Dot Net Interview Questions

rb.sandhya@gmail.com (Monuments) — Tue, 10 Mar 2009 21:20:00 -0700

1.What is the use of web.config? Difference between machine.config and
Web.config?

ASP.NET configuration files are XML-based text files--each named web.config--that can
appear in any directory on an ASP.NET Web application server. Each web.config file
applies configuration settings to the directory it is located in and to all virtual child
directories beneath it. Settings in child directories can optionally override or modify
settings specified in parent directories. The root configuration file--
WinNT\Microsoft.NET\Framework\\config\machine.config--provides default
configuration settings for the entire machine. ASP.NET configures IIS to prevent direct
browser access to web.config files to ensure that their values cannot become public
(attempts to access them will cause ASP.NET to return 403: Access Forbidden). At run
time ASP.NET uses these web.config configuration files to hierarchically compute a
unique collection of settings for each incoming URL target request (these settings are
calculated only once and then cached across subsequent requests; ASP.NET
automatically watches for file changes and will invalidate the cache if any of the
configuration files change).

2.What is the use of sessionstate tag in the web.config file?
Configuring session state: Session state features can be configured via the section in a
web.config file. To double the default timeout of 20 minutes, you can add the following
to the web.config file of an application:

3.What are the different modes for the sessionstates in the web.config file?
•
Off -Indicates that session state is not enabled.
•
Inproc - Indicates that session state is stored locally.
•
StateServer-Indicates that session state is stored on a remote server.
•
SQLServer-Indicates that session state is stored on the SQL Server.

4.What is smart navigation?
When a page is requested by an Internet Explorer 5 browser, or later, smart navigation
enhances the user's experience of the page by performing the following:
•
eliminating the flash caused by navigation.
•
persisting the scroll position when moving from page to page.
•
persisting element focus between navigations.
•
retaining only the last page state in the browser's history.
Smart navigation is best used with ASP.NET pages that require frequent postbacks but
with visual content that does not change dramatically on return. Consider this carefully
when deciding whether to set this property to true.Set the SmartNavigation attribute to
true in the @ Page directive in the .aspx file. When the page is requested, the dynamically
generated class sets this property.

5.What base class do all Web Forms inherit from?
System.Web.UI.Page

Interview Question Part V

rb.sandhya@gmail.com (Monuments) — Tue, 10 Mar 2009 21:17:00 -0700

1.What are server controls?

ASP.NET server controls are components that run on the server and encapsulate user-
interface and other related functionality. They are used in ASP.NET pages and in
ASP.NET code-behind classes.

2.What is the difference between Web User Control and Web Custom Control?

Custom Controls
Web custom controls are compiled components that run on the server and that
encapsulate user-interface and other related functionality into reusable packages. They
can include all the design-time features of standard ASP.NET server controls, including
full support for Visual Studio design features such as the Properties window, the visual
designer, and the Toolbox.
There are several ways that you can create Web custom controls:
There are several ways that you can create Web custom controls:
•
You can compile a control that combines the functionality of two or more existing
controls. For example, if you need a control that encapsulates a button and a text
box, you can create it by compiling the existing controls together.
•
If an existing server control almost meets your requirements but lacks some
required features, you can customize the control by deriving from it and
overriding its properties, methods, and events.
•
If none of the existing Web server controls (or their combinations) meet your
requirements, you can create a custom control by deriving from one of the base
control classes. These classes provide all the basic functionality of Web server
controls, so you can focus on programming the features you need.
If none of the existing ASP.NET server controls meet the specific requirements of your
applications, you can create either a Web user control or a Web custom control that
encapsulates the functionality you need. The main difference between the two controls
lies in ease of creation vs. ease of use at design time.Web user controls are easy to make,
but they can be less convenient to use in advanced scenarios. You develop Web user
controls almost exactly the same way that you develop Web Forms pages. Like Web
Forms, user controls can be created in the visual designer, they can be written with code
separated from the HTML, and they can handle execution events. However, because Web
user controls are compiled dynamically at run time they cannot be added to the Toolbox,
and they are represented by a simple placeholder glyph when added to a page. This
makes Web user controls harder to use if you are accustomed to full Visual Studio .NET
design-time support, including the Properties window and Design view previews. Also,
the only way to share the user control between applications is to put a separate copy in
each application, which takes more maintenance if you make changes to the control.Web
custom controls are compiled code, which makes them easier to use but more difficult to
create; Web custom controls must be authored in code. Once you have created the
control, however, you can add it to the Toolbox and display it in a visual designer with
full Properties window support and all the other design-time features of ASP.NET server
controls. In addition, you can install a single copy of the Web custom control in the
global assembly cache and share it between applications, which makes maintenance
easier.
Web user controls
•
Easier to create
•
Limited support for consumers who use a visual design tool
•
A separate copy of the control is required in each application
•
Cannot be added to the Toolbox in Visual Studio
•
Good for static layout
Web custom controls
•
Harder to create
•
Full visual design tool support for consumers
•
Only a single copy of the control is required, in the global assembly cache
•
Can be added to the Toolbox in Visual Studio
•
Good for dynamic layout

3.Application and Session Events?

The ASP.NET page framework provides ways for you to work with events that can be
raised when your application starts or stops or when an individual user's session starts or
stops:
•
Application events are raised for all requests to an application. For example,
Application_BeginRequest is raised when any Web Forms page or XML Web
service in your application is requested. This event allows you to initialize
resources that will be used for each request to the application. A corresponding
event, Application_EndRequest, provides you with an opportunity to close or
otherwise dispose of resources used for the request
•
Session events are similar to application events (there is a Session_OnStart and a
Session_OnEnd event), but are raised with each unique session within the
application. A session begins when a user requests a page for the first time from
your application and ends either when your application explicitly closes the
session or when the session times out

4.Difference between ASP Session and ASP.NET Session?

asp.net session supports cookie less session & it can span across multiple servers.

