Asp.NET Core Server Controls

Slide 2

Lecture Overview Understanding the types of ASP.NET

controls HTML controls ASP.NET (Web) controls

Slide 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>

Slide 4

Categorizing Server Controls

ASP.NET CONTROLS

HTML CONTROLS

WEB CONTROLS

Slide 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

Slide 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

Slide 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

Slide 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

Slide 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>

Slide 10

HTML Controls <a> The HTMLAnchor class implements <a>

tags <a> tags designated runat=“server”

and having an id will be seen by the server

<a id="BusinessNews" runat="server"></a>

Slide 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>";

Slide 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

Slide 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.

Slide 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

Slide 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

Slide 16

ASP.Net Server Controls (Properties 2) The Style property contains references

to a collection of CSS styleMyControl.Style[“border-color”] = blue;

The CssClass property contains the name of a defined CSS class

txtStyleDemo1.CssClass = "TextBox"

Slide 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

Slide 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

Slide 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>

Slide 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

Slide 21

Help Pages (Note)

Slide 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

Slide 23

Button Controls (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

Slide 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

Slide 25

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

Slide 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

Slide 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

Slide 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

Slide 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

Slide 30

The Panel Control Set the ScrollBars property to

enable/disable scrollbars Set the Visible property to hide or

make visible the control

Slide 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

Slide 32

Radio Buttons They work like their desktop equivalents Put in a RadioButtonList to create

button groups SelectedIndex contains the index of the

selected button The value is -1 if nothing is selected