Session 9.2 Data Binding

1. Session 9.2 • Data Binding

2. 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 Wendi Jollymore, ACES

3. Review • Repeater.DataSource property • 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. Wendi Jollymore, ACES

4. 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 Wendi Jollymore, ACES

5. 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 Wendi Jollymore, ACES

6. 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 Wendi Jollymore, ACES

7. Review • Inline data binding expression: <%# ((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 Wendi Jollymore, ACES

8. Repeater Templates • ItemTemplate • 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 Wendi Jollymore, ACES

9. Repeater Templates • HeaderTemplate • 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 Wendi Jollymore, ACES

10. 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… Wendi Jollymore, ACES

11. 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> Wendi Jollymore, ACES

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

13. 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>: <%# ((DictionaryEntry)Container. DataItem).Value %> Wendi Jollymore, ACES

14. 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; Wendi Jollymore, ACES

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

16. 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 Wendi Jollymore, ACES

17. DataSets from XML Files • The data is stored in rows or records • The XML element names become the column/field names Wendi Jollymore, ACES

18. 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 Wendi Jollymore, ACES

19. 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]”) %> Wendi Jollymore, ACES

20. 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 Wendi Jollymore, ACES

21. 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… Wendi Jollymore, ACES

22. 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 Wendi Jollymore, ACES