asp.net session 04

7/30/2019 ASP.net Session 04

1/30

Slide 1 of 30Ver. 1.0

Developing Web Applications Using ASP.NET

In this session, you will learn to:

Create custom controls

Work with styles

Work with themes

Objectives


2/30



Developers use various Web server controls to enable users

to interact with Web pages.

There might be a situation where:

You need some functionality that is not provided by the

in-built Web server controls.You might want to reuse the same set of controls, which you

have added to one Web page, on another Web page.

In such situtaions, you can create a custom control with the

required customizations and then reuse it in as many Web

applications as you want.

Creating Custom Controls


3/30



You can create the following types of custom controls:

Web user controls

Web custom controls

Templated user controls

Creating Custom Controls (Contd.)


4/30



Web user controls:

Are containers that can be created by combining one or more

Web server controls.

Are similar to ASP.NET Web pages in the context that they

contain both a user interface page and code.

Various characteristics of a Web user control are:

The file name extension of a user control is .ascx.

It contains the @Control directive instead of the @Page

directive.

It cannot run as a stand-alone file. It needs to be added to an

ASP.NET page to make it work.

It does not contain an , , or element.

These elements must be present on the Web page that is

hosting these controls.

Web User Controls


5/30



A Web user control on a Web page must be registered

before it is used.

You can register a Web user control by using the

@ Register directive, as shown in the following code

snippet:

The preceding code snippet contains the following three

attributes:

TagPrefix

TagName

Src

Web User Controls (Contd.)

Let us see how to create and use a Web user control


6/30



Web custom controls:

Provide an approach to reuse logic in an ASP.NET application.

Are written as classes.

Are written entirely by using managed code and have no

markup files.

Are compiled into an assembly before the deployment of the

application.

Web Custom Controls


7/30Slide 7 of 30Ver. 1.0


Web custom controls are of the following three types:

Controls that combine two or more existing controls

Controls that extend the functionality of an existing control

Controls that are not similar to any existing control

Web Custom Controls (Contd.)

Let us see how to create and use a composite control

Let us see how to create and use a Web custom control

that extends the functionality of an existing control

Let us see how to create and use a Web custom

control that is not similar to any existing control




A templated user control:

Allows developers to modify the layout of its user interface by

defining their own templates.

Allows the separation of control data from its presentation.

Does not have a user interface. Instead, it simply implements

a naming container and includes a class whose properties and

methods are accessible to the host page.

Templated User Controls




To create a templated user control, you need to perform the

following steps:

1. Add an ASP.NET PlaceHolder control in the .ascx file of the

user control to specify the place where you want the template

to appear.

2. Implement a property of type ITemplate in the code of the

user control.

3. Define a server control class that implements theINamingContainer interface as a container in which an

instance of the template can be created.

4. Apply the TemplateContainer attribute to the property thatimplements ITemplateand pass the type of the templates

naming container as the argument to the attributes

constructor.

Templated User Controls (Contd.)


10/30Slide 10 of 30Ver. 1.0


5. For each data item, write code in the Page_Init event

handler of the user control to:

a. Create an instance of the naming container class.

b. Create an instance of the template in the naming container.

c. Add the naming container instance to the Controls property of

the PlaceHolder server control.

Templated User Controls (Contd.)

Let us see how to create and use a templated user control


11/30Slide 11 of 30Ver. 1.0


The look and feel of a Web page depends upon the

appearance and arrangement of the HTML elements

contained in it.

Therefore, you need to format the HTML elements

contained in your Web page to make it look attractive.

Styles enable a programmer to apply consistent formatting

across the entire website.

Styles are used to define a set of formatting options, which

can be reused to format different HTML elements on a

single or multiple Web pages.

Working with Styles


12/30Slide 12 of 30Ver. 1.0


You can define styles in any of the following ways:

Using inline styles

Using an embedded style sheet

Using an external (linked) style sheet

Working with Styles (Contd.)


13/30Slide 13 of 30Ver. 1.0


Inline styles:

Are style definitions that are applied to the style property of a

particular HTML element.

Are placed directly inside the element on which it has to be

implemented.

Are used when you want to apply one-time formatting to an

HTML element.

To use inline styles in a Web page, you need to use the

style attribute in the relevant HTML tag.

Using Inline Styles


14/30Slide 14 of 30Ver. 1.0


An embedded style sheet is a group of styles that aredefined by using the tag.

The tag needs to be placed within the

tag on your Web page.

The embedded style sheet:Is used when you want to apply a unique style to the various

elements on a Web page.

Enables you to define all the styles for a Web page at one

place, which reduces the time required to design a Web page.

Using an Embedded Style Sheet


15/30Slide 15 of 30Ver. 1.0


The style definitions in an external style sheet are stored in

a separate file having the .css extension.

An external style sheet is used when you want to apply the

same style rules to more than one Web page on a website.

The external style sheet can contain styles for individualelements or generic styles that can be applied to any

element.