5.What is cookie less session? How it works?

By default, ASP.NET will store the session state in the same process that processes the
request, just as ASP does. If cookies are not available, a session can be tracked by adding
a session identifier to the URL. This can be enabled by setting the following:
http://samples.gotdotnet.com/quickstart/aspplus/doc/stateoverview.aspx
6.How you will handle session when deploying application in more than a server?
Describe session handling in a webfarm, how does it work and what are the limits?
By default, ASP.NET will store the session state in the same process that processes the
request, just as ASP does. Additionally, ASP.NET can store session data in an external
process, which can even reside on another machine. To enable this feature:
•
Start the ASP.NET state service, either using the Services snap-in or by executing
"net start aspnet_state" on the command line. The state service will by default
listen on port 42424. To change the port, modify the registry key for the service:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aspnet_state\
Parameters\Port
•
Set the mode attribute of the section to "StateServer"
•
Configure the stateConnectionString attribute with the values of the machine on
which you started aspnet_state.
The following sample assumes that the state service is running on the same machine as
the Web server ("localhost") and uses the default port (42424): Note that if you try the
sample above with this setting, you can reset the Web server (enter iisreset on the
command line) and the session state value will persist.

7.What method do you use to explicitly kill a users session?
Abandon()

8.What are the different ways you would consider sending data across pages in ASP

(i.e between default.asp to default1.asp)?
•
Session
•
public properties

9.What is State Management in .Net and how many ways are there to maintain a
state in .Net? What is view state?

Web pages are recreated each time the page is posted to the server. In traditional Web
programming, this would ordinarily mean that all information associated with the page
and the controls on the page would be lost with each round trip. To overcome this
inherent limitation of traditional Web programming, the ASP.NET page framework
includes various options to help you preserve changes — that is, for managing state. The
page framework includes a facility called view state that automatically preserves property
values of the page and all the controls on it between round trips.However, you will
probably also have application-specific values that you want to preserve. To do so, you
can use one of the state management options.
Client-Based State Management Options:
•
View State
•
Hidden Form Fields
•
Cookies
•
Query Strings
Server-Based State Management Options:
•
Application State
•
Session State
•
Database Support

10.What are the disadvantages of view state / what are the benefits?

Automatic view-state management is a feature of server controls that enables them to
repopulate their property values on a round trip (without you having to write any code).
This feature does impact performance, however, since a server control's view state is
passed to and from the server in a hidden form field. You should be aware of when view
state helps you and when it hinders your page's performance.

11.When maintaining session through Sql server, what is the impact of Read and
Write operation on Session objects? will performance degrade?

Maintaining state using database technology is a common practice when storing user-
specific information where the information store is large. Database storage is particularly
useful for maintaining long-term state or state that must be preserved even if the server
must be restarted.

12.Explain the differences between Server-side and Client-side code?

Server side code will process at server side & it will send the result to client. Client side
code (javascript) will execute only at client side.

13.What are validator? Name the Validation controls in asp.net? How do u disable
them? Will the asp.net validators run in server side or client side? How do you do
Client-side validation in .Net? How to disable validator control by client side
JavaScript?

A set of server controls included with ASP.NET that test user input in HTML and Web
server controls for programmer-defined requirements. Validation controls perform input
checking in server code. If the user is working with a browser that supports DHTML, the
validation controls can also perform validation ("EnableClientScript" property set to
true/false) using client script.The following validation controls are available in
asp.net:RequiredFieldValidator Control, CompareValidator Control, RangeValidator
Control, RegularExpressionValidator Control, CustomValidator Control,
ValidationSummary Control.

14.Which two properties are there on every validation control?
ControlToValidate, ErrorMessage

15.How do you use css in asp.net?
Within the "" section of an HTML document that will use these styles, add a link to this
external CSS style sheet that follows this form: MyStyles.css is the name of your external
CSS style sheet.

16.How do you implement postback with a text box? What is postback and usestate?
Make AutoPostBack property to true

17.What is SQL injection?
An SQL injection attack "injects" or manipulates SQL code by adding unexpected SQL
to a query.Many web pages take parameters from web user, and make SQL query to the
database. Take for instance when a user login, web page that user name and password
and make SQL query to the database to check if a user has valid name and
password.Username: ' or 1=1 --- Password: [Empty]This would execute the following
query against the users table: select count(*) from users where userName='' or 1=1 --' and
userPass=''

Interview Questions Part IV

rb.sandhya@gmail.com (Monuments) — Tue, 10 Mar 2009 21:10:00 -0700

1.Advantage of ADO.Net?

ADO.NET Does Not Depend On Continuously Live Connections.
•
Database Interactions Are Performed Using Data Commands.
•
Data Can Be Cached in Datasets.
•
Datasets Are Independent of Data Sources.
•
Data Is Persisted as XML.
•
Schemas Define Data Structures

2.How would u connect to database using .NET?

SqlConnection nwindConn = new SqlConnection("Data Source=localhost; Integrated
Security=SSPI;" + "Initial Catalog=northwind");nwindConn.Open();

3.What are relation objects in dataset and how & where to use them?

In a DataSet that contains multiple DataTable objects, you can use DataRelation objects
to relate one table to another, to navigate through the tables, and to return child or parent
rows from a related table. Adding a DataRelation to a DataSet adds, by default, a
UniqueConstraint to the parent table and a ForeignKeyConstraint to the child table.

4.Difference between OLEDB Provider and SqlClient ?

SQLClient .NET classes are highly optimized for the .net / sqlserver combination and
achieve optimal results. The SqlClient data provider is fast. It's faster than the Oracle
provider, and faster than accessing database via the OleDb layer. It's faster because it
accesses the native library (which automatically gives you better performance), and it
was written with lots of help from the SQL Server team.

