asp.net session 13
TRANSCRIPT
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7/30/2019 ASP.net Session 13
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Developing Web Applications Using ASP.NET
In this session, you will learn to:
Handle and log errors
Debug Web applications
Implement Web parts in a Web application
Objectives
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Developing Web Applications Using ASP.NET
It is possible that certain unexpected errors occur in a Web
application while it is running in a real-world environment.
It would be easy to resolve such errors if a log of these
errors is maintained.
ASP.NET enables you to log unhandled errors in an eventlog, database, or some other file.
To log errors occurring in an application, you need to create
a log for the application in the event log.
Whenever an unhandled error occurs in a Web application,
the Application_Error event handler written in theGlobal.asax file is executed.
Logging Errors
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A log can be created by using the EventLog class of the
.NET Framework.
The following table describes the various properties of theEventLog class.
Logging Errors (Contd.)
Proper ty Descr ipt ionEntries Used to retrieve the contents from an event log.
Log Used to specify the name of the log from where the log information is to
be read or written.
Source Used to specify the name by which the application needs to be
registered in the event log. The name specified as the Source property
should be unique in an event log. A single event log can contain content
from multiple sources.
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The following table describes the various methods of theEventLog class:
Logging Errors (Contd.)
Method Descr ipt ion
Exists Used to determine whether the log to which the information is to be
written or read exists on the specified computer. If the computer is not
specified, the existence of the log is checked on the local computer.
SourceExists Used to determine whether a particular source name already exists on
the specified computer. If the computer is not specified, the existence of
the event source is checked on the local computer.
CreateEventSourc
e
Used to establish an application as a valid event source for adding
information to a log.
WriteEntry Used to write information to an event log.
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Problem Statement:
When a user clicks the Add New Album Details button on the
AddAlbumDetails page, the application throws a default error.
As a developer, you need to ensure that a custom error page
is displayed whenever an error occurs on the
AddAlbumDetails page. In addition to displaying the customerror page, you need to log the error in a log file.
Activity 8.1: Implementing Page-Level Error Handling
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Solution:
To display a custom error page and to log the error in a log
file, you need to perform the following steps:
1. Modify the Global.asax file.
2. Add a new Web page.
3. Design the new Web page.
4. Modify the web.config file.
5. Modify the AddAlbumDetails.aspx file
6. Execute the application.
7. Verify the logged error.
Activity 8.1: Implementing Page-Level Error Handling(Contd.)
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Developing Web Applications Using ASP.NET
Debugging is the process of finding and fixing errors in an
application.
An application may contain syntax errors, logical errors, and
run-time errors. The syntax errors are resolved during the
compilation of the Web application.The logical errors and run-time errors cannot be caught
during compilation. Such errors require you to debug the
code while it is running.
Debugging Web Applications
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There are various tools available that help you debug your
Web application.
One such tool is Visual Debugger available in Visual Studio
IDE.
The debugging tools enable you to step line-by-line throughthe statements in an application to ensure that the execution
path and the data are correct.
Debugging Web Applications (Contd.)
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To enable debugging in your ASP.NET Web application, you
must configure the application to compile into a debug build.
You can configure a Web application to compile into a
debug build by setting the debug attribute in the
element of the web.config file to
true, as
shown in the following code snippet:
Configuring Web Applications for Debugging
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You can attach a debugger to client-side scripts.
Client-side debugging works only with Internet Explorer.
Debugging Client-Side Scripts
Let us see how to debug client-side scripts
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A Web part:
Is a modular unit that can contain any type of Web-based
information, which could be a picture, static text, or database
information.
Enables a user to create a personalized user interface and
enables you to present information in a better way.
Enables you make your websites interactive.
Implementing Web Parts in a Web Application
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The advantages of using Web parts in a website are:
Web parts enable users to personalize the content of a Web
page.
Web parts can be assigned role-based access, thereby,
determining which Web part can be shared by all users or
which should be hidden for certain roles.
Web parts can be connected to each other. One of the
connected Web parts is defined as a provider and the other as
a consumer.
Advantages of Using Web Parts
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Personalization is one of the main advantages of using Web
parts.
You can implement personalization by allowing a user to
view a Web page in several display modes.
Display modes allow users to modify or personalize theWeb page.
The different types of display modes available are:
Browse
Edit
DesignCatalog
Connect
Web Part Modes
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ASP.NET provides you with the Web parts control set that is
designed to implement Web parts in your websites.
