Asp.net Q/A Part 2

on 10:07 AM



What is the difference between “Web.config” and “Machine.Config” ?
“Web.config” files apply settings to each web application, while “Machine.config” fileapply settings to all ASP.NET applications.
What is a SESSION and APPLICATION object ?

Session object store information between HTTP requests for a particular user, while application object are global across users.

What is the difference between Server.Transfer and response.Redirect ?
Following are the major differences between them:-
√ Response.Redirect sends message to the browser saying it to move to some
different page, while server.transfer does not send any message to the browser but rather redirects the user directly from the server itself. So in server.transfer there is no round trip while response.redirect has a round trip and hence puts a load on server.
√ Using Server.Transfer you can not redirect to a different from the server itself.
Example if your server is www.yahoo.com you can use server.transfer to move
to www.microsoft.com but yes you can move to www.yahoo.com/travels, i.e. within websites. This cross server redirect is possible only using Response.redirect.
√ With server.transfer you can preserve your information. It has a parameter called as “preserveForm”. So the existing query string etc. will be able in the calling page. If you are navigating within the same website use “Server.transfer” or else go for “response.redirect()”

What is the difference between Authentication and
authorization?
This can be a tricky question. These two concepts seem altogether similar but there is wide range of difference. Authentication is verifying the identity of a user and authorization is process where we check does this identity have access rights to the system. In short we can say the following authentication is the process of obtaining some sort of credentials from the users and using those credentials to verify the user’s identity. Authorization is the process of allowing an authenticated user access to resources. Authentication always proceed to Authorization; even if your application lets anonymous users connect and use
the application, it still authenticates them as being anonymous.

What is impersonation in ASP.NET ?
By default, ASP.NET executes in the security context of a restricted user account on the local machine. Sometimes you need to access network resources such as a file on a shared drive, which requires additional permissions. One way to overcome this restriction is to use impersonation. With impersonation, ASP.NET can execute the request using the identity of the client who is making the request, or ASP.NET can impersonate a specific
account you specify in web.config.

Can you explain in brief how the ASP.NET authentication process works?
ASP.NET does not run by itself, it runs inside the process of IIS. So there are two
authentication layers which exist in ASP.NET system. First authentication happens at the IIS level and then at the ASP.NET level depending on the WEB.CONFIG file.
Below is how the whole process works:-
√ IIS first checks to make sure the incoming request comes from an IP address
that is allowed access to the domain. If not it denies the request.
√ Next IIS performs its own user authentication if it is configured to do so. By
default IIS allows anonymous access, so requests are automatically authenticated, but you can change this default on a per – application basis
with in IIS.
√ If the request is passed to ASP.net with an authenticated user, ASP.net checks
to see whether impersonation is enabled. If impersonation is enabled, ASP.net
acts as though it were the authenticated user. If not ASP.net acts with its own
configured account.
√ Finally the identity from step 3 is used to request resources from the operating
system. If ASP.net authentication can obtain all the necessary resources it
grants the users request otherwise it is denied. Resources can include much
more than just the ASP.net page itself you can also use .Net’s code access
security features to extend this authorization step to disk files, Registry keys
and other resources.
What are the various ways of authentication techniques in ASP.NET?
Selecting an authentication provider is as simple as making an entry in the web.config file for the application. You can use one of these entries to select the corresponding built in authentication provider:
√ authentication mode=”windows”
√ authentication mode=”passport”
√ authentication mode=”forms”
√ Custom authentication where you might install an ISAPI filter in IIS that
compares incoming requests to list of source IP addresses, and considers
requests to be authenticated if they come from an acceptable address. In that
case, you would set the authentication mode to none to prevent any of the .net authentication providers from being triggered.
Windows authentication and IIS
If you select windows authentication for your ASP.NET application, you also have to configure authentication within IIS. This is because IIS provides Windows authentication.IIS gives you a choice for four different authentication methods:
Anonymous,basic,digest and windows integrated If you select anonymous authentication, IIS doesn’t perform any authentication, Any one is allowed to access the ASP.NET application.If you select basic authentication, users must provide a windows username and password to connect. How ever this information is sent over the network in clear text, which makes basic authentication very much insecure over the internet.
If you select digest authentication, users must still provide a windows user name and password to connect. However the password is hashed before it is sent across the network.Digest authentication requires that all users be running Internet Explorer 5 or later and that windows accounts to stored in active directory.
If you select windows integrated authentication, passwords never cross the network.Users must still have a username and password, but the application uses either the Kerberos or challenge/response protocols authenticate the user. Windows-integrated authentication requires that all users be running internet explorer 3.01 or later Kerberos is a network authentication protocol. It is designed to provide strong authentication for client/server applications by using secret-key cryptography. Kerberos is a solution to network security
problems. It provides the tools of authentication and strong cryptography over the network to help to secure information in systems across entire enterprise
Passport authentication
Passport authentication lets you to use Microsoft’s passport service to authenticate users of your application. If your users have signed up with passport, and you configure the authentication mode of the application to the passport authentication, all authentication duties are off-loaded to the passport servers.Passport uses an encrypted cookie mechanism to indicate authenticated users. If users have already signed into passport when they visit your site, they’ll be considered authenticated by ASP.NET. Otherwise they’ll be redirected to the passport servers to log in. When they are successfully log in, they’ll be redirected back to your site.To use passport authentication you have to download the Passport Software Development
Kit (SDK) and install it on your server. The SDK can be found at http://
msdn.microsoft.com/library/default.asp?url=/downloads/list/websrvpass.aps. It includes full details of implementing passport authentication in your own applications.
Forms authentication
Forms authentication provides you with a way to handle authentication using your own custom logic with in an ASP.NET application. The following applies if you choose forms authentication.
√ When a user requests a page for the application, ASP.NET checks for the
presence of a special session cookie. If the cookie is present, ASP.NET assumes
the user is authenticated and processes the request.
√ If the cookie isn’t present, ASP.NET redirects the user to a web form you provide
You can carry out whatever authentication, it check’s you like it checks your form. When the user is authenticated, you indicate this to ASP.NET by setting a property, which creates the special cookie to handle subsequent requests.

