100 Technical Question !!
What is the difference between shadow and override?
Overriding is used to redefines only the
methods.but shadowing redefines the entire element.
You have an event handler called MyEvent and you
want to link the click event of control, MyButton, to use MyEvent, what is the
code that will like them together?
control.Click += new EventHandler(MyEvent)
Which debugging window allows you to see the methods
called in the order they were called?
The call stack.
Which debugging window allows you to see all the
name and values of all the variables in scope?
In Call stack window in MS Visual Studio IDE.
What is wrapper class?is it available in c#?
Wrapper Classes are the classes that wrap up
the primitive values in to a class that offer utility method to access it . For
eg you can store list of int values in a vector class and access the class.
Also the methods are static and hence you can use them without creating an
instance . The values are immutable .
What is protected internal class in C#
Class can be internal not protected or not
even protected internal. Class can have only two access modifiers Public and
internal.if any field or method having access modifier protected internal then
this field available to the others assemblies class and as well as class whose
inharits this class.
Which keyword is used of specify a class that
cannot inherit by other class
By using "sealed" keyword we can
restrict a class from inheritence.
Can u create the instance for abstract classes
No we cannot instanciate abstract class we hav
to extend it first
ex-
abstract class A
{}
class B : A
{}
Class C
{
B b=new B;
}
Can we use Friend Classes or functions in C# the
way we use it in C++
No we can not use friend keyword but instead
c# provide "internal" keyword for friend
How we can use inheritance and polymorphisms in c#
programming?
Inheritance in C# is similar to cpp, if you
are familiar to cpp, the only difference is you dont inherit a class in public
or protected mode, the way to inherit a class is Class Base { protected int
length, breadth; public Base(int a, int b) { this.length = a; this.breadth = b;
} public virtual int Show() { Console.WriteLine(Length of a rectangle is {0}
and breadth is {1}, length, breadth); } } Class Derived: Base // The way to
inherit a class in C# { public Derived(int l, int b, string color): base(l, b)
// call Base constructor { this.color = color; } // an overridden method
beacuse in the derived method we can // change the behaviour, This is a kind on
polymorphism. public override int Show() { base.Show();
Console.WriteLine("Color of the rectangle is " color); } public
string color; } Class Tester { public static void Main() { Base b = new
Base(10, 20); Derived d = new Derived(30, 40, "Red" ); b.Show();
d.show(); } }Output: Length of a rectangle is 10 and breadth is 20 Length of a
rectangle is 30 and breadth is 40 Color of the rectangle is RedI hope this will
make you a bit clear about Inheritance and polymorphism.
How to find exceptions in database
If program successfully complie . but program
is not run or execute.then give an exception.
How can objects be late bound in .NET?
Instead of using new keyword we can use create
object like in this example we are creating object to write in excel sheet
through our programexampleImports Excel = Microsoft.Office.Interop.ExcelPrivate
Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
Handles Button1.Click Dim objApp As Object Dim objBook As Object Dim objBooks
As Object Dim objSheets As Object Dim objSheet As Object Dim range As Object '
Instantiate Excel and start a new workbook. objApp =
CreateObject("Excel.Application") objBooks = objApp.Workbooks objBook
= objBooks.Add objSheets = objBook.Worksheets objSheet = objSheets.Item(1)
range = objSheet.Range("A1") 'Set the range value. range.Value =
"Hello, World!" 'Return control of Excel to the user. objApp.Visible
= True objApp.UserControl = TrueEnd Sub
Where we can use DLL made in C#.Net
Supporting .Net, bcoz DLL made in C#.Net
semicompiled version. Its not a com object. It is used only in .Net
Framework.As it is to be compiled at runtime to byte code.
What Datatypes does the RangeValidator Control
support?
String, Integer, Double, Date, Currency
Constructor is the method which is implicitly
created when ever a class is instantiated. Why?
Constructors are class methods that are
executed when an object of a given type is created. Constructors have the same
name as the class, and usually initialize the data members of the new object
Why multiple Inheritance is not possible in C#?
Multiple Inheritance is possible in C++, but
its not possible in Java, and C#.
what we are read above those are all we know,
but as per my knowledge, in C++ to resolve multiple inheritance we are using
"this pointer". But in C# there is no pointer concept. In such way,
the architectures using the interface concept. To resolving the ambiguity
"this pointer" concept used in c++.
Offcourse it not absolutely correct, but its
my idea only. If you are agree with my view then follow it, else leave it.
Why strings are immutable?
1) In VB6.0 and c++ strings are simple array
of bytes, but in .Net it is class System.String and is immutable.
2) A string is a sequential collection of
Unicode characters, which usually is used to represent text. A String, on the
other hand, is a .NET Framework class (System.String) that represents a Unicode
string with a sequential collection of System.Char structure.
