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)

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 tag HtmlContainerControl – These are Tables and other controls that contain other controls Other – Other controls such as

Slide 10 HTML Controls The HTMLAnchor class implements tags tags designated runat=“server” and having an id will be seen by the server

Slide 11 HTML Controls The href property contains the link Store the text in InnerHtml or InnerText BusinessNews.HRef= " BusinessNews.Title = Business news channel"; BusinessNews.InnerHtml = " BusinessNews ";

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 style MyControl.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:

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