What’s difference between Datagrid, Datalist and repeater ?
A Datagrid, Datalist and Repeater are all ASP.NET data Web controls.
They have many things in common like DataSource Property, DataBind Method
ItemDataBound and ItemCreated.When you assign the DataSource Property of a Datagrid to a DataSet then each DataRow present in the DataRow Collection of DataTable is assigned to a corresponding DataGridItem and this is same for the rest of the two controls also. But The HTML code generated for a Datagrid has an HTML TABLE element created for the particular DataRow and its a Table form representation with Columns and Rows. For a Datalist its an Array of Rows and based on the Template Selected and the RepeatColumn Property value We can specify how many DataSource records should appear per HTML row. In short in datagrid we have one record per row, but in datalist we can have five or six rows per row.For a Repeater Control, the Datarecords to be displayed depends upon the Templates specified and the only HTML generated is the due to the Templates.In addition to these, Datagrid has a in-built support for Sort, Filter and paging the Data,which is not possible when using a DataList and for a Repeater Control we would require to write an explicit code to do paging.

From performance point of view how do they rate ?

Repeater is fastest followed by Datalist and finally datagrid.

What is the method to customize columns in DataGrid?
Use the template column.

How can we format data inside DataGrid?

Use the DataFormatString property.

How to decide on the design consideration to take a Datagrid, datalist or repeater?

Many make a blind choice of choosing datagrid directly, but that's not the right way.Datagrid provides ability to allow the end-user to sort, page, and edit its data. But it comes at a cost of speed. Second the display format is simple that is in row and columns.Real life scenarios can be more demanding that With its templates, the DataList provides more control over the look and feel of the displayed data than the DataGrid. It offers better performance than datagrid Repeater control allows for complete and total control. With the Repeater, the only HTML
emitted are the values of the databinding statements in the templates along with the HTML markup specified in the templates—no "extra" HTML is emitted, as with the DataGrid and DataList. By requiring the developer to specify the complete generated HTML markup, the Repeater often requires the longest development time. But repeater does not provide editing features like datagrid so everything has to be coded by programmer.However, the Repeater does boast the best performance of the three data Web controls.Repeater is fastest followed by Datalist and finally datagrid.
Difference between ASP and ASP.NET?
ASP.NET new feature supports are as follows :-
Better Language Support
√ New ADO.NET Concepts have been implemented.
√ ASP.NET supports full language (C#, VB.NET, C++) and not simple scripting
like VBSCRIPT..
Better controls than ASP
√ ASP.NET covers large set’s of HTML controls..
√ Better Display grid like Datagrid, Repeater and datalist.Many of the display
grids have paging support.
Controls have events support
√ All ASP.NET controls support events.
√ Load, Click and Change events handled by code makes coding much simpler
and much better organized.
Compiled Code
The first request for an ASP.NET page on the server will compile the ASP.NET code and keep a cached copy in memory. The result of this is greatly increased performance.
Better Authentication Support
ASP.NET supports forms-based user authentication, including cookie management and automatic redirecting of unauthorized logins. (You can still do your custom login page and custom user checking).
User Accounts and Roles
ASP.NET allows for user accounts and roles, to give each user (with a given role) access to different server code and executables.
High Scalability
√ Much has been done with ASP.NET to provide greater scalability.
√ Server to server communication has been greatly enhanced, making it possible
to scale an application over several servers. One example of this is the ability
to run XML parsers, XSL transformations and even resource hungry session
objects on other servers.
Easy Configuration
√ Configuration of ASP.NET is done with plain text files.
√ Configuration files can be uploaded or changed while the application is running.
No need to restart the server. No more metabase or registry puzzle.
Easy Deployment
No more server restart to deploy or replace compiled code. ASP.NET simply redirects all new requests to the new code.