PROG11044 - Advanced Web Apps 2/24/2019 Session 9.2 Data Binding Wendi Jollymore, ACES

Review Repeater control A control that repeats a set of controls and/or formatting You define what each row should look like <ItemTemplate></ItemTemplate> The control is bound to a data source The template is repeated for each set of data E.g. for each element of an array or hash table 2/24/2019 Wendi Jollymore, ACES

Review Repeater.DataSource property Repeater.DataBind() method Contains the name of or reference to a data source E.g. the name of a hash table, the name of an array variable, or the name of a DataSet object Repeater.DataBind() method Retrieves the data from the data source and re-populates the control with that data DataSource and DataBind() are common to the various data-bound controls in ASP.NET E.g. DataList, GridView, FormView, etc. 2/24/2019 Wendi Jollymore, ACES

Review Container.DataItem Refers to a data item in the container (template, in this case) Depends on the source of the data E.g. if the source is an array of strings, then DataItem is a String E.g. if the source is a hash table, then DataItem is one element of the hash table 2/24/2019 Wendi Jollymore, ACES

Review DictionaryEntry class Models a piece of data with a key/value pair Example: A hash table element Key property that contains the key portion Value property for value 2/24/2019 Wendi Jollymore, ACES

Review Container.DataItem from a hash table: We need to get the element’s key and value Cast Container.DataItem into a DictionaryEntry object DictionaryEntry.Key DictionaryEntry.Value 2/24/2019 Wendi Jollymore, ACES

Review Inline data binding expression: <%# … %> .Key or .Value <%# ((DictionaryEntry)Container.DataItem).Key %> <%# … %> Special inline syntax for data binding expression ((DictionaryEntry)Container.DataItem) Cast Container.DataItem into DictionaryEntry object .Key or .Value Reads the key or value property of the hash table element 2/24/2019 Wendi Jollymore, ACES

Repeater Templates ItemTemplate AlternatingItemTemplate The template for each item in the repeater You can put HTML, text, inline code, and other controls in here AlternatingItemTemplate You can make every other row look different E.g. different background colour 2/24/2019 Wendi Jollymore, ACES

Repeater Templates HeaderTemplate FooterTemplate The header! What appears once at the top of the repeater FooterTemplate The footer! What appears once at the bottom of the repeater For more templates, see the DataList control 2/24/2019 Wendi Jollymore, ACES

Repeater Templates Try it out! Make up a hash table with key/value data E.g. myData[“prog10082”] = “OOP 1”; Create a repeater control Header  open table tags and header row of table Footer  add footer row and closing table tags Continued… 2/24/2019 Wendi Jollymore, ACES

Repeater Templates ItemTemplate: Opening and closing <tr></tr> tags Two sets of <td></td> tags First cell for key Second cell for value <ItemTemplate><tr><td>…</td> <td>…</td></tr></ItemTemplate> 2/24/2019 Wendi Jollymore, ACES

Repeater Templates AlternatingItemTemplate Just like ItemTemplate Add to <tr>: bgcolor=“silver” Or whatever colour you like Everything else is the same 2/24/2019 Wendi Jollymore, ACES

Repeater Templates Data binding expression to go inside first set of <td></td>: <%# ((DictionaryEntry)Container. DataItem).Key %> Data binding expression to go inside second set of <td></td>: DataItem).Value %> 2/24/2019 Wendi Jollymore, ACES

Don’t forget to add using System.Collections; Binding the Repeater Page Load event: If this is not a postback, do these things: Create your hash table (just hard-code it) Assign your hash table object variable to the repeater’s DataSource Invoke repeater’s DataBind() Don’t forget to add using System.Collections; 2/24/2019 Wendi Jollymore, ACES

Binding to XML Data Make up an XML File: <bookmarks> <siteName></siteName> <url></url> </bookmark> … </bookmarks> Add new XML to project. Fill in data with whatever sites you want. 2/24/2019 Wendi Jollymore, ACES

DataSets System.Data.DataSet class A cool way to store data in rows and columns DataSet.ReadXml(“xmlFile.xml”) Reads in a valid XML file Stores XML data in a table Will use the XML element names as column names Each <bookmark></bookmark> node will be one record 2/24/2019 Wendi Jollymore, ACES

DataSets from XML Files The data is stored in rows or records The XML element names become the column/field names siteName url “Terminal Learning” http://www.TerminalLearning.com “Pogo” http://www.pogo.com “Bookcrossing” http://www.bookcrossing.com 2/24/2019 Wendi Jollymore, ACES

DataSets from XML Files Make a new project: Add a repeater control and set up a header and item template Header should say “Bookmarks” and formatted however you like Item template contains a single hyperlink server control The link will be an actual link to each bookmark entry in your XML file 2/24/2019 Wendi Jollymore, ACES

Data Binding Expression Eval() method An alternate way of data binding Much more efficient Great to use if you have field names! <%# Eval(“[fieldName]”) %> If you know the name of the data field For the hyperlink control: Add attribute NavigateUrl=‘<%# Eval(“[url]”) %>’ Text between tags: <%# Eval(“[siteName]”) %> 2/24/2019 Wendi Jollymore, ACES

DataSets from XML Files Code: Using System.Data; Page Load: All this is done if this is not a postback Create a new DataSet object Read the XML file into the data set DataSet myData = new DataSet(); myData.ReadXml(MapPath(“bookmarks.xml”)); MapPath() just makes sure you’re using the application path 2/24/2019 Wendi Jollymore, ACES

DataSets from XML Files Page Load, continued Assign the data set object to the repeater’s DataSource Invoke repeater’s DataBind Try loading the page… 2/24/2019 Wendi Jollymore, ACES

Exercise Do the Data Binding tutorial in the notes Very similar to previous two exercises Adds some functionality with check boxes! Note the little blue box about formatting! That’s a hint for Assign 1 2/24/2019 Wendi Jollymore, ACES