1. Which is the parent class of all the web server controls?
The System.Web.Ul.Control class is the parent
class for all Web server controls.
2. To which base class a Web form belongs to?
3. What method is used to sign out from forms authentication?
The FormsAuthentication.Signout() method is used
to sign out from the forms authentication.
4. What is PostBack?
Postback in
an event that is triggered when an action is performed by a control on asp.net
page. For example, when we click on a button, the data on the page
is posted back to the server for processing.
5. What is AutoPostBack property in asp.net?
If we want a control to postback automatically when an event is
raised, we set the control'sAutoPostBack property to True. If we
set AutoPostBack="true" on a control, then if value
changes, it will automatically postback to the server. The default value of this property is
FALSE.
6. What is IsPostBack property?
- IsPostBack is a Boolean property to
determine whether the page is being rendered/loaded for the first time or
is being loaded in response to a postback. Its values will be true if the page
is being loaded in response to a client postback
otherwise it will be false.
- Is Postback is normally
used on page _load event. When the page is loaded for the first time then
it means IsPostBack = false and when an event takes place it means
IsPostBack=true
Example:
private void Page_Load()
{
if (!IsPostBack)
{.
BindDropDownList();
}
}
In the above code snippet we are calling the method
BindDropDownList() on page load event because we always want to bind the
DropDownList control only once not on each occurrence of postback.
So this code to bind DropDowList will execute only once when this
page runs for the first time. On any other submit event this page will be
submitted to server but this block will not execute.
7. What is validation in asp.net?
Validation is
a process or technique of testing and ensuring that the user has entered
required and properly formatted information through the web form.
8. What is the difference between client-side and server-side
validations?
- Client-side validations take place at the client
side with the help of JavaScript and jQuery,AJAX etc before the Web page
is sent to the server whereas server-side validations take place at the server
end and done using programming languages like C#.Net,VB.Net etc.
- Client-side validation is
faster than server-side because it takes place on client side (on browser)
and the networking time from client to server is saved, whereas the
server-side validation is done on the web server and server renders the
data into html page and sends back to the client (browser). Thus it
is bit slower.
- Client side validation can
be bypassed by disabling the browser's JavaScript, so we should also
validate on the server side because it protects against the malicious
user, who can easily bypass our JavaScript and submit dangerous input to
the server.
9. What are the different validation controls in ASP.NET?
There are 6 validation controls which are:
- RequiredFieldValidator
- RangeValidator
- CompareValidator
- CustomValidator
- RegularExpressionValidator
- ValidationSummary
10. How to set the type of comparison
you want to perform by the CompareValidator control?
By setting the Operator property of the CompareValidator control.
11. What type of comparison can be
performed using CompareValidator by setting the operator property?
Following comparison can be performed:
- Equal: Checks whether the two
controls are equal to each other.
- NotEqual : Checks whether the
controls are not equal to each other.
- GreaterThan : Checks whether one control
is greater than the other control.
- GreaterThanEqual : Checks whether one control
is greater than or equal to the other control.
- LessThan: Checks whether one control
is less than the other control.
- LessThanEqual : Checks whether one control
is less than or equal to the other control.
- DataTypeCheck : Checks whether the data
types for the two controls are valid.
12. What is the use of
RequiredFieldValidator validation control?
RequiredFieldValidator control is used to ensure that the TextBox control can't be
left blank on before submitting to server. Check the article: How to use
RegularExpressionValidator validation control
13. What is the use of
RegularExpressionValidator validation control?
RegularExpressionValidator control is used to ensure that an input value matches a specified
pattern. For example: to check the email address and website URL validity
before submitting to server for processing. Check the article: How to use
RegularExpressionValidator validation control
14. What is the use
of CustomValidator validation control?
When no other validation control provided by visual studio
fulfills your validation requirement thenCustomValidator can do the job. As the name suggest,
CustomValidator can be customized as per application requirement.
CustomValidation control can be used to validate the controls client side or
server side both. Check the
article: How to use
CustomValidator validation control with example
15. What is the use of
CompareValidator validation control?
CompareValidator control is used to compare the value of one input control with the
value of other input control e.g. To compare the data in two TextBox controls
e.g. Password TextBox and Confirm password TextBox to ensure that the value
should be same before submitting to server for processing. Check the article: How to use
CompareValidator validation control with example
16. What is the use of
RangeValidator validation control?
RangeValidator control
is used to check the data entered is valid or not i.e. within the range
specified before submitting to server. Check the article: How to use
RangeValidator validation control with example
17. Which data type does
the RangeValidator control support?
RangeValidator control
supports the following data types:
- Integer
- Double
- String
- Currency
- Date
18. How to display all validation
messages in one control?
The ValidationSummary control displays all
validation messages in one control.
19. Differentiate between a Label
control and a Literal control?
Both the Label and Literal controls
allow you to statically or dynamically specify some text using the control's
Text property to get displayed on a web page.
The main difference between them is "Label"
control display the text wrapped in a HTML <span> tag. On the other hand,
literal control displays the clean text without wrapping it.
So Label control's final html code has an HTML <span> tag;
whereas, the Literal control's final html code contains only clean text, which
is not surrounded by any HTML tag.
Moreover Literal control does not let you apply any formatting and styles
whereas Label control does that.
20. What is the use of
the Global.asax file?
The Global.asax, also known as the ASP.NET application
file, is used to serve application-level and session-level events. It is option
file that reside in the application's root directory. External users cannot
download or view the code written within it because Global.asax file itself is
configured so that any direct URL request for it is automatically rejected.
