Asp.NET Core Server Controls

1. Asp.NET Core Server Controls

2. Lecture Overview • Understanding the types of ASP.NET controls • HTML controls • ASP.NET (Web) controls

3. The runat Attribute • The runat attribute makes a server control a server control • This is true for both HTML and Web controls • All tags without the runat attribute set are copied verbatim to the output stream (HTTP response) • <asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>

4. Categorizing Server Controls ASP.NET CONTROLS WEB CONTROLS HTML CONTROLS

5. Categorizing Server Controls • HTML controls • always map to HTML tags • All attributes are strictly compatible with XHTML • They allow you to perform ‘some’ server side processing • Web Controls (ASP.NET server controls) • Are implemented by the ASP server as .NET Framework classes having a common .NET programming interface

6. Generalities • HTML controls and Web controls can sometimes to do the same thing • HTML controls can be used to conditionally create client-side script • Web controls generally provide a ‘richer’ programmatic interface • We will focus on Web controls in this lecture

7. HTML Controls (Overview) • HTML controls are similar to ordinary HTML controls • However, with the runat=“server” attribute added • ASP.NET adds a programmatic way to interact with the control instances on the server • ASP.NET controls are part of the System.Web.UI.HtmlControls namespace

8. HTML Controls (Interface) • All HTML controls inherit from the HtmlControl class • The properties are simple • Attributes returns a collection of attribute / key value pairs • Style gets a CSS collection of applied CSS properties • Disabled indicates whether the control is disabled

9. HTML Controls (Categories) • Figure 6-2 on page 239 shows the control categories • HtmlInputControl – These represent the variations of the <input> tag • HtmlContainerControl – These are Tables and other controls that contain other controls • Other – Other controls such as <img> <a>

10. HTML Controls <a> • The HTMLAnchorclass implements <a> tags • <a> tags designated runat=“server” and having an id will be seen by the server <a id="BusinessNews" runat="server"></a>

11. HTML Controls <a> • The href property contains the link • Store the text in InnerHtml or InnerText BusinessNews.HRef= "http://bloomberg.com"; BusinessNews.Title = Business news channel"; BusinessNews.InnerHtml = "<b>BusinessNews</b>";

12. HTML Input Controls • All input controls derive from HtmlInputControl • Name is the read-only property containing the control name • Type property mirrors the Type attribute • Value contains text appearing in the control instance

13. The ServerChange event • It fires for most HTML controls to denote that the control’s contents have changed from one postback to the next • Use for check boxes, radio buttons, text boxes, etc.

14. ASP.NET Server Controls • These are unique to ASP.NET • All are contained in the System.Web.UI.WebControls namespace • All derive from WebControl • runat=“server” attribute is required or the markup will be rendered verbatim • They are not the same as HTML controls • The programming interface is more intuitive

15. ASP.NET Server Controls (Properties 1) • ID – Name that will be used to reference the control instance programmatically (It’s the Name property that you are used to in VB) • Page – Page object on which the control resides • Parent – parent control instance • Use for container controls • Visible – Make the control instance visible or invisible • EnableViewState defines whether contents are persisted through view state

16. ASP.Net Server Controls (Properties 2) • The Style property contains references to a collection of CSS style MyControl.Style[“border-color”] = blue; • The CssClass property contains the name of a defined CSS class • txtStyleDemo1.CssClass = "TextBox"

17. ASP.NET Server Controls(Methods) • Focus – sets input focus to the control instance when it is rendered • HasControls – denotes whether this control instance has child controls • Controls – a collection of child controls • DataBind – binds the control instance to a data source

18. ASP.NET Server Controls (Events) • Same page and control events discussed in the previous chapter • Init – First step in the life cycle • Load – occurs when the control is loaded into the page • PreRender – fires just before the page is rendered • Unload – control has been rendered. Use only to close files or release connections

19. Other Control Characteristics • Adaptive rendering allows controls to render differently based on the browser • Control properties can be declared for different browsers, as follows: <asp:TextBox ID="TextBox4" runat="server" ie:text="IE Button" mozilla:text="Firefox button"></asp:TextBox>

20. Control State (Introduction) • State information must often be persisted across page requests • Control state is like view state • You generally don’t mess with the control state

21. Help Pages (Note)

22. Core Web Controls (Introduction) • Editable controls include check boxes, radio buttons, text boxes, labels, etc… • There is an ASP Table control that implements a table container • TableCell and TableRow implement cells and rows • See Demo • HyperLink and LinkButton implement links • Use the FileUpload control to upload files

23. ButtonControls (Introduction) • CausesValidation determines whether a validation is performed when the button is clicked. ValidationGroup also controls validation • More next time • Text contains the text that appears in the button • Visible property displays or hides the button

24. Basic Controls • The TextBox and Label controls are similar to their desktop equivalents • Check boxes operate similarly too • You will notice that there is no scroll bar

25. List Controls • Many controls work with lists • They all work similarly • ListBox • DropDownList • CheckListBox • RadioButtonList

26. The ListBox Control • Like the desktop equivalent, SelectedIndexChanged fires when an item is selected • Each item in the ListBox is a ListItem • These can be added at design time or at run time • Set AutoPostBack, as necessary

27. The ListBox Control • Properties • SelectedIndex – 0-based index of the item selected • SelectedItem – Text of the selected item • SelectedValue – An associated value (used with data binding • Set SelectionMode to allow selection of multiple items

28. Container Controls • They are used to group other controls • Make the sub controls visible • Perform similar actions to all controls in the group • Panel groups child controls • MultiView acts as a container for View controls • There are others

29. The Panel Control • Simply put, it groups other controls • Use it to • Organize controls visually • Make groups of controls visible or invisible • Create scrollable regions

30. The Panel Control • Set the ScrollBars property to enable/disable scrollbars • Set the Visible property to hide or make visible the control

31. The View and MultiView Controls • Use these to create multiple views of information • Works something like a wizard • Create one MultiView control • Create many View controls inside of the MultiView • For each View control create a button and set the CommandName and CommandArgument properties

32. Radio Buttons • They work like their desktop equivalents • Put in a RadioButtonListto create button groups • SelectedIndex contains the index of the selected button • The value is -1 if nothing is selected