page 1) • Displays only selected items from data source in the columns of a DataGrid or other object • One or more controls are embedded in the <Columns> … </Columns> block • Properties: • DataField—names field for display from data source • HeaderText—text displayed at top of column • DataFormatString—uses the same format syntax as the DataTextFormatString

  31. The <asp:BoundColumn> Control (Page 2) • Example: <Columns> <asp:BoundColumn DataField="Value" HeaderText="Price" DataFormatString="{0:C}"> </asp:BoundColumn> <asp:BoundColumn … </Columns>

  32. Setting DataGrid Formatting • Found in the Properties window, separate formatting is available for: • HeaderStyle • ItemStyle • FooterStyle • Also may be keyed manually in the HTML view • Be careful to not enter the <ItemStyle> tag inside a <Column> … </Column> block • Such an error would cause the style of just that one column to be formatted

  33. Binding to a DataList Control • Used to create a simple, one-dimensional list • An <ItemTemplate> control is required in DataList to identify the columns to display and to format data • Like a loop that formats every line in the DataList or other object • Templates are used to store data binding instructions • Example: <asp:DataList id="dlProducts" runat="server"> ItemTemplateInformation </asp:DataList>

  34. DataList.aspx

  35. Templates (Page 1) • Templates • Binds data to individual areas within the control providing the ability to format the control • Combines content, HTML, styles, return values of methods and formatting elements into a single column • May be used in a DataGrid to create an HTML stream of characters • An ItemTemplate is required for the DataList and Repeater controls • Information will be displayed one time for each row/element in the DataSource, like a loop)

  36. Templates (Page 2) • Types: • HeaderTemplate—modifies content and appearance of data in header section (first row) • ItemTemplate—configures data rows; <img> and many other HTML elements may be included as well as data source items • FooterTemplate—configures data in footer section (last row) • SeparatorTemplate—configures elements that appear between each of the items • EditItemTemplate—modifies configuration of columns or rows that currently are being edited

  37. Templates (Page 3) • Example: <asp:DataList id="dlProducts" runat="server"> <ItemTemplate> <b><%# Container.DataItem.Value %></b> : <%# Container.DataItem.Key %><br> </ItemTemplate> </asp:DataList>

  38. The Container.DataItem Function • A server expression used in a template to identify the columns to bind to a control • Retrieves and stores values, and places them into the HTML output stream • Format: Container.DataItem("fieldNameString") • Examples: <%# Container.DataItem("ProductId") %> <%# Container.DataItem.Key %> • In the second example, the key (first) element from a hash table is the bound data item

  39. The DataBinder.Eval Function • A server expression used in a template that, in a single statement,identifies the columns to bind to control along with the formatting instructions • Like Container.DataItem function, retrieves values and places them into the HTML output stream • Format for data-aware controls: DataBinder.Eval(Container.DataItem, "fieldName", "dataFormatString") • Example: <%# DataBinder.Eval(Container.DataItem, "Value", "{0:C}") %>

  40. Binding Data to a Repeater Control (Page 1) • Used to create tables, comma-delimited lists, bulleted lists, and numbered lists • Has no default appearance so it must be configured in HTML view • Data can be inserted with: • An HTML <table> tag • ASP.NET templates include header, footer, alternating, item and separator templates • To position a Repeater control, use the HTML <div> tag or an ASP.NET Panel control

  41. Repeater.aspx

  42. Binding Data to a Repeater Control (Page 2) • Example: <asp:Repeater id="Repeater1" runat="server"> ItemTemplateInformation </asp:Repeater>

  43. The ADO Objects • There are five (5) objects that must be declared: • Connection (OleDbConnection) • DataAdaptor (OleDbDataAdaptor) • Command (OleDbCommand) • DataSet • DataTable or DataView

  44. The OleDbConnection Object • A programmer-defined identifier which defines the connection to a database file • Stores connection information (ConnectionString property) including the DBMS type, as well as the path and filename of database • Format: DimobjectNameAs NewOleDbConnection • Example: Dim conTaraStore As New OleDbConnection • Prefix for OleDbConnection objects is "con"

  45. The OleDbDataAdaptor Object • A programmer-defined identifier (in this case a reference variable/object) • Performs the operations required to communicate between an ASP.NET application and a database file • Format: DimobjectNameAs NewOleDbDataAdaptor • Example: Dim daProducts As New OleDbDataAdaptor • Prefix for OleDbDataAdaptor objects is "da"

  46. The OleDbCommand Object • A programmer-defined identifier which stores the SQL command information that must execute to establish the database connectivity • Stores a command (CommandText property) that may returns specific records • Or store commands to insert, update or delete rows • Format: DimobjectNameAs NewOleDbCommand • Example: Dim cmdProducts As New OleDbCommand • Prefix for OleDbCommand objects is "cmd"

  47. The DataSet Object • Programmer-defined identifier (reference variable) which stores the collection of tables … • The object may store more than one table returned by the OleDbDataAdaptor object • Tables literally are stored off-line in RAM • Format: Dim/PrivateobjectNameAs NewDataSet • Example: Dim dsProducts As New DataSet • Prefix for DataSet objects is "ds"

  48. The DataTable Object (Page 1) • Programmer-defined identifier which stores a reference to a single table from a DataSet that is stored in RAM • The data then is manipulated off-line • The physical database on disk may be updated after the processing of the data is completed • The DataTable object points to one of the tables from the DataSet object

  49. The DataTable Object (Page 2) • Format: Dim/PrivateobjectNameAs DataTable • Example: Dim dtProducts As DataTable • The reserved word New is not used because the object variable is a pointer (points to an address in RAM) • Prefix for DataTable objects is "dt"

  50. Importing a Namespace (Page 1) • Use of the keyword Imports lets developer reference a namespace element from the .NET framework without fully qualifying the element • Statement must appear at the top of a module before the class header ("Public Class … ") usually after the Option Explicit and Option Strict statements

More Related