General Technical Questions

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)

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 text in between

some message in between

-----------

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:

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.

///

public class BaseA

{

private BaseA()

{

//

// TODO: Add constructor logic here

//

}

}

Dervied Class:

///

/// Summary description for Class1.

///

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 Main( ) method?

In one .cs file there may be many classes having Main() method. While making the .exe you can define the class name as an entry point

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 Main(), an object, obj, is declared to be of type B.

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

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



courtesy: http://www.crackthecampus.com