5.What are the different namespaces used in the project to connect the database?

What data providers available in .net to connect to database?
System.Data.OleDb – classes that make up the .NET Framework Data Provider for OLE
DB-compatible data sources. These classes allow you to connect to an OLE DB data
source, execute commands against the source, and read the results.
System.Data.SqlClient – classes that make up the .NET Framework Data Provider for
SQL Server, which allows you to connect to SQL Server 7.0, execute commands, and
read results. The System.Data.SqlClient namespace is similar to the System.Data.OleDb
namespace, but is optimized for access to SQL Server 7.0 and later.
System.Data.Odbc - classes that make up the .NET Framework Data Provider for
ODBC. These classes allow you to access ODBC data source in the managed space.
System.Data.OracleClient - classes that make up the .NET Framework Data Provider for
Oracle. These classes allow you to access an Oracle data source in the managed space.

6.Difference between DataReader and DataAdapter / DataSet and DataAdapter?

You can use the ADO.NET DataReader to retrieve a read-only, forward-only stream of
data from a database. Using the DataReader can increase application performance and
reduce system overhead because only one row at a time is ever in memory.After creating
an instance of the Command object, you create a DataReader by calling
Command.ExecuteReader to retrieve rows from a data source, as shown in the following
example.SqlDataReader myReader = myCommand.ExecuteReader();You use the Read
method of the DataReader object to obtain a row from the results of the query.while
(myReader.Read()) Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0),
myReader.GetString(1));myReader.Close();The DataSet is a memory-resident
representation of data that provides a consistent relational programming model regardless
of the data source. It can be used with multiple and differing data sources, used with
XML data, or used to manage data local to the application. The DataSet represents a
complete set of data including related tables, constraints, and relationships among the
tables. The methods and objects in a DataSet are consistent with those in the relational
database model. The DataSet can also persist and reload its contents as XML and its
schema as XML Schema definition language (XSD) schema.The DataAdapter serves as a
bridge between a DataSet and a data source for retrieving and saving data. The
DataAdapter provides this bridge by mapping Fill, which changes the data in the DataSet
to match the data in the data source, and Update, which changes the data in the data
source to match the data in the DataSet. If you are connecting to a Microsoft SQL Server
database, you can increase overall performance by using the SqlDataAdapter along with
its associated SqlCommand and SqlConnection. For other OLE DB-supported databases,
use the DataAdapter with its associated OleDbCommand and OleDbConnection objects.

7.What happens when we issue Dataset.ReadXml command?

Reads XML schema and data into the DataSet.

Interview Question Part III

rb.sandhya@gmail.com (Monuments) — Tue, 10 Mar 2009 21:01:00 -0700

12.Can we call a base class method without creating instance?

Its possible If its a static method.
Its possible by inheriting from that class also.
Its possible from derived classes using base keyword.

13.What are Sealed Classes in C#?

The sealed modifier is used to prevent derivation from a class. A compile-time error
occurs if a sealed class is specified as the base class of another class. (A sealed class
cannot also be an abstract class)

14.In which Scenario you will go for Interface or Abstract Class?

Interfaces, like classes, define a set of properties, methods, and events. But unlike classes,
interfaces do not provide implementation. They are implemented by classes, and defined
as separate entities from classes. Even though class inheritance allows your classes to
inherit implementation from a base class, it also forces you to make most of your design
decisions when the class is first published.Abstract classes are useful when creating
components because they allow you specify an invariant level of functionality in some
methods, but leave the implementation of other methods until a specific implementation
of that class is needed. They also version well, because if additional functionality is
needed in derived classes, it can be added to the base class without breaking code.

15.What are the access-specifiers available in c#?

Private, Protected, Public, Internal, Protected Internal.

16.Explain about Protected and protected internal, “internal” access-specifier?

protected - Access is limited to the containing class or types derived from the
containing class.
•
internal - Access is limited to the current assembly.
•
protected internal - Access is limited to the current assembly or types derived
from the containing class.

17.Difference between type constructor and instance constructor? What is static
constructor, when it will be fired? And what is its use?

(Class constructor method is also known as type constructor or type initializer)Instance
constructor is executed when a new instance of type is created and the class constructor is
executed after the type is loaded and before any one of the type members is accessed. (It
will get executed only 1st time, when we call any static methods/fields in the same class.)
Class constructors are used for static field initialization. Only one class constructor per
type is permitted, and it cannot use the vararg (variable argument) calling convention.A
static constructor is used to initialize a class. It is called automatically to initialize the
class before the first instance is created or any static members are referenced.

18.What is Private Constructor? and it’s use? Can you create instance of a class
which has Private Constructor?

When a class declares only private instance constructors, it is not possible for classes
outside the program to derive from the class or to directly create instances of it. (Except
Nested classes)
Make a constructor private if:- You want it to be available only to the class itself. For
example, you might have a special constructor used only in the implementation of your
class' Clone method.- You do not want instances of your component to be created. For
example, you may have a class containing nothing but Shared utility functions, and no
instance data. Creating instances of the class would waste memory.

19.What are Destructor and finalize?

Generally in C++ the destructor is called when objects gets destroyed. And one can
explicitly call the destructors in C++. And also the objects are destroyed in reverse order
that they are created in. So in C++ you have control over the destructors.In C# you can
never call them, the reason is one cannot destroy an object. So who has the control over
the destructor (in C#)? it's the .Net frameworks Garbage Collector (GC). GC destroys the
objects only when necessary. Some situations of necessity are memory is exhausted or
user explicitly calls System.GC.Collect() method.Points to remember:
•
Destructors cannot be overloaded. Thus, a class can have, at most, one destructor.
•
Destructors are invoked automatically, and cannot be invoked explicitly
•
Destructors are not inherited. Thus, a class has no destructors other than the one,
which may be declared in it.
•
Destructors cannot be used with structs. They are only used with classes.
•
An instance becomes eligible for destruction when it is no longer possible for any
code to use the instance.
•
Execution of the destructor for the instance may occur at any time after the
instance becomes eligible for destruction.
•
When an instance is destructed, the destructors in its inheritance chain are called,
in order, from most derived to least derived.
http://msdn.microsoft.com/library/default.asp?url=/library/en-
us/cpguide/html/cpconfinalizemethodscdestructors.asp

20.What is the difference between Finalize and Dispose (Garbage collection)?

