Interview Questions → CSHARP 2.0 → C# 2.0 Questionnaire III

C# 2.0 Questionnaire III

What is the difference between encryption and encoding?

The purpose of encoding is to transform data so that it can be properly (and safely) consumed by a different type of system, e.g. binary data being sent over email. The goal is not to keep information secret, but rather to ensure that it's usable.

The purpose of encryption is to transform data in order to keep it secret from others.

What is composition and aggregation in .Net?

If Inheritance gives us ‘is-a’ relationship then composition gives us ‘part-of’ relationship like if we model a car then Engine is a part of car so that means if life of car ends then life of engine also ends.

public class Engine
{}
public class Car
{
	Engine e= new Engine();
}

Here car manages the life time of engine.

Aggregation gives us ‘has-a’ relationship. Like a person has a address. If the person ceases to exists then address remains. so the life cycle of address is not managed by person.

public class Address
{
}

public class Person
{
  private  Address _PersonAddess;
   public Address  PersonAddess
   {
	    get
	    {
		    return  _PersonAddess;
      }
      set
      {
        _PersonAddess = value;
      }
    }
}

Why concept of interface was introduced?

The concept of interface was introduced to overcome the problems of multiple inheritance of classes. To elaborate let us assume that C# supports multiple inheritance of class.

Consider a class A having a method called ConvertToString() and consider another class B having the method with the same name and signature i.e. ConvertToString().

public class A
{
    public string ConvertToString(Object obj)
    {
        string outputString;
        if (obj == null)
        {
            outputString = Convert.ToString(obj);
        }
        else
        {
            outputString = obj.ToString();
        }
        return outputString;
    }
}
public class B
{
    public string ConvertToString(Object obj)
    {
        return obj.ToString();
    }
}

Now create a third class called C which inherits both class A and class B

public class C : A, B
{
    public void Print()
    {
        //  TODO: Doing some print operation
    }
}

Now let us create the object of class C

C cObj = new C();
Object inputObject;
cObj.ConvertToString(inputObject);

The problem here is which method the class should call the method of class A or B as both classes have different implementations.

This problem was solved by interfaces because when a class inherits an interface then the class have to implement the method whose signature is defined in the interface.

Give examples of runtime and design time polymorphism?

function overloading is an example of design time(or compile time) polymorphism.

Reason - By parsing the method signature and data type the compiler can determine which method to call.

function overriding is an example of runtime polymorphism.

Reason - Consider an example

public class parent
{
  public virtual void Display()
  {
    Console.WriteLine("Parent Class");
    Console.ReadLine();
  }
}
public class child1 : parent
{
}

Now create the object of the class and call the function Display()

parent obj = new child1();
obj.Display();

The output of the program would be "Parent Class". Now change the definition of child1 class.

public class parent
{
  public virtual void Display()
  {
    Console.WriteLine("Parent Class");
    Console.ReadLine();
  }
}

public class child1 : parent
{
  public override void Display()
  {
    Console.WriteLine("child1 Class");
    Console.ReadLine();
  }
}

Now again call function display by creating an instance of an object i.e.

parent obj = new child1();
obj.Display();

The output of the program is "Child1 Class". So in the above example which method is called is determined at runtime i.e. when creating an instance of the object.

What is strong typing and weak typing?

strong typing means placing strong restriction on intermixing of data of different data type.

Consider an C# example

int a = 3;
string b = "2";
string result = string.Concat(a,b);

When the program is compiled error occurs. Because C# doesn't allow the concatenation of an integer and string value.

Consider an example from javascript

<script language="javascript" type="text/javascript">
	var a = 3;
  var b = "2";
  alert(a + b);
</script>

Here an alert will come with value 32. Here javascript is not placing strong restriction on intermixing of data of different data type. So this is weak typing.

What is the difference between First() and FirstOrDefault()?

First() method returns first record, but will throw an exception if there is no record found in the collection whereas FirstOrDefault() method returns first record, but will not throw an exception if there is no record found in the collection

Consider an example

string[] alphabets = { "A", "B", "C", "D", "E", "F" };

string result = (from i in alphabets
                        where i == "G"
                select i).First();

will throw an exception - Sequence contains no elements

string[] alphabets = { "A", "B", "C", "D", "E", "F" };

string result = (from i in alphabets
                        where i == "G"
                select i).FirstOrDefault();

will not throw the exception. If you check the value of result, the value is null.

How to get the difference between 2 dates in terms of day?

Consider the code sample below

DateTime date1 = DateTime.Now.AddHours(-19);
DateTime date2 = DateTime.Now.AddHours(-16);
Console.WriteLine(string.Format("Date2----->{0}{1}", date2, Environment.NewLine));
Console.WriteLine(string.Format("Date1----->{0}{1}", date1, Environment.NewLine));
Console.WriteLine((date2.Date - date1.Date).Days.ToString());

Output -

Date2----->26-11-2012 02:17:30

Date1----->25-11-2012 23:17:30

1

What is the difference between parameters and arguments in .net?

Parameters refers to the variables defined in method definition.

public int Add(int num1, int num2)
{}

Here num1 and num2 are parameters.

Arguments refers to the variables(or values) passed into the method when the method is invoked.

int x = Add (a,b);

Here a and b are arguments.

How to sort data in array?

Using Array.Sort() method

int[] arr = { 2, 4, 5, 1, 6 };
Array.Sort(arr);

How to kill a process from task manager using C#?

Process[] prs = Process.GetProcesses();
foreach(Process pr in prs)
{
	if(pr.ProcessName == "Process_Name")
	pr.Kill();
}

Posted By -

Karan Gupta

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