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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

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data binding techniques
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
single expression binding page 1
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" />

single expression binding page 2
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
repeated expression binding page 1
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
repeated expression binding page 2
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
asp net data objects
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
data binding web controls
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
the datasource property
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
the databind method
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()

the datatextformatstring property page 1
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
the datatextformatstring property page 2
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
other properties of bound controls
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
binding data to dropdownlist control
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>

binding data to a listbox control
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>

binding data to the checkboxlist and radiobuttonlist controls
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>

binding to a datagrid control
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>

the autogeneratecolumns property of the datagrid control
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
the column control
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>

the asp boundcolumn control page 1
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
the asp boundcolumn control page 2
The <asp:BoundColumn> Control (Page 2)
  • Example:

<Columns>

<asp:BoundColumn DataField="Value"

HeaderText="Price"

DataFormatString="{0:C}">

</asp:BoundColumn>

<asp:BoundColumn …

</Columns>

setting datagrid formatting
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
binding to a datalist control
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>

templates page 1
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)
templates page 2
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
templates page 3
Templates (Page 3)
  • Example:

<asp:DataList id="dlProducts" runat="server">

<ItemTemplate>

<b><%# Container.DataItem.Value %></b>

: <%# Container.DataItem.Key %><br>

</ItemTemplate>

</asp:DataList>

the container dataitem function
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
the databinder eval function
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}") %>

binding data to a repeater control page 1
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
binding data to a repeater control page 2
Binding Data to a Repeater Control (Page 2)
  • Example:

<asp:Repeater id="Repeater1" runat="server">

ItemTemplateInformation

</asp:Repeater>

the ado objects
The ADO Objects
  • There are five (5) objects that must be declared:
    • Connection (OleDbConnection)
    • DataAdaptor (OleDbDataAdaptor)
    • Command (OleDbCommand)
    • DataSet
    • DataTable or DataView
the oledbconnection object
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"
the oledbdataadaptor object
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"
the oledbcommand object
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"
the dataset object
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"
the datatable object page 1
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
the datatable object page 2
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"
importing a namespace page 1
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
importing a namespace page 2
Importing a Namespace (Page 2)
  • Format:

Imports Namespace.Namespace.etc.

  • If "OleDbConnection" class is in System.Data.OleDb namespace the following Imports statement lets the class be called directly:

Imports System.Data.OleDb

Dim conTaraStore As New OleDbConnection

  • Instead of:

Dim conTaraStore as New System.Data.OleDb.OleDbConnection

linking the objects page 1
Linking the Objects (Page 1)
  • There are six (6) steps necessary to create the links between the objects and access the database:
    • Assign a string to the ConnectionString property of the OleDbConnection object:
    • Assign a SQL string to the CommandText property of the OleDbCommand object
    • Assign the Connection object as the Connectionproperty of the Command object
    • Assign Command object as the SelectCommand property of the DataAdaptor object
linking the objects page 2
Linking the Objects (Page 2)
  • The six (6) steps necessary to create links between the objects and access the database (con.):
    • Call the Fillmethod of the DataAdaptor object with the DataSet object as its argument
    • Assign the Tablesproperty of the DataSet object to the DataTable object with the first returned table
the connectionstring property page 1
The ConnectionString Property (Page 1)
  • For the OleDbConnection object, builds a String which establishes the filename and other connection arguments to the data source
  • The information items is in the form of key=value pairs each separated by a semicolon (;)
  • The Provider string specifies the DBMS type, i.e.

"Provider=Microsoft.Jet.OLEDB.4.0"

  • The Source string specifies path (location) to the database and its filename, i.e.

"Data Source=c:\TaraStore.mdb"

the connectionstring property page 2
The ConnectionString Property (Page 2)
  • Format:

ConnectionObjectName.ConnectionString = "ProviderString;SourceString"

  • Example:

mconPayables.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=c:\TaraStore.mdb"

the commandtext property
The CommandText Property
  • For the OleDbCommand object, a String that defines the SQL SELECT, INSERT, UPDATE, or DELETE command
  • Format:

CommandObjectName.CommandText = "SQLCommandString"/StringVariable

  • Example:

pcmdVendor.CommandText = "SELECT * FROM Products"

the connection property
The Connection Property
  • For the OleDbCommand object, stores information about the DBMS to which the command references
  • Effectively creates the link between the Command object and the Connection object
  • Format:

CommandObjectName.Connection = ConnectionObjectName

  • Example:

cmdProducts.Connection = conTaraStore

the selectcommand property
The SelectCommand Property
  • For the OleDbDataAdaptor object, stores SQL SELECT command information to be executed by the DBMS
  • Effectively creates a link between the DataAdaptor object and the Command object
  • Format:

DataAdaptorObjectName.SelectCommand = CommandObjectName

  • Example:

daProducts.SelectCommand = cmdProducts

the fill method
The Fill Method
  • A method of OleDbDataAdapter objects which:
    • Opens the connection to the data provider (DBMS)
    • Sends the SQL SELECT command
    • After the data provider executes the command, populates DataSet with table data from database
  • Format:

DataAdapterObjectName.Fill (DataSetObjectName)

  • Example:

daProducts.Fill(dsProducts)

the tables collection page 1
The Tables Collection (Page 1)
  • A member of the DataSet object representing the one or more tables assigned to it
  • A collection is an array of properties for an individual object
  • The Tables collection is the set of tables that is stored in the DataSet object and may include one or more tables
the tables collection page 2
The Tables Collection (Page 2)
  • Format:

DataSetObjectName.Tables(index)