Class instances often encapsulate control over resources that are not managed by the
runtime, such as window handles (HWND), database connections, and so on. Therefore,
you should provide both an explicit and an implicit way to free those resources. Provide
implicit control by implementing the protected Finalize Method on an object (destructor
syntax in C# and the Managed Extensions for C++). The garbage collector calls this
method at some point after there are no longer any valid references to the object.In some
cases, you might want to provide programmers using an object with the ability to
explicitly release these external resources before the garbage collector frees the object. If
an external resource is scarce or expensive, better performance can be achieved if the
programmer explicitly releases resources when they are no longer being used. To provide
explicit control, implement the Dispose method provided by the IDisposable Interface.
The consumer of the object should call this method when it is done using the object.
Dispose can be called even if other references to the object are alive.Note that even when
you provide explicit control by way of Dispose, you should provide implicit cleanup
using the Finalize method. Finalize provides a backup to prevent resources from
permanently leaking if the programmer fails to call Dispose

21.What is boxing & unboxing?

Boxing:http://www.codersource.net/csharp_boxing_unboxing.html

22.Is goto statement supported in C#?

Gotos are supported in C#to the fullest.

23.What’s different about switch statements in C#?

No fall-throughs allowed. Unlike the C++ switch statement, C# does not support an
explicit fall through from one case label to another. If you want, you can use goto a
switch-case, or goto default.
case 1:
cost += 25;
break;
case 2:
cost += 25;
goto case 1;

Interview Question Part III

rb.sandhya@gmail.com (Monuments) — Tue, 10 Mar 2009 20:58:00 -0700

1.What is Active Directory? What is the namespace used to access the Microsoft
Active Directories? What are ADSI Directories?

Active Directory Service Interfaces (ADSI) is a programmatic interface for Microsoft
Windows Active Directory. It enables your applications to interact with diverse
directories on a network, using a single interface. Visual Studio .NET and the .NET
Framework make it easy to add ADSI functionality with the DirectoryEntry and
DirectorySearcher components.Using ADSI, you can create applications that perform
common administrative tasks, such as backing up databases, accessing printers, and
administering user accounts. ADSI makes it possible for you to:
Log on once to work with diverse directories. The DirectoryEntry component class
provides username and password properties that can be entered at runtime and
communicated to the Active Directory object you are binding to.
Use a single application programming interface (API) to perform tasks on multiple
directory systems by offering the user a variety of protocols to use. The
DirectoryServices namespace provides the classes to perform most administrative
functions.
Perform "rich querying" on directory systems. ADSI technology allows for searching for
an object by specifying two query dialects: SQL and LDAP.
Access and use a single, hierarchical structure for administering and maintaining diverse
and complicated network configurations by accessing an Active Directory tree.
Integrate directory information with databases such as SQL Server. The DirectoryEntry
path may be used as an ADO.NET connection string provided that it is using the LDAP
provider. using System.DirectoryServices;

2.What are Namespaces?

The namespace keyword is used to declare a scope. This namespace scope lets you
organize code and gives you a way to create globally-unique types. Even if you do not
explicitly declare one, a default namespace is created. This unnamed namespace,
sometimes called the global namespace, is present in every file. Any identifier in the
global namespace is available for use in a named namespace. Namespaces implicitly have
public access and this is not modifiable

3.What is the difference between CONST and READONLY?

Both are meant for constant values. A const field can only be initialized at the declaration
of the field. A readonly field can be initialized either at the declaration or in a constructor.
Therefore, readonly fields can have different values depending on the constructor used.
readonly int b;public X(){b=1;}public X(string s){b=5;}public X(string s, int
i){b=i;}Also, while a const field is a compile-time constant, the readonly field can be
used for runtime constants, as in the following example:public static readonly uint l1 =
(uint) DateTime.Now.Ticks; (this can't be possible with const)

4. What is the difference between ref & out parameters?

An argument passed to a ref parameter must first be initialized. Compare this to an out
parameter, whose argument does not have to be explicitly initialized before being passed
to an out parameter.

5.What is the difference between Array and Arraylist?

As elements are added to an ArrayList, the capacity is automatically increased as required
through reallocation. The capacity can be decreased by calling TrimToSize or by setting
the Capacity property explicitly.

6. What is Jagged Arrays?

A jagged array is an array whose elements are arrays. The elements of a jagged array can
be of different dimensions and sizes. A jagged array is sometimes called an "array-of-
arrays.

7.What are indexers?

Indexers are similar to properties, except that the get and set accessors of indexers take
parameters, while property accessors do not.

8.What is the difference between a Struct and a Class?

a.The struct type is suitable for representing lightweight objects such as Point, Rectangle,
and Color. Although it is possible to represent a point as a class, a struct is more efficient
in some scenarios. For example, if you declare an array of 1000 Point objects, you will
allocate additional memory for referencing each object. In this case, the struct is less
expensive.
b.When you create a struct object using the new operator, it gets created and the
appropriate constructor is called. Unlike classes, structs can be instantiated without using
the new operator. If you do not use new, the fields will remain unassigned and the object
cannot be used until all of the fields are initialized.
c.It is an error to declare a default (parameterless) constructor for a struct. A default
constructor is always provided to initialize the struct members to their default values.
d.It is an error to initialize an instance field in a struct.
e.There is no inheritance for structs as there is for classes. A struct cannot inherit from
another struct or class, and it cannot be the base of a class. Structs, however, inherit from
the base class Object. A struct can implement interfaces, and it does that exactly as
classes do
f.A struct is a value type, while a class is a reference type

9.Value type & reference types difference? Example from .NET. Integer & struct
are value types or reference types in .NET?