How to convert ocx into DLL
you cannot convert OCX to dll becoz dll do not
have GUI interfaces .IF your ocx does not have GUI and you have convert manuly
by cut and paste from OCX to Dll project
What is the main difference between pointer and
delegate with examples?
A Delegate in c# allows to pass a method of
class to object of other class.
Rules in Deligation:-
1.In order to create a Delegate a
Signature(parameter) must match Signature of object.
2.Define all the methods which has the same
Signature as Deligate define.
3.Create the deligate object & pass the
method as a parameter to Deligate.
4.Now call the encapsulated method using
deligated object.
the best example of Deligation modle is
ADO.NET Architecture & Event Handling in windows environament.
How do i read the information from web.config file?
string
ConStrFromWeb=System.Configuration.ConfigurationSettings.AppSettings["ConStringKey"];
// Here ConStringKey is the key name of
connection string in web.config
What is the default Function arguments?
Default function argument is a function
argument with a default value. Callers of this function have a choice whether
to pass a value for default argument or not. If a function call passes a value
for default argument it is used as its value. If a function call does not pass
a value the default value specified in the function definition is used.
A function may have any number of default arguments.
However all these arguments must follow all mandatory arguments. That is first
you have to specify all non-default or mandatory parameters and then all
default parameters.
What is XML Schema?
Document Type Declaration(DTD)
<!DOCTYPE root-element [ doctype-declaration...
]>
determines the name of the root element and
contains the document type declarations
Elements
Elements are the main building blocks of both
XML and HTML documents.
Examples of HTML elements are "body"
and "table". Examples of XML elements could be "note" and
"message". Elements can contain text, other elements, or be empty.
Examples of empty HTML elements are "hr", "br" and
"img".
Examples:
<body>body text in between</body>
<message>some message in
between</message>
-----------
Attributes
Attributes provide extra information about
elements.
Attributes are always placed inside the
starting tag of an element. Attributes always come in name/value pairs. The
following "img" element has additional information about a source
file:
<img src="computer.gif" />
The name of the element is "img".
The name of the attribute is "src". The value of the attribute is
"computer.gif". Since the element itself is empty it is closed by a
" /".
-----------
Entities
Entities are variables used to define common
text. Entity references are references to entities.
Most of you will know the HTML entity
reference: " ". This "no-breaking-space" entity is used in
HTML to insert an extra space in a document. Entities are expanded when a
document is parsed by an XML parser.
The following entities are predefined in XML:
Entity References Character
< <
> >
& &
" "
' '
How can i check whether a dataset is empty or not
in C#.net
HasRows property is only for DataReader
objects. For DataSet you can check whether it has a DataTable or not .. since
the DataSet is a collection of DataTable you can check whether it has loaded a
table or not using the following code
DataSet dt=new DataSet();
if (dt.Tables.Count>0) // has tables in it
{
}
else // otherwise it is empty
{
}
Is it possible to inherit a class that has
only private constructor?
No.
ex.
Base Class:
/// Summary description for BaseA.
/// </summary>
public class BaseA
{
private BaseA()
{
//
// TODO: Add constructor logic here
//
}
}
Dervied Class:
/// <summary>
/// Summary description for Class1.
/// </summary>
public class DerviedB: BaseA
{
public DerviedB()
{
//
// TODO: Add constructor logic here
//
}
}
Result: DerviedB.cs(10):
'PrivateAssembly.BaseA.BaseA()' is inaccessible due to its protection level
How do you choose 1 entry point when C# project has
more
In one .cs file there may be many classes
having
CSC /main:classname filename.cs
The compiler throws an error if XML comments is not
well formed
If the XML is not well-formed, a warning is
generated and the documentation file will contain a comment saying that an
error was encountered.
By declaring a base class function as virtual we
allow the function to be overridden in subclasses
The derived class can provide new
functionality by overriding the virtual method of the base class.
The method to be called is determined at the
run-time depending on the type of the object calling the method, and it does
not depend on the type of the variable declared to hold the object. The
following example illustrates this point:
Suppose base class B and derived class D
provide different implementations of a virtual method V(). Also suppose that
there is a non-virtual method NV() of B which is overriden by D.
//In
B obj;
//An object of D is created for initializing
obj
obj = new D;
//Call virtual and non-virtual methods on obj:
obj.V(); //This call would execute D::F()
since F() is virtual, and although obj is declared to be of type B, it contains
object of type D.
obj.NV(); //This call would execute B::F(),
looking at the declaration of obj.
This is the difference between virtual and
plain overridable methods. Virtual methods execute slower than non-virtual ones
because of run-time resolve of the method to be called. So programmer should be
caeful while declaring a method as virtual.
Which of the following can not be declared as
virtual
Both A and B are correct choices. Declaring a
static function as virtual generates build error. Same with declaring member
fields as virtual.
