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Explain Virtual Function in C#.

Posted By :Ruchi     Posted Date :February 27, 2009    Points :10   Category :C# 
Virtual functions implement the concept of polymorphism are the same as in C#, except that you use the override keyword with the virtual function implementaion in the child class.

The parent class uses the same virtual keyword. Every class that overrides the virtual method will use the override keyword.

class Shape{
public virtual void Draw()
{ Console.WriteLine("Shape.Draw") ; }
class Rectangle : Shape{
public override void Draw()
{ Console.WriteLine("Rectangle.Draw"); }

You can also find related Interview Question to Explain Virtual Function in C#.  below: 

What is a virtual function ?

virtual function is a function that you want to force derived classes to override. if a class has any overridden pure virtuals, it is an "abstract" class and you can't create objects of that type. (More...)

What's the use of pure virtual function in c#?

The virtual function is used to allow the subclasses to provide implementation for that method using the keyword override.

class MyClass
public void MyMethod()
Console.WriteLine("MyClass.MyMethod is called");
public virtual void MyVirtualMethod()
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what is use of Trim() function and explain different variation ?

Trim function:
remove off Space character from the Beginning and from Ending of the instance.

different Variation in the Trim function:
1)Trim() 2)TrimStart() 3)TrimEnd()

1) Trim():
Simply says, remove off spacing from the Start and End of the Instance or string.
2) TrimStart():
Simply says, Remove off spacing from the Start of the Instance or String
2) TrimEnd():
Simply says, Remove off spacing from the End of the Instance or String

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.
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Define precondition and post-condition to a member function.

A precondition is a condition that must be true on entry to a member function. A class is used correctly if preconditions are never false. An operation is not responsible for doing anything sensible if its precondition fails to hold.
For example, the interface invariants of stack class say nothing about pushing yet another element on a stack that is already full. We say that isful() is a precondition of the push operation.

A post-condition is a condition that must be true on exit from a member function if the precondition was valid on entry to that function. A class is implemented correctly if post-conditions are never false.
For example, after pushing an element on the stack, we know that isempty() must necessarily hold. This is a post-condition of the push operation. (More...)

Explain the concept of Reentrancy?

It is a useful, memory-saving technique for multiprogrammed timesharing systems. A Reentrant Procedure is one in which multiple users can share a single copy of a program during the same period. Reentrancy has 2 key aspects: The program code cannot modify itself, and the local data for each user process must be stored separately. Thus, the permanent part is the code, and the temporary part is the pointer back to the calling program and local variables used by that program. Each execution instance is called activation. It executes the code in the permanent part, but has its own copy of local variables/parameters. The temporary part associated with each activation is the activation record. Generally, the activation record is kept on the stack.

Note: A reentrant procedure can be interrupted and called by an interrupting program, and still execute correctly on returning to the procedure. (More...)

Explain Belady's Anomaly?

Also called FIFO anomaly. Usually, on increasing the number of frames allocated to a process' virtual memory, the process execution is faster, because fewer page faults occur. Sometimes, the reverse happens, i.e., the execution time increases even when more frames are allocated to the process. This is Belady's Anomaly. This is true for certain page reference patterns. (More...)

Difference between a sub and a function.

A Sub Procedure is a method will not return a value
-A sub procedure will be defined with a "Sub" keyword
Sub ShowName(ByVal myName As String)
Console.WriteLine("My name is: " & myName)
End Sub
-A function is a method that will return value(s).
-A function will be defined with a "Function" keyword
Function FindSum(ByVal num1 As Integer, ByVal num2 As Integer) As Integer
Dim sum As Integer = num1 + num