Most programming languages provide built-in data types, such as integers and floating-
point numbers, that are copied when they are passed as arguments (that is, they are
passed by value). In the .NET Framework, these are called value types. The runtime
supports two kinds of value types:
•
Built-in value types
The .NET Framework defines built-in value types, such as System.Int32 and
System.Boolean, which correspond and are identical to primitive data types used by
programming languages.
•
User-defined value types
Your language will provide ways to define your own value types, which derive from
System.ValueType. If you want to define a type representing a value that is small, such as
a complex number (using two floating-point numbers), you might choose to define it as a
value type because you can pass the value type efficiently by value. If the type you are
defining would be more efficiently passed by reference, you should define it as a class
instead.
Variables of reference types, referred to as objects, store references to the actual data.
This following are the reference types:
•
class
•
interface
•
delegate
This following are the built-in reference types:
•
object
•
string

10.What is Method overloading?

Method overloading occurs when a class contains two methods with the same name, but
different signatures.

11.What is Method Overriding? How to override a function in C#?

Use the override modifier to modify a method, a property, an indexer, or an event. An
override method provides a new implementation of a member inherited from a base class.
The method overridden by an override declaration is known as the overridden base
method. The overridden base method must have the same signature as the override
method.You cannot override a non-virtual or static method. The overridden base method
must be virtual, abstract, or override.

Interview Topics

rb.sandhya@gmail.com (Monuments) — Tue, 10 Mar 2009 20:55:00 -0700

10.What is Garbage Collection in .Net? Garbage collection process?

The process of transitively tracing through all pointers to actively used objects in order to
locate all objects that can be referenced, and then arranging to reuse any heap memory
that was not found during this trace. The common language runtime garbage collector
also compacts the memory that is in use to reduce the working space needed for the heap.

11.What is Reflection in .NET? Namespace? How will you load an assembly which is
not referenced by current assembly?

All .NET compilers produce metadata about the types defined in the modules they
produce. This metadata is packaged along with the module (modules in turn are packaged
together in assemblies), and can be accessed by a mechanism called reflection. The
System.Reflection namespace contains classes that can be used to interrogate the types
for a module/assembly.Using reflection to access .NET metadata is very similar to using
ITypeLib/ITypeInfo to access type library data in COM, and it is used for similar
purposes - e.g. determining data type sizes for marshaling data across
context/process/machine boundaries.Reflection can also be used to dynamically invoke
methods (see System.Type.InvokeMember), or even create types dynamically at run-time
(see System.Reflection.Emit.TypeBuilder).

interview Questions Part II

rb.sandhya@gmail.com (Monuments) — Tue, 10 Mar 2009 20:50:00 -0700

1.What is Assembly?

Assemblies are the building blocks of .NET Framework applications; they form the
fundamental unit of deployment, version control, reuse, activation scoping, and security
permissions. An assembly is a collection of types and resources that are built to work
together and form a logical unit of functionality. An assembly provides the common
language runtime with the information it needs to be aware of type implementations. To
the runtime, a type does not exist outside the context of an assembly.Assemblies are a
fundamental part of programming with the .NET Framework. An assembly performs the
following functions: It contains code that the common language runtime executes.
Microsoft intermediate language (MSIL) code in a portable executable (PE) file will not
be executed if it does not have an associated assembly manifest. Note that each assembly
can have only one entry point (that is, DllMain, WinMain, or Main). It forms a security
boundary. An assembly is the unit at which permissions are requested and granted. It
forms a type boundary. Every type's identity includes the name of the assembly in which
it resides. A type called MyType loaded in the scope of one assembly is not the same as a
type called MyType loaded in the scope of another assembly. It forms a reference scope
boundary. The assembly's manifest contains assembly metadata that is used for resolving
types and satisfying resource requests. It specifies the types and resources that are
exposed outside the assembly. The manifest also enumerates other assemblies on which it
depends. It forms a version boundary. The assembly is the smallest versionable unit in the
common language runtime; all types and resources in the same assembly are versioned as
a unit. The assembly's manifest describes the version dependencies you specify for any
dependent assemblies. It forms a deployment unit. When an application starts, only the
assemblies that the application initially calls must be present. Other assemblies, such as
localization resources or assemblies containing utility classes, can be retrieved on
demand. This allows applications to be kept simple and thin when first downloaded. It is
the unit at which side-by-side execution is supported. Assemblies can be static or
dynamic. Static assemblies can include .NET Framework types (interfaces and classes),
as well as resources for the assembly (bitmaps, JPEG files, resource files, and so on).
Static assemblies are stored on disk in PE files. You can also use the .NET Framework to
create dynamic assemblies, which are run directly from memory and are not saved to disk
before execution. You can save dynamic assemblies to disk after they have
executed.There are several ways to create assemblies. You can use development tools,
such as Visual Studio .NET, that you have used in the past to create .dll or .exe files. You
can use tools provided in the .NET Framework SDK to create assemblies with modules
created in other development environments. You can also use common language runtime
APIs, such as Reflection.Emit, to create dynamic assemblies

2.What are the contents of assembly?

In general, a static assembly can consist of four elements: 1.The assembly manifest,
which contains assembly metadata. 2.Type metadata. 3.Microsoft intermediate language
(MSIL) code that implements the types. 4. A set of resources.

3.What are the different types of assemblies?