A static function can be called only using
class_name.static_function_name() syntax, so there is no run-time resolve
depending on the type of object, hence the term virtual does not make a sense
in case of static functions.
In case member fields are overriden by a
derived class the derived class methods will use the overriden variables by
default, so there is no run-time resolve required for fields.
Sealed class can be inherited
sealed classes cannot be inherited as the
sealed classes provides full functionality only the classes that have no full
functionality can be inherited
Which of the following statements is not true for
interfaces
Interfaces must always be declared as public
so that they can be implemented or inherited
It is not permitted to declare modifier on the
members in an interface definition
A is the correct answer. By default all the
members in an Interface definition are public, so there is no need to declare
access modifier public. It would be a compile time error otherwise
Interface members can not be declared as
Virtual keyword is meaningful when the derived
class is expected to override base class method. Here a class will 'implement'
a method of an interface, hence virtual is not meaningful for interface
methods.
Static keyword indicates that a method or
field is common to all instances of a class. For an interface there will not be
any instance, hence static is not meaningful.
An interface and all its methods must be
declared public for enabling classes to implement them.
Which method is implicitly called when an object is
created
When an object is created Constructor is get
called first. A default constructor is created automatically if we do not
create a constructor inside a class.
Which of the following statement is invalid with
regards to constructor
Constructors should have the same name as class
name
Constructors have to be public so that class
can be instantiated
Constructors can not be overloaded
Constructors can not be static
C# supports two types of constructor, a class
constructor (static constructor) and an instance constructor (non-static
constructor).
Static constructor is used to initialize
static data members as soon as the class is referenced
first time, whereas an instance constructor is
used to create an instance of that class with
<new> keyword. A static constructor does
not take access modifiers or have parameters and can't access any non-static
data member of a class.
Since static constructor is a class
constructor, they are guaranteed to be called as soon as we refer to that class
or by creating an instance of that class.
It is not possible for a delegate to wrap more than
1 methods
False
In some cases you may want to call not just
one, but two or more methods through a single delegate. This is known as
multicasting. You accomplish multicasting by encapsulating the various methods
in delegates, and then you combine the delegates using the Delegate.Combine
shared method. The Combine method takes an array of delegates as a parameter
and returns a new delegate that represents the combination of all the delegates
in the array.
In C# events are actually a special form of
delegates
False
Events are signals generated by an object to
indicate occurrence of an action, while delegates are type safe function
pointers.
An event is a way for a class to signal state
change / an interesting action. Delegates are reference types which are used to
encapsulate methods with a specific signature.
Events are declared using delegates. Objects
which want to take some action on occurrence of the event attach their methods
to the event handler, which is a delegate.
Which preprocessor directive are used to mark that
contain block of code is to be treated as a single block
#Region and #EndRegion indicates a block of
code which can be expanded / collapsed.
How are the attributes specified in C#
They are enclosed with in [].
For performing repeated modification on string
which class is preferred?
StringBuilder class is preferred for
performing repeated operations on string since its value is mutable. String
class represents a text value which is immutable. All operations on string
class which appear to be modifying its value actually return the new value.
So for modifying text contents StringBuilder
class is preferred.
In order to use stringbuilder in our class we need
to refer
We only need to refer System.Text namespace.
StringBuilder Class is contained in the System.Text namespace. hence we need to
add the following lines in pur code:
using System.Text;
Which of the following is not a member of
stringbuilder
Answer is: Dsubstring();
Which method is actually called ultimately when
Console.WriteLine( ) is invoked
AppendFormat() method is called.
What happens when you create an arraylist as
ArrayList Arr=new ArrayList()
Once it will reach size 16 addding element in
the arraylist, it will be automatically double the size.
What is the output of Vectors.RemoveAt(1)
Removes the object at position 1
GetEnumerator( ) of Ienumerable interface returns
GetEnumerator() returns a reference to
System.Collections.Ienumerator class which allows a simple iteration over a
collection
How do you add objects to hashtable
Actually operator "=" adds an
element too.
The following example adds key-value
pair "x"-"value" to
Hashatble h:
HashTable h = new HashTable();
h("x") = "value";
If A.equals(B) is true then A.getHashcode &
B.getHashCode must always return same hash code
The answer is False because it is given that
A.equals(B) returns true i.e. objects are equal and now its hashCode is asked
which is always independent of the fact that whether objects are equal or not.
So, GetHashCode for both of the objects returns different value.
