ASP.net Session 08

7/30/2019 ASP.net Session 08

1/33

Slide 1 of 33Ver. 1.0

Developing Web Applications Using ASP.NET

In this session, you will learn to:

Implement server-side state management

Manage state by using cross-page posting

Implement caching

Identify basics of data access in Web applicationsAccess data by using the presentation layer

Objectives


2/33



ASP.NET provides the profiles feature to implement

personalization in Web applications.

This enables developers to store preferences without writing

much code. These preferences are stored as named

properties in profiles.The properties that need to be stored in each user profile for

an application can be configured in the web.config file, as

shown in the following example:

Profile Properties


3/33



After configuring the profile properties in the web.config file,you can access them by using the Profile object.

The value of the profile property can be set, as shown in the

following code snippet:

Profile.UserName = TextBox1.Text;The value of profile property can be retrieved, as shown in

the following code snippet:

TextBox1.Text = Profile.UserName;

By default, the profile properties are stored in the aspnetdb

database.

Profile Properties (Contd.)

Let us see how to create the aspnetdb database.


4/33



By default, a Button control on a Web page submits the

page back to itself.

Sometimes, you may want to post one page to another.

In such a case, you can set the PostBackUrl property of

the Button control to the URL of the target page.This posting of information from one page to another page is

called cross-page posting.

Managing State by Using Cross-Page Posting


5/33



The Page class exposes a public property named

PreviousPage.

If the source and target pages are in the same application,the PreviousPage property contains a reference to the

source page.You can access the values in the controls on the sourcepage by using the FindControl method.

You can check whether a page is running as a result of apostback by using the IsPostBack property of the Page

class.You can check whether a page is running as a result of across-page postback by using the IsCrossPagePostBack

property of the Page class.

Managing State by Using Cross-Page Posting (Contd.)


6/33



Problem Statement:

The management at MusicMania wants to allow the users to

place orders for music CDs online. For this, a user needs to

register on the website before placing the order. The

registration process requires the user to fill a form, which

contains user-specific information. After filling the form, theuser needs to click the Submit button. After the registration is

successful, a new Web page should appear that displays the

message "Welcome , you have successfully

registered."

You have been asked by the team leader to implement this

functionality on the MusicMania website.

Activity 5.3: Managing State by Using Cross-Page Posting


7/33Slide 7 of 33Ver. 1.0


Solution:

To display the user name on another Web page by using

cross-page posting, you need to perform the following tasks:

1. Add a new Web page.

2. Design the Web page.

3. Modify the Home page.

4. Add a new Web page.

5. Design the Web page.

6. Verify the application.

Activity 5.3: Managing State by Using Cross-Page Posting (Contd.)




Speed is a critical factor that judges the success or failure of

any website.

When multiple users access a website simultaneously, slow

access to Web pages is a common problem that arises.

The problem of slow access can be solved by using atechnique called caching.

Caching:

Improves the performance of any Web application by

temporarily storing frequently used Web objects, such as

HTML pages, on local hard disks for later retrieval.Enables you to improve the performance of Web applications.

Implementing Caching




The major benefits of using Web caching are:

Reduced access time

Less bandwidth required

Less load on server

ASP.NET supports three types of caching:Output Caching

Fragment Caching

Data Caching

Implementing Caching (Contd.)


10/33Slide 10 of 33Ver. 1.0


Output caching:

Improves the performance of an ASP.NET application by

caching the rendered markup of an ASP.NET Web page.

Is useful when the content of the Web page changes rarely.

To implement output caching, you need to insert the@ OutputCache directive, as shown in the following

example:

Output Caching


11/33Slide 11 of 33Ver. 1.0


In fragment caching, the data from some specific sections of

the page can be cached.

It is also referred to as partial page caching.

To implement fragment caching, the portion of the page that

is to be cached is encapsulated in a user control, and thenthe @ OutputCache directive is added to the control, as

shown in the following example:

Fragment Caching


12/33Slide 12 of 33Ver. 1.0


Data caching is used to store frequently used data in thebuilt-in collection object called Cache.

It is a property of the Page class, and it returns an instance

of the System.Web.Caching.Cache class.

The Cache object:Works like the Application object.

Is globally available to all requests from all clients in the

application.

Differs from the Application object in the following ways:

TheCache

object does not need to be explicitly locked or

unlocked.

Items in the Cache object are removed automatically.

Items in the Cache object can be linked to a file, a database

table, or another type of resource.