Private, Public/Shared, Satellite

4.What is the difference between a private assembly and a shared assembly?

a. Location and visibility: A private assembly is normally used by a single application,
and is stored in the application's directory, or a sub-directory beneath. A shared assembly
is normally stored in the global assembly cache, which is a repository of assemblies
maintained by the .NET runtime. Shared assemblies are usually libraries of code which
many applications will find useful, e.g. the .NET framework classes.
b. Versioning: The runtime enforces versioning constraints only on shared assemblies,
not on private assemblies.

5.What are Satellite Assemblies? How you will create this? How will you get the
different language strings?

Satellite assemblies are often used to deploy language-specific resources for an
application. These language-specific assemblies work in side-by-side execution because
the application has a separate product ID for each language and installs satellite
assemblies in a language-specific subdirectory for each language. When uninstalling, the
application removes only the satellite assemblies associated with a given language and
.NET Framework version. No core .NET Framework files are removed unless the last
language for that .NET Framework version is being removed.(For example, English and
Japanese editions of the .NET Framework version 1.1 share the same core files. The
Japanese .NET Framework version 1.1 adds satellite assemblies with localized resources
in a \ja subdirectory. An application that supports the .NET Framework version 1.1,
regardless of its language, always uses the same core runtime
files.)

6.What is Assembly manifest? what all details the assembly manifest will contain?

Every assembly, whether static or dynamic, contains a collection of data that describes
how the elements in the assembly relate to each other. The assembly manifest contains
this assembly metadata. An assembly manifest contains all the metadata needed to
specify the assembly's version requirements and security identity, and all metadata
needed to define the scope of the assembly and resolve references to resources and
classes. The assembly manifest can be stored in either a PE file (an .exe or .dll) with
Microsoft intermediate language (MSIL) code or in a standalone PE file that contains
only assembly manifest information.It contains Assembly name, Version number,
Culture, Strong name information, List of all files in the assembly, Type reference
information, Information on referenced assemblies.

7.Difference between assembly manifest & metadata?

assembly manifest - An integral part of every assembly that renders the assembly self-
describing. The assembly manifest contains the assembly's metadata. The manifest
establishes the assembly identity, specifies the files that make up the assembly
implementation, specifies the types and resources that make up the assembly, itemizes the
compile-time dependencies on other assemblies, and specifies the set of permissions
required for the assembly to run properly. This information is used at run time to resolve
references, enforce version binding policy, and validate the integrity of loaded
assemblies. The self-describing nature of assemblies also helps makes zero-impact install
and XCOPY deployment feasible.
metadata - Information that describes every element managed by the common language
runtime: an assembly, loadable file, type, method, and so on. This can include
information required for debugging and garbage collection, as well as security attributes,
marshaling data, extended class and member definitions, version binding, and other
information required by the runtime.

8.What is Global Assembly Cache (GAC) and what is the purpose of it? (How to
make an assembly to public? Steps) How more than one version of an assembly can
keep in same place?

Each computer where the common language runtime is installed has a machine-wide
code cache called the global assembly cache. The global assembly cache stores
assemblies specifically designated to be shared by several applications on the computer.
You should share assemblies by installing them into the global assembly cache only
when you need to.Steps- Create a strong name using sn.exe tooleg: sn -k keyPair.snk-
with in AssemblyInfo.cs add the generated file name eg: [assembly:
AssemblyKeyFile("abc.snk")]- recompile project, then install it to GAC by eitherdrag &
drop it to assembly folder (C:\WINDOWS\assembly OR C:\WINNT\assembly)
(shfusion.dll tool)orgacutil -i abc.dll

9.How to find methods of a assembly file (not using ILDASM)
By using Reflection .

Interview Question On Dot Net

rb.sandhya@gmail.com (Monuments) — Tue, 10 Mar 2009 20:44:00 -0700

16.What is Custom attribute? How to create? If I'm having custom attribute in an
assembly, how to say that name in the code?

A: The primary steps to properly design custom attribute classes are as follows:
Applying the AttributeUsageAttribute ([AttributeUsage(AttributeTargets.All, Inherited =
false, AllowMultiple = true)])
Declaring the attribute. (class public class MyAttribute : System.Attribute { // . . . })
Declaring constructors (public MyAttribute(bool myvalue) { this.myvalue = myvalue; })
Declaring properties public bool MyProperty{get {return this.myvalue;}set {this.myvalue
= value;}} The following example demonstrates the basic way of using reflection to get
access to custom attributes. class MainClass {public static void
Main(){System.Reflection.MemberInfo info = typeof(MyClass);object[] attributes =
info.GetCustomAttributes();for (int i = 0; i <>

17.What is the managed and unmanaged code in .net?

The .NET Framework provides a run-time environment called the Common Language
Runtime, which manages the execution of code and provides services that make the
development process easier. Compilers and tools expose the runtime's functionality and
enable you to write code that benefits from this managed execution environment. Code
that you develop with a language compiler that targets the runtime is called managed
code; it benefits from features such as cross-language integration, cross-language
exception handling, enhanced security, versioning and deployment support, a simplified
model for component interaction, and debugging and profiling services.

18.using directive VS using statement
You create an instance in a using statement to ensure that Dispose is called on the object
when the using statement is exited. A using statement can be exited either when the end
of the using statement is reached or if, for example, an exception is thrown and control
leaves the statement block before the end of the statement.The using directive has two
uses:
a.Create an alias for a namespace (a using alias).
b.Permit the use of types in a namespace, such that, you do not have to qualify the use of
a type in that namespace (a using directive).

19.Describe the Managed Execution Process?

The managed execution process includes the following steps:
a.Choosing a compiler. To obtain the benefits provided by the common language
runtime, you must use one or more language compilers that target the runtime.
b.Compiling your code to Microsoft intermediate language (MSIL). Compiling translates
your source code into MSIL and generates the required metadata.
c.Compiling MSIL to native code. At execution time, a just-in-time (JIT) compiler
translates the MSIL into native code. During this compilation, code must pass a
verification process that examines the MSIL and metadata to find out whether the code
can be determined to be type safe.
d.Executing your code. The common language runtime provides the infrastructure that
enables execution to take place as well as a variety of services that can be used during
execution.