21. How a custom server control can
be registered to a Web page?
@Register directive
is used to register a custom server control to a Web page.
22. How to assign page specific
attributes in an ASP.NET application?
Page specific attributes can be assigned using @Page directive.
23. What is a round trip?
In web programming concept, the trip of a web page from the client
to the server and then back to the client is called a round trip.
24. List some of the built-in
objects in Asp.Net?
The objects in ASP.NET are as follows:
- Application
- Request
- Response
- Server
- Session
- Context
- Trace
25. Which method is used to force
all the validation controls to run?
The Page.Validate() method is used to force all
the validation controls to run and to perform validation.
26. Differentiate
Response.Write() and Response.Output.Write() methods?
The Response.Write() method is used to
display the normal text output. Whereas, theResponse.Output.Write() method
is used to display the formatted text output.
For example:
Response.Write("Current Date Time is " +
DateTime.Now.ToString());
Response.Output.Write("{0} is {1:d}", "Current
formatted Date Time is: ", DateTime.Now);
27. What is the default expiration
time period for a Cookie?
The default expiration time period for a Cookie is 30 minutes.
28. What is the default expiration
time period for a session?
The default expiration time period for a session is 20 minutes.
29. What is the use
of PlaceHolder control?
The PlaceHolder control acts as a container for
storing the controls that are dynamically added to the web page at runtime. We
cannot see it at runtime because it does not produce any visible output, so it
is great for grouping content without the overhead of outer HTML tags.
30. What is the use
of Panel control?
The Panel control is a container for other controls. It is especially useful
when you want to generate controls programmatically, hide/show a group of
controls, or localize a group of controls. When rendering HTML: a PlaceHolder
control will render nothing, but Panel control will render as
a <div>.
31. Which method is used to destroy
explicitly a user's session?
The Session.Abandon() method destroys the
user session explicitly and release their occupied resources and
the Session_OnEnd event is triggered, so the user will be assigned a
new session id next time he/she visit the site . If we do not call
the Abandon method explicitly, the server destroys these objects when
the session times out.
32. What is the use of
Session.Clear()?
Session.Clear() clears
out all the keys and values stored in the session-state collection but it will
keep the user session, so the Session_End event will not be fired.
33. What is the difference between
a HyperLink and a LinkButton control?
The HyperLink control immediately navigates to the target
URL ( specified by the NavigateURL property) when the user clicks on the
control without posting back to server.
The LinkButton control first posts the form to the server,
and then navigates to the URL. So basically LinkButton is used If we need to do
any server-side processing before going to the target URL. So, if there is no
server-side processing required then don't waste a round trip and use the
HyperLink control.
A HyperLink control does not have the Click and Command events;
whereas, the LinkButton control has these events, which can be
handled in the code-behind file of the Web page.
34. Can we validate a DropDownList
by RequiredFieldValidator validation control?
Yes,
we can validate a DropDownList by RequiredFieldValidator. We have to set
the InitialValue property
of RequiredFieldValidator control.
For example:
<asp:DropDownList ID="ddlCity"
runat="server" Width="220px">
<asp:ListItem Value="0">-- Select City
--</asp:ListItem>
<asp:ListItem Value="1">Delhi</asp:ListItem>
<asp:ListItem
Value="2">Banglore</asp:ListItem>
<asp:ListItem
Value="3">Gurgaon</asp:ListItem>
<asp:ListItem Value="4">Pune</asp:ListItem>
</asp:DropDownList>
<asp:RequiredFieldValidator ID="rfvCity"
ControlToValidate="ddlCity"
InitialValue="0" runat="server"
ErrorMessage="Please select city"
SetFocusOnError="True"></asp:RequiredFieldValidator>
35. Can we validate a ListBox
by RequiredFieldValidator validation control?
Yes,
we can validate a ListBox by RequiredFieldValidator. We have to set the InitialValue property
of RequiredFieldValidator control.
For example:
<asp:ListBox ID="lstCity" runat="server"
Width="220px" SelectionMode="Multiple">
<asp:ListItem Value="0">-- Select City
--</asp:ListItem>
<asp:ListItem Value="1">Delhi</asp:ListItem>
<asp:ListItem
Value="2">Banglore</asp:ListItem>
<asp:ListItem
Value="3">Gurgaon</asp:ListItem>
<asp:ListItem Value="4">Pune</asp:ListItem>
</asp:ListBox>
<asp:RequiredFieldValidator ID="rfvValidateCity"
ControlToValidate="lstCity" InitialValue="0"
runat="server"
ErrorMessage="Please select atleast one city"
ForeColor="Red"
SetFocusOnError="True"></asp:RequiredFieldValidator>
36. What is ViewState?
ViewState is
used to retain the state of server-side objects between page post backs.
Whatever is stored in the view state can be accessed throughout the page
whenever required.
37. What is the lifespan for items
stored in ViewState?
They exist for the life of the current page.
38. Where is the ViewState data
stored?
View state data is stored in the client side(Webpage)
in the form of a hidden control(HTML hidden field) named
“__VIEWSTATE”
39. In which format ViewState data
is stored?
View State Data is stored in Base64 String encoded format which can be further decoded.
40. What is the difference between
Server.Transfer and Response.Redirect?
Both
Response.Redirect
and Server.Transfer
methods are used to
transfer a user from one web page to another web page. Both methods are used
for the same purpose, but still there are some differences as follows.
The
Response.Redirect
method redirects a
request to a new URL and specifies the new URL while theServer.Transfer
method for the
current request, terminates execution of the current page and starts execution
of a new page using the specified URL path of the page.