Ans: False
The assembly class is defined in
System.Reflection
What is the first step to do anything with assembly
Load assembly to running process
How do you load assembly to running process
Assembly class provides the following methods
to load an assembly:
Load
LoadFrom
LoadFile
LoadWithPartialName
LoadModule
Assemblies cannot be loaded side by side
This is possible in .net and thats the way DLL
hell is said to be eliminated, its clearly evident from the GAC
Application Isolation is assured using
ApplicationDomain
Where does the version dependencies recorded
Inside an assembly’s manifest
How do you refer parent classes in C#
This keyword is used for reffering current
object and Base keyword is used for referring parrent class. so ans. is C
Which attribute you generally find on top of main
method
[ STAThread ]
How do you make a class not instantiable
Making class as Abstract
In a multilevel hierarchy how are the constructors
are called
TopDown
Always a parent class constructor is executed
before child class' constructor does .. when u instantiate a child/derived
class.
Which utility is used to create resource file
resgen
What is the extension of a resource file
.resx
A shared assembly must have a strong name to
uniquely identify the assembly
True
Public policy applies to
Public policies are applied on Shared
Assemblies.
Stream object can not be initialized
True
Which of the following has stream as the base class
BufferedStream,MemoryStream and FileStream all
these 3 classes are inherited from System.IO.Stream class.
Which class use to Read/Write data to memory
MemoryStream
It is a nonbuffered stream whose encapsulated
data is directly accessible in memory(RAM not files on disk).
To Configure .Net for JIT activation what do you do
Actually JIT activation is required for COM+
components which can be done by setting JustInTimeActivation attribute to true
(choice A). For .net applications / components JIT comes in by default.
Which method is used by COM+ to ascertain whether
class can be pooled
CanBePooled
How do you import Activex component in to .NET
An application called AXImp.exe shipped with
.Net SDK is used.
This application does something similar as
Tlbimp.exe does for non graphical COM components.
It creates a wrapper component that contains
the type information that the .Net runtime can understand.
Net Remoting doesn’t allow creating stateless &
stateful Remote objects
False
Windows services created by C# app run only
Windows NT & Above
What is an indexer in C#
Indexer is a special syntax for overloading []
operator for a class. After defining an indexer, array syntaxes can be used for
the class objects.
In the following cases which is not function
overloading
Same parameter types but different return
values.
Function overloading depends on the
1) parameter types
2) number of parameters
3) order of parameters
How to implement multiple inheritence in C#
Multiple inheritence in C# is achived by using
Interfaces.
In C# a technique used to stream the data is known
as
Serialization
Can static methods be overridable?
No
What is the use of fixed statement
The fixed statement sets a pointer to a
managed variable and "pins" that variable during the execution of
statement.
Without fixed, pointers to managed variables
would be of little use since garbage collection could relocate the variables
unpredictably. (In fact, the C# compiler will not allow you to set a pointer to
a managed variable except in a fixed statement.)
Eg: Class A { public int i; }
A objA = new A; // A is a .net managed type
fixed(int *pt = &objA.i) // use fixed
while using pointers with managed
// variables
{
*pt=45; // in this block use the pointer the
way u want
}
What is the order of destructors called in a
polymorphism hierarchy
Destructors are called in reverse order of
constructors. First destructor of most derived class is called followed by its
parent's destructor and so on till the topmost class in the hierarchy.
You don't have control over when the first
destructor will be called, since it is determined by the garbage collector.
Sometime after the object goes out of scope GC calls the destructor, then its
parent's destructor and so on.
When a program terminates definitely all
object's destructors are called.
How can you sort the elements of the array in
descending order
int[] arr = new int[3];
arr[0] = 4;
arr[1] = 1;
arr[2] = 5;
Array.Sort(arr);
Array.Reverse(arr);
Is it possible to Override Private Virtual methods
No: First of all you cannot declare a method
as 'private virtual'.
What does the volatile modifier do
The system always reads the current value of a
volatile object at the point it is requested, even if the previous instruction
asked for a value from the same object. Also, the value of the object is
written immediately on assignment.
The volatile modifier is usually used for a
field that is accessed by multiple threads without using the lock statement to
serialize access. Using the volatile modifier ensures that one thread retrieves
the most up-to-date value written by another thread.
What is the C# equivalent of System.Single
Float 32 bit
e.g. float i = 6.8F; // or 6.8f
By default, a real numeric literal on the
right-hand side of the assignment operator is treated as double. Therefore, to
initialize a float variable use the suffix f or F.
If you don't use the suffix in the previous
declaration, you will get a compilation error because you are attempting to
store a double value into a float variable.
A single line comments are implemented by
//
Code running under the control of CLR is often
referred as
Managed Code
Platform specific code is obtained when
MSIL code is the intermediate code which is
platform independent.
When MSIL is compiled actual platform
dependent code is generated.
Intermediate Language also facilitates language
interoperability
True
NET interfaces are not derived from IUnknown &
they do not have associated GUID’s
True
Code written in C# can not used in which of the
languages
Java
It is not possible to debug the classes written in
other .Net languages in a C# project.
False: It is definitely possible to debug
other .Net languages code in a C# project. As everyone knows .net can com
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