20.How Garbage Collector (GC) Works?

The methods in this class influence when an object is garbage collected and when
resources allocated by an object are released. Properties in this class provide information
about the total amount of memory available in the system and the age category, or
generation, of memory allocated to an object. Periodically, the garbage collector performs
garbage collection to reclaim memory allocated to objects for which there are no valid
references. Garbage collection happens automatically when a request for memory cannot
be satisfied using available free memory. Alternatively, an application can force garbage
collection using the Collect method.Garbage collection consists of the following steps:
a.The garbage collector searches for managed objects that are referenced in managed
code.
b.The garbage collector attempts to finalize objects that are not referenced.
c.The garbage collector frees objects that are not referenced and reclaims their memory.

21.Why do we need to call CG.SupressFinalize?

Requests that the system not call the finalizer method for the specified object. [C#]public
static void SuppressFinalize( object obj); The method removes obj from the set of objects
that require finalization. The obj parameter is required to be the caller of this
method.Objects that implement the IDisposable interface can call this method from the
IDisposable.Dispose method to prevent the garbage collector from calling Object.Finalize
on an object that does not require it.

22.What is nmake tool?

The Nmake tool (Nmake.exe) is a 32-bit tool that you use to build projects based oncommands contained in a .mak file.usage

rb.sandhya@gmail.com (Monuments) — Tue, 10 Mar 2009 20:37:00 -0700

9.What is Code Access Security (CAS)?CAS is the part of the .NET security model that determines whether or not a piece ofcode is allowed to run, and what resources it can use when it is running. For example, itis CAS that will prevent a .NET web applet from formatting your hard disk.How does CAS work?

The CAS security policy revolves around two key concepts - code groups andpermissions. Each .NET assembly is a member of a particular code group, and each codegroup is granted the permissions specified in a named permission set. For example, usingthe default security policy, a control downloaded from a web site belongs to the 'Zone -Internet' code group, which adheres to the permissions defined by the 'Internet' namedpermission set. (Naturally the 'Internet' named permission set represents a very restrictiverange of permissions.)

Who defines the CAS code groups?Microsoft defines some default ones, but you can modify these and even create your own.To see the code groups defined on your system, run 'caspol -lg' from the command-line.

10.Which namespace is the base class for .net Class library?

Ans: system.object

11.What are object pooling and connection pooling and difference?

Where do we setthe Min and Max Pool size for connection pooling?Object pooling is a COM+ service that enables you to reduce the overhead of creatingeach object from scratch. When an object is activated, it is pulled from the pool. Whenthe object is deactivated, it is placed back into the pool to await the next request. You canconfigure object pooling by applying the ObjectPoolingAttribute attribute to a class thatderives from the System.EnterpriseServices.ServicedComponent class. Object poolinglets you control the number of connections you use, as opposed to connection pooling,where you control the maximum number reached.Following are important differencesbetween object pooling and connection pooling:Creation. When using connection pooling, creation is on the same thread, so if there isnothing in the pool, a connection is created on your behalf. With object pooling, the poolmight decide to create a new object. However, if you have already reached yourmaximum, it instead gives you the next available object. This is crucial behavior when ittakes a long time to create an object, but you do not use it for very long.Enforcement of minimums and maximums. This is not done in connection pooling. Themaximum value in object pooling is very important when trying to scale your application.You might need to multiplex thousands of requests to just a few objects. (TPC/Cbenchmarks rely on this.)COM+ object pooling is identical to what is used in .NET Framework managed SQLClient connection pooling. For example, creation is on a different thread and minimumsand maximums are enforced.

12.What is Application Domain?

The primary purpose of the AppDomain is to isolate an application from otherapplications. Win32 processes provide isolation by having distinct memory addressspaces. This is effective, but it is expensive and doesn't scale well. The .NET runtimeenforces AppDomain isolation by keeping control over the use of memory - all memoryin the AppDomain is managed by the .NET runtime, so the runtime can ensure thatAppDomains do not access each other's memory.Objects in different application domainscommunicate either by transporting copies of objects across application domainboundaries, or by using a proxy to exchange messages.MarshalByRefObject is the baseclass for objects that communicate across application domain boundaries by exchangingmessages using a proxy. Objects that do not inherit from MarshalByRefObject areimplicitly marshal by value. When a remote application references a marshal by valueobject, a copy of the object is passed across application domain boundaries.

How does an AppDomain get created?

AppDomains are usually created by hosts. Examples of hostsare the Windows Shell, ASP.NET and IE. When you run a .NET application from thecommand-line, the host is the Shell. The Shell creates a new AppDomain for everyapplication.AppDomains can also be explicitly created by .NET applications. Here is aC# sample which creates an AppDomain, creates an instance of an object inside it, andthen executes one of the object's methods.

13.What is serialization in .NET?

What are the ways to control serialization?Serialization is the process of converting an object into a stream of bytes. Deserializationis the opposite process of creating an object from a stream of bytes.Serialization/Deserialization is mostly used to transport objects (e.g. during remoting), orto persist objects (e.g. to a file or database).Serialization can be defined as the process ofstoring the state of an object to a storage medium. During this process, the public andprivate fields of the object and the name of the class, including the assembly containingthe class, are converted to a stream of bytes, which is then written to a data stream. Whenthe object is subsequently deserialized, an exact clone of the original object is created.Binary serialization preserves type fidelity, which is useful for preserving the state of anobject between different invocations of an application. For example, you can share anobject between different applications by serializing it to the clipboard. You can serializean object to a stream, disk, memory, over the network, and so forth. Remoting usesserialization to pass objects "by value" from one computer or application domain toanother.XML serialization serializes only public properties and fields and does not preserve typefidelity. This is useful when you want to provide or consume data without restricting theapplication that uses the data. Because XML is an open standard, it is an attractive choicefor sharing data across the Web. SOAP is an open standard, which makes it an attractivechoice. There are two separate mechanisms provided by the .NET class library -XmlSerializer and SoapFormatter/BinaryFormatter. Microsoft uses XmlSerializer forWeb Services, and uses SoapFormatter/BinaryFormatter for remoting. Both are availablefor use in your own code.