  • Example:

mdtVendor = mdsVendor.Tables(0)

    • Here one table from the DataSet collection is assigned to a DataTable object
    • The index "0" is the first table from the DataSet (points to a table)
modifying data columns in the datagrid control page 1
Modifying Data Columns in the DataGrid Control (Page 1)
  • By default all columns are displayed in a DataGrid since the AutoGenerateColumns properties is set to True
  • When configuring a data source (DataSet, DataTable, or DataView) programmatically, the DataGrid columns are not created until the code executes
modifying data columns in the datagrid control page 2
Modifying Data Columns in the DataGrid Control (Page 2)
  • The <Columns> … </Columns> control block can be used to add columns manually to the HTML view
    • Set DataField property for each <asp:BoundColumn> to fieldname from the table
    • Modify HeaderText property for each column to vary it from default string which is fieldname
  • Example:

<Columns>

<asp:BoundColumn DataField="CategoryName" HeaderText="Name"></asp:BoundColumn>

<asp:BoundColumn …

</Columns>

the itemstyle control page 1
The <ItemStyle> Control (Page 1)
  • Columns have a header, footer, and item section
  • When the <ItemStyle> control is embedded in an <asp:BoundColumn>, developer may format that column for every row in the table by setting properties and values using IntelliSense
  • Inserted into either:
    • The <asp:DataGrid> … </asp:DataGrid> block format all columns in all rows (but not headers and footers)
    • The<asp:BoundColumn> … </asp:BoundColumn> block to format individual columns
the itemstyle control page 2
The <ItemStyle> Control (Page 2)
  • Example:

<asp:BoundColumn DataField="CategoryName" HeaderText="Name">

<ItemStyle Font-Names="Trebuchet MS" ForeColor="DarkSlateGray"></ItemStyle>

</asp:BoundColumn>

the property builder for the datagrid page 1
The Property Builder for the DataGrid (Page 1)
  • Style template controls (<HeaderStyle>, <ItemStyle>, etc.) may be inserted into the HTML code for a DataGrid using the Property Builder
  • If data source configured programmatically, remember to first create a <Column> … </Column> block with <asp:BoundControl> controls in the HTML view
the property builder for the datagrid page 2
The Property Builder for the DataGrid (Page 2)
  • Right click on the DataGrid and select Property Builder… from the shortcut menu
  • Select the Columns tab to add columns to and/or modify existing columns in the DataGrid control
    • Modify each column’s HeaderText, DataField, and other attributes here
    • A <asp:BoundColumns> control should appear in the Select columns: list for each column
the property builder for the datagrid page 3
The Property Builder for the DataGrid (Page 3)
  • Select the Format tab to modify the appearance of template items, including:
    • Header and Footer (top and bottom of grid), and Pager (controls that link to previous and next pages in DataGrid)
    • Items—adds formatting for rows within the <asp:DataGrid> … </asp:DataGrid> block including Normal (formats <ItemStyle> control for all columns)
    • Columns—drill down clicking the plus (+) in each column to reach its Header and Footer (for each column) or Items (the cells) elements
      • Select the column name to modify its width attribute
displaygridcolumns aspx property builder properties page 1
DisplayGridColumns.aspx—Property Builder Properties (Page 1)
  • Columns tab
    • CategoryName—HeaderText: "Name"
    • CategoryID—HeaderText: "Category ID"
displaygridcolumns aspx property builder properties page 2
DisplayGridColumns.aspx—Property Builder Properties (Page 2)
  • Format tab
    • Header
      • BackColor: DarkSlateGrey
      • Bold: True
      • Font name: Trebuchet MS
      • ForeColor: White
      • Horizontal alignment: Center
    • Items—Normal Items
      • Font name: Trebuchet MS
      • Font size: X-Small
    • Columns—Columns(0)—Items
      • Horizontal align: Center
data columns
Data Columns
  • All of the following are column types that may be inserted within a <Columns> … </Columns> block to assign columns to a DataGrid:
    • BoundColumn—binds the column to one field from a data source
    • TemplateColumn—customized columns; can be used for formatting how entries appear both while both displaying and editing data in a DataGrid control
    • HyperLinkColumn—displays and creates a hyperlink (may be configured in the Property Builder)
the hyperlinkcolumn
The HyperLinkColumn
  • In place ofNavigateURL, the following attributes may be used to pass a query string to a called page
    • DataNavigateUrlFormatString attribute—the format of a URL with a query string that may store a variable value
    • DataNavigateUrlField attribute—stores a value which can be passed along with the key as part of the query string
  • Example:

<asp:HyperLinkColumn DataTextField="ModelName" DataNavigateUrlField="ProductID" DataNavigateUrlFormatString="Products.aspx?ProductID={0}">

column styles
Column Styles
  • These templates may be modified manually in the HTML view, or by using the Property Builder
    • HeaderStyle—formats the HeaderTemplate
    • FooterStyle—formats the FooterTemplate
    • ItemStyle—formats individual columns in every row
    • AlternatingItemStyle—formats every other row
    • SelectedItemStyle—formats currently selected row
    • EditItemStyle—formats the row in edit mode
    • PagerStyle—formats the page navigation controls
      • PageSize—stores the number of rows number displayed
additional properties for the datalist control
Additional Properties for the DataList Control
  • RepeatColumns property—an integer which specifies the number of columns that may be displayed in the DataList for each of the <ItemTemplate> elements
  • RepeatDirections property—direction of repetition for the RepeatColumns property in <ItemTemplate> columns within the grid
    • RepeatDirection.Horizontal
    • RepeatDirection.Vertical