Data Caching


13/33Slide 13 of 33Ver. 1.0


You can store a variable by the name, uname, in the Cache

object, and assign it a value, as shown in the following code

snippet:

Cache ["uname"] = "Robert";

You can retrieve the value from the Cache object, as shownin the following code snippet:TextBox1.Text = Cache["uname"];

Data Caching (Contd.)


14/33Slide 14 of 33Ver. 1.0


Most Web applications are designed by using the multiple

tier model known as the N-tier model.

The following figure shows a basic N-tier model.

Identifying the Basics of Data Access in Web Applications

DATA ACCESS LAYER

BUSINESS RULES LAYER

PRESENTATION LAYER


15/33Slide 15 of 33Ver. 1.0


The presentation layer, in a Web application, is the interface

that appears when a user opens a Web page in the browser.

If you see the source code of the page, you would only see

the code such as HTML, Javascript, and Cascading Style

Sheets.

You would not be able to see the database queries, loops,

calls to classes, or any behind-the-scenes processing.

The presentation layer does not contain any data access

code or program logic.

In case of small Web applications, you may find the databaseaccess layer merged with the presentation layer.

Presentation Layer


16/33Slide 16 of 33Ver. 1.0


The business rules layer:

Is also known as the business logic tier or the application tier.

Contains all the classes and the source code of the Web

application.

Allows you to separate the application logic from the user

interface of a Web page.

Enables the programmer to easily search for a specific code

because the code is not cluttered with HTML or Javascript.

Does not contain HTML or JavaScript code.

Business Rules Layer


17/33Slide 17 of 33Ver. 1.0


You can implement the data access logic in the presentation

layer; however this is not recommended because:

It clutters the data access code with the HTML and Javascript

code.

It tightly couples the data access logic with the presentation

layer. This prevents the data access logic to be reused in other

Web applications.

All the preceding limitations can be overcome by separating

the data access logic from the presentation layer.

It can be done by creating a new layer and implementing the

data access logic in it.

This separate layer is known as DAL, which is typically

implemented as a separate class library.

Database Access Layer


18/33Slide 18 of 33Ver. 1.0


Most of the modern day Web applications need to manipulate

data in databases. This can be done by implementing data

access logic in applications.

If the data access logic is not to be reused in any other

application, then the logic can be implemented in the

presentation layer (ASP.NET pages). This can be done by

using:

Data source controls

ADO.NET

Accessing Data by Using the Presentation Layer


19/33Slide 19 of 33Ver. 1.0


Data source controls:

Allow you to work with different types of data sources such as a

database, an XML file, or a middle-tier business object.

Act as a bridge between the application and the data sources.

Can connect to the data sources and retrieve data without

requiring you to write any code.

Do not provide the interface to display data. To display the

retrieved data, it is made available to the data controls or data-

aware controls.

Data Source Controls


20/33Slide 20 of 33Ver. 1.0


Data source controls perform the following tasks:

Retrieve data from a data source and supply it to the data

controls or data aware controls.

Update the data source when edits take place.

Data source controls in ASP.NET:

SqlDataSource

AccessDataSource

ObjectDataSource

XmlDataSource

SiteMapDataSourceLinqDataSource

Data Source Controls (Contd.)


21/33Slide 21 of 33Ver. 1.0


The SqlDataSource control:

Is used to access data from an SQL relational database.

Can be used to access any database product for which there is

a managed ADO.NET provider.

Is used in conjunction with data controls.

The following table lists some properties of the

SqlDataSource control.


Proper ty Descr ipt ion

ProviderName Gets or sets the name of the . provider that is used to

connect to an underlying data source.ConnectionString Gets or sets the connection string that is used to

connect to an underlying data source.SelectCommand Gets or sets the SQL string that is used to retrieve

data from the underlying data source.DeleteCommand Gets or sets the SQL string that is used to delete data

from the underlying data source.InsertCommand Gets or sets the SQL string that is used to insert data

in the underlying data source.UpdateCommand Gets or sets the SQL string that is used to update data

in the underlying data source.


22/33Slide 22 of 33Ver. 1.0


The AccessDataSource control:

Works with Microsoft Access databases.

Uses SQL queries to perform data retrieval.

Cannot be used to access Access databases that are protected

by a user name or password.


AccessDataSource control.



ProviderName Gets or sets the name of the . provider that is used to

connect to a Microsoft Access.DataFile Gets or sets the location of the Microsoft Access file.

SelectCommand Gets or sets the SQL string that is used to retrieve

data from the underlying data source.DeleteCommand Gets or sets the SQL string that is used to delete

data from the underlying data source.InsertCommand Gets or sets the SQL string that is used to insert data

in the underlying data source.UpdateCommand Gets or sets the SQL string that is used to update

data in the underlying data source.