14.Why do I get errors when I try to serialize a Hashtable?

XmlSerializer will refuse to serialize instances of any class that implements IDictionary,e.g. Hashtable. SoapFormatter and BinaryFormatter do not have this restriction.

15.What is exception handling?

When an exception occurs, the system searches for the nearest catch clause that canhandle the exception, as determined by the run-time type of the exception. First, thecurrent method is searched for a lexically enclosing try statement, and the associatedcatch clauses of the try statement are considered in order. If that fails, the method thatcalled the current method is searched for a lexically enclosing try statement that enclosesthe point of the call to the current method. This search continues until a catch clause isfound that can handle the current exception, by naming an exception class that is of thesame class, or a base class, of the run-time type of the exception being thrown. A catchclause that doesn't name an exception class can handle any exception.Once a matchingcatch clause is found, the system prepares to transfer control to the first statement of thecatch clause. Before execution of the catch clause begins, the system first executes, inorder, any finally clauses that were associated with try statements more nested that thanthe one that caught the exception. Exceptions that occur during destructor execution areworth special mention. If an exception occurs during destructor execution, and thatexception is not caught, then the execution of that destructor is terminated and thedestructor of the base class (if any) is called. If there is no base class (as in the case of theobject type) or if there is no base class destructor, then the exception is discarded.

Dot Nte Interview Questions

rb.sandhya@gmail.com (Monuments) — Tue, 10 Mar 2009 20:33:00 -0700

1. What is .NET Framework?
The .NET framework created by Microsoft is a software development platform focused
on rapid application development, platform independence and network transparency.
.NET is Microsoft's strategic initiative for server and desktop development for the next
decade. According to Microsoft, .NET includes many technologies that are designed to
facilitate rapid development of Internet and intranet applications.

2. Is .NET a runtime service or a development platform?
It's both and actually a lot more. Microsoft .NET includes a new way of delivering
software and services to businesses and consumers. A part of Microsoft.NET is the .NET
Frameworks. The .NET frameworks SDK consists of two parts: the .NET common
language runtime and the .NET class library. In addition, the SDK also includes
command-line compilers for C#, C++, JScript, and VB. You use these compilers to build
applications and components. These components require the runtime to execute so this is
a development platform.

3.What is a IL? or what is MSIL?What is JIT?
(IL)Intermediate Language is also known as MSIL (Microsoft Intermediate Language) or
CIL (Common Intermediate Language). All .NET source code is compiled to IL. This IL
is then converted to machine code at the point where the software is installed, or at run-
time by a Just-In- Time (JIT) compiler.

4. Can we write IL programs directly?
Yes.
assembly
MyAssembly {
}
.class MyApp {
.method static void Main() {
.entrypoint ldstr "Hello, IL!" call
void System.Console::WriteLine(class System.Object)
ret }
}
Just put this into a file called hello.il, and then run ilasm hello.il. An exe assembly will be
generated.Can I do things in IL that I can't do in C#?Yes. A couple of simple examples
are that you can throw exceptions that are not derived from System.Exception, and you
can have non-zero-based arrays.

5.What is JIT (just in time)?
how it works?Before Microsoft intermediate language (MSIL) can be executed, it must
be converted by a .NET Framework just-in-time (JIT) compiler to native code, which is
CPU-specific code that runs on the same computer architecture as the JIT compiler.
Rather than using time and memory to convert all the MSIL in a portable executable (PE)
file to native code, it converts the MSIL as it is needed during execution and stores the
resulting native code so that it is accessible for subsequent calls.The runtime supplies
another mode of compilation called install-time code generation. The install-time code
generation mode converts MSIL to native code just as the regular JIT compiler does, but
it converts larger units of code at a time, storing the resulting native code for use when
the assembly is subsequently loaded and executed.As part of compiling MSIL to native
code, code must pass a verification process unless an administrator has established a
security policy that allows code to bypass verification. Verification examines MSIL and
metadata to find out whether the code can be determined to be type safe, which means
that it is known to access only the memory locations it is authorized to access.

6. What is strong name?
A name that consists of an assembly's identity—its simple text name, version number,
and culture information (if provided)—strengthened by a public key and a digital
signature generated over the assembly.

7. What is portable executable (PE)?
The file format defining the structure that all executable files (EXE) and Dynamic Link
Libraries (DLL) must use to allow them to be loaded and executed by Windows. PE is
derived from the Microsoft Common Object File Format (COFF). The EXE and DLL
files created using the .NET Framework obey the PE/COFF formats and also add
additional header and data sections to the files that are only used by the CLR. The
specification for the PE/COFF file formats is available at
http://www.microsoft.com/whdc/hwdev/hardware/pecoffdown.mspx

8.What is Event - Delegate?
The event keyword lets you specify a delegate that will be called upon the occurrence of
some "event" in your code. The delegate can have one or more associated methods that
will be called when your code indicates that the event has occurred. An event in one
program can be made available to other programs that target the .NET Framework
Common Language Runtime.// keyword_delegate.cs// delegate declarationdelegate void
MyDelegate(int i);class Program
{
public static void Main()
{
TakesADelegate(new MyDelegate(DelegateFunction));
}
public static void TakesADelegate(MyDelegate SomeFunction)
{
SomeFunction(21);
}
public static void DelegateFunction(int i)
{
System.Console.WriteLine("Called by delegate with number: {0}.", i);
}
}