Some of the Web part controls available in ASP.NET are
described in the following table.
Web Parts Control Set
Property Descript ion
WebPartManager Manages all the Web part controls on a page. Each Web
part page contains exactly one WebPartManager control.
CatalogZone Contains CatalogPart controls and is used to create a
catalog of Web part controls from which a user can select
a Web part control to add to a page.
EditorZone Contains EditorPart controls and is used to enable a user
to edit and personalize Web part controls on a page.
WebPartZone Contains the overall layout for the Web Part controls that
compose the main user interface of a page.ConnectionsZone Contains Connection controls.
CatalogPart Contains a list of available Web part controls that a user
can add to a page.
Connection Creates a connection between two Web part controls on a
page.
EditorPart Serves as the base class for specialized controls that
provide the functionality to edit Web parts.
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Once you have created a Web part page, you can allow
users to switch between the various Web part display
modes.
To enable a user to switch between the various modes, you
can include a drop-down list on the Web page that allows a
user to select the desired mode.
Web Parts Control Set (Contd.)
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You can then type the following code snippet in the
SelectedIndexChanged event of the DropDownList control:WebPartManager wpm =
WebPartManager.GetCurrentWebPartManager(Page);
string selectedMode = DropDownList1.SelectedValue;
WebPartDisplayMode mode =
wpm.SupportedDisplayModes[selectedMode];
if (mode != null)
{
wpm.DisplayMode = mode;
}
Web Parts Control Set (Contd.)
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Problem Statement:
The management of MusicMania wants its website to provide a
customizable user interface to all its users. The users should be
able to hide, show, and arrange the components on the home
page according to their requirements.
As the first step towards implementing this requirement, youneed to create a Web parts page, Portal.aspx. The Portal.aspx
page should include a Web part that displays the availability
status of the MusicMania database.
Prerequisite: Ask your faculty to provide you the required
starter files.
Activity 9.1: Creating a Web Parts Page
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Solution:
To create the Web parts page, you need to perform the
following tasks:
1. Create a user control.
2. Add a new Web page.
3. Design the new Web page.
4. Test the application.
Activity 9.1: Creating Web Parts Page(Contd.)
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There are situations where you need to connect sets of data
from different data sources.
Web part connections are based on a pull model, where the
consumer pulls data from the provider.
To create a connection, the provider control defines acommunication contract in the form of an interface, indicating
the data it can provide.
The consumer control knows about this contract and retrieves
the data through the connection.
Connecting Web Parts
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To participate in a connection, a Web part needs to define a
connection point.
Connection points are of two types:
Provider connection points
Consumer connection points
Connecting Web Parts (Contd.)
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To create connected Web parts, you need to perform the
following tasks:
1. Create the provider Web part as a custom control.
2. Create the consumer Web part as a custom control
3. Add the Web parts to the Toolbox.
4. Add the Web part controls from the Toolbox to a Web part page
and assign an ID and title to each of the two controls.
5. Add the connection information to the WebPartManager control
by opening the Web part page in the Source view and adding a element inside the
element.
Connecting Web Parts (Contd.)
Let us see how to create and use a Web user control
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Developing Web Applications Using ASP.NET
In this session, you learned that:
ASP.NET enables you to log unhandled errors in an event log,
database, or some other file.
An event log can be created by using the EventLog class of the
.NET Framework.
Debugging is the process of finding and fixing errors in an
application.
There are various tools available that help you debug your
Web application. One such tool is Visual Debugger available in
Visual Studio IDE.
The features of a debugger that help you debug Webapplications are:
Breakpoints
Stepping
Data Viewing
Summary
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Developing Web Applications Using ASP.NET
The aspnet_wp.exe process is attached to the debugger to
debug a running page.
A Web part is a modular unit that can contain any type of Web-
based information.
The advantages of using Web parts in a website are:
Web parts enable users to personalize the content of a Webpage.
Web parts can be assigned role-based access, thereby
determining which Web parts can be shared by all users or which
should be hidden for certain roles.
Web parts can be connected to each other.
The different types of display modes of a Web part are:
Browse mode
Edit mode
Design mode
Catalog mode
Connect mode
Summary (Contd.)
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A Web page that is composed of Web parts is known as a Web
part page.
A Web part page is divided into zones that provide the
structure for placing Web parts.
Summary (Contd.)