This lecture presents how to create custom server controls

1. ASP.NET 4.0
Julie Iskander
MSC. Communication and Electronics

2. Lecture Outlines
 Custom Server Controls

3. Custom Server Controls
 Why use them?
◦ Complete control over rendered HTML
◦ Better design-time support
 More difficult then User Controls

4. Custom Server Control
 Inherits System.Web.UI.Control
◦ Provides common properties and methods
◦ Ex. ID, ViewState, Controls
 Sometimes inherits from
System.Web.UI.WebControls.WebContr
ol
◦ Adds more features to implement styles
◦ Ex. Font, ForeColor , BackColor

5. Creating a Completely Custom
Control
 Steps:
1. Create a new ASP.NET Server Control
Project
1. Add a new class derive from Control
2. Override Render() method
 Use HTTPTextWriter to write the wanted HTML.
2. In your website:
1. Add reference to the custom control assembly
(.dll)
2. Register assembly (.dll) in page
3. Register assembly (.dll) in web.config
4. Add the item to the Toolbox
5. Use in page

6. Step 1

8. Convert from an HTML to an aspx page

9. The Rendering Process

10. Styling custom Controls
 Better inherit WebControl
 Don’t overrride Render()
 Specify base tag of your control in
constructor
 Add public properties
 Initialize Properties by overriding OnInit()
 Override AddAttributeToRender() to add
the wanted attribute values
 Override RenderContent() to add the
wanted content

12. Convert from an HTML to an aspx page

13. View State
 To save and retrieve property values
in the view state
 To store information of the control
between postbacks.

15. Convert from an HTML to an aspx page

16. Postback Data and Change
Event
 To process the data that’s posted to
the page.
 Implement IPostBackDataHandler
◦ LoadPostData() called on page
postback before any control event
handling, to update control state
◦ RaisePostDataChangedEvent() to fire
events
◦ The control must have a name attribute
for postback to work

20. Convert from an HTML to an aspx page

21. Triggering a PostBack
 Is supported by a JavaScript function
named __doPostBack();
 Override AddAttributesToRender()
 Add a javascript event attribute to the tag
 The value is set using
Page.ClientScript.GetPostBackEventReference
()

23. Convert from an HTML to an aspx page

24. Controls Property
 A collection of childern controls to be
added to the control rendered with
RenderChild()

25. Convert from an HTML to an aspx page

26. Lab #6
 Create a custom control
◦ A labeled textbox with onTextChange
event of the textbox and a Text attribute
for the label. The data must be retained
between postbacks.
◦ Use it in register.aspx

27. Report #6
 What is control state of a control?

28. REFERENCES
 [1] Beginning ASP.NET 4 In C# 2010, Matthew
Macdonald, Apress
 [2] Web Application Architecture Principles,
Protocols And Practices, Leon Shklar And Richard
Rosen, Wiley
 [3] Professional AS P.NE T 4 In C# And VB, Bill
Evjen, Scott Hanselman And Devin Rader, Wiley
 [4] Pro ASP.NET In C# 2010, Fourth
Edition,matthew Macdonald, Adam Freeman, And
Mario Szpuszta, Apress