Using an External (Linked) Style Sheet

Let us see how to create styles by using style builder

Let us see how to modify a style rule by using the CSSproperties window

Let us see how to create a Style Sheet


16/30Slide 16 of 30Ver. 1.0


ASP.NET themes:

Are a collection of properties that enable you to define the

appearance of Web pages and controls on your website.

Can include skin files, cascading style sheet files (.css files),

and graphics.

Give your Web pages a consistent appearance across the

website.

Working with Themes


17/30Slide 17 of 30Ver. 1.0


You can use a theme in Web applications by creating a skin

file and attaching them to the Web pages on which you want

to apply the theme.

Skin files are:

Used to define the property settings for ASP.NET Web servercontrols.

Created and stored in a theme folder, which is placed inside

the folder named App_Themes. The App_Themes folder is

placed inside the top-level directory of your Web application.

Creating a Theme


18/30Slide 18 of 30Ver. 1.0


You can define multiple themes for your Web application,

but can apply only one theme on a given page at a time.

You can create multiple skin files in a theme directory or

place all the control tags in a single skin file.

Creating a Theme (Contd.)

Let us see how to create a theme


19/30Slide 19 of 30Ver. 1.0


You can apply a theme either to a particular Web page or to

all the Web pages on a website.

If a theme is applied to a particular Web page, the theme

settings are applied only to that Web page.

If you apply the theme to the entire website, the themesettings are applied to all the Web pages on the website.

Applying a Theme


20/30Slide 20 of 30Ver. 1.0


Applying a theme to a Web page:

To apply a theme to a particular Web page, you need to bind

the theme at the page level.

If you bind the theme at the page level, the styles and skins are

only applied to that Web page and its controls.

To bind a theme at the page level, you need to set the Themeattribute of the @ Page directive.

For example, the following @ Page directive specifies that the

theme, SkinFile, is applied to the Web page:

Applying a Theme (Contd.)


21/30Slide 21 of 30Ver. 1.0


If you have defined settings for the control locally as well as in

the theme, the settings defined in the theme override the local

control settings, thus, maintaining a consistent look.

However, if you have used a stylesheet theme, then the local

page settings override the settings defined in the stylesheet

theme.You can use stylesheet theme if you want the theme to be

applied only to those controls whose settings have not

explicitly been defined at the page level.



22/30Slide 22 of 30Ver. 1.0


If you do not want the theme property to be applied to aparticular control, you can set the EnableTheming property of

that control on the Web page to false, as shown in the

following code snippet:



23/30



In addition to applying a theme at the design time, you can apply

a theme dynamically.

To apply a theme dynamically, you need to set the Page.Theme

orPage.StyleSheetTheme property in the Page_PreInit

event in your code.

For example, you have created a skin file, SkinFile.skin, in theSkinFile folder. To set this theme dynamically, you need to write

the following code snippet:

protected void Page_PreInit(object sender,EventArgs e)

{

Page.Theme = "MyTheme"; //name of the folder in

//which you have stored the

//skin file.

}



24/30



Applying a theme to a website:

To apply the theme to all the Web pages on a website, you

need to bind the theme at the website level.

If you bind the theme at the website level, the styles and skins

are applied to all the Web pages and controls on the website

unless you override a theme for an individual Web page.



25/30



To apply a theme to the entire website, you need to configurethe element in the web.config file, as shown in the

following code snippet:

...



26/30



Skin files standardize the look and feel of controls across all

the Web pages on a website.

There may be situations where you want multiple occurrences

of a control to appear differently on the same Web page.

ASP.NET allows you to create multiple settings for the samecontrol by using multiple skins.

Creating Multiple Skins


27/30



When you create more than one theme for the same control,

ASP.NET generates an error stating that a control can have a

single default skin.

The error can be avoided by using a named skin.

A named skin can be created by supplying the SkinIDattribute.

Creating Multiple Skins (Contd.)


28/30



The following code snippet can be used to create multiple

skins for a button control:

Creating Multiple Skins (Contd.)


29/30



In this session, you learned that:

The three types of custom controls are:

Web user controls

Web custom controls

Templated user controls

Styles are used to define a set of formatting options that can

be reused on a single or multiple Web pages.

Styles can be defined in any of the following ways:

Using inline styles

Using an embedded style sheet

Using an external (linked) style sheetInline styles are style definitions that are applied to the style

property of a particular HTML element.

An embedded style sheet is a group of styles that are definedby using the tag.

Summary


30/30


The style definitions in an external style sheet are stored in a

separate file having the .css extension.

ASP.NET themes are a collection of properties that enable you

to define the appearance of Web pages and controls on your

website.

You can apply a theme either to a particular Web page or to allthe Web pages on a website.

To bind a theme at the page level, you need to set the Theme

attribute of the @ Page directive.

To apply a theme to the entire website, you need to configurethe element in the web.config file.

You can create more than one theme for the same control.

Summary (Contd.)

asp.net session 04

Documents