23/33



The ObjectDataSource control:

Represents a middle-tier object that enables developers to

access data from business objects.


ObjectDataSource control.


Property Descript ion

TypeName Identifies the name of the class that the ObjectDataSource works

with.SelectMethod Gets or sets the method or function that is invoked to retrieve

data.SelectParameters Gets the parameters collection that contains the parameters used

by the SelectMethodproperty.

InsertMethod Gets or sets the method or function that is invoked to insert data.

InsertParameters Gets the parameters collection that contains the parameters usedby the InsertMethodproperty.

UpdateMethod Gets or sets the method or function that is invoked to update data.

UpdateParameters Gets the parameters collection that contains the parameters usedby the UpdateMethodproperty.

DeleteMethod Gets or sets the method or function that is invoked to delete data.

DeleteParameters Gets the parameters collection that contains the parameters usedby the DeleteMethodproperty.


24/33



The XmlDataSource control:

Presents XML data to data-bound controls.

Can be used by data-bound controls to display hierarchical as

well as tabular data.

Loads data from an XML file that is specified by the DataFile

property.

Can also store XML data in string form by using the Data

property.


XmlDataSource control.



DataFile Specifies the filename of the XML file that is to be

bound with the XmlDataSource control.Data Gets or sets the block of xml data that is to be bound

with the XmlDataSource control in string form.


25/33



The SiteMapDataSource control:

Provides navigation data to the navigational controls.

Enables Web server controls that are not specifically site

navigation controls, such as the TreeView and Menu controls, to

bind to site map data.

Can be bound to the navigational controls by using the

DataSourceID property of the navigational controls.


SiteMapDataSource control.



SiteMapProvider Gets or sets the name of the site map provider.

StartingUrlNode Used to set the URL in the sitemap that will be

considered as the root node.ShowStartingNode Indicates whether to show starting node or not. It can

have two values, True orFalse.


26/33



Data-bound Web server controls:

Can be bound to a data source control to display and modify

data in a Web application.

Are composite controls that combine other Web controls, such

as Label and TextBox controls into a single unit.

Enable you to customize the layout of the control using

templates.

Displaying Data in Data-Bound Web Server Controls


27/33



ASP.NET provides following data-bound Web server controls:

GridView control

DetailsView control

FormView control

ListView controlDataList control

Repeater control

DataPager control

Let us see how to retrieve data from a data source by usingthe SqlDataSource control

Displaying Data in Data-Bound Web Server Controls (Contd.)


28/33



Binding controls to data by using data binding syntax:

Data binding is a technique of linking data and user interface

objects.

Using data binding, you can bind data in a data source to a user

interface object.

On the basis of the number of bound values that can be

displayed through a user interface object, binding can be

classified into:

Single-value data binding

Repeated-value data binding

Binding Controls to Data by Using Data Binding Syntax


29/33



Single-value data binding:

Single-value data binding involves binding the controls that can

display one data value at a time to a data source.

Single-value controls do not support any data bindingproperties, such as the DataSource property or the

DataMember property.

Binding Controls to Data by Using Data Binding Syntax (Contd.)


30/33



Consider a case where you need to bind a Label control to a

public variable that displays the current date and time. For this,

you can write the following code in the .aspx.cs file:

public partial class _Default : System.Web.UI.Page

{

public string dt = DateTime.Now.ToString();

protected void Page_Load(object sender, EventArgs e)

{

this.DataBind();/*binds the data source to the

invoked server control and all its child

controls*/}

}



31/33



Repeated-value data binding:

Repeated-value data binding involves binding server controls to

structures, such as ArrayList and DataView objects, whichimplement the IEnumerable interface.

The following example shows how you can bind an ArrayList to

a ListBox control:

protected void Page_Load(object sender, EventArgs e)

{

ArrayList Month = new ArrayList();

Month.Add("Jan");

Month.Add("Feb");Month.Add("Mar");

Month.Add("Apr");

ListBox1.DataSource = Month;

ListBox1.DataBind();

}



32/33



In this session, you learned that:

The profiles feature is used to implement personalization in

Web applications.

Caching improves the performance of a Web application by

temporarily storing frequently used Web objects on local hard

disks for later retrieval.

ASP.NET supports three types of caching:

Output Caching

Fragment Caching

Data Caching

The basic N-tier model consists of the following layers:Presentation Layer

Business Rules Layer

Database Access Layer

Summary


33/33


You can implement data access logic in the presentation layer

(ASP.NET pages) by using:

Data source controls

ADO.NET

Summary (Contd.)

ASP.net Session 08

Documents

Transcript of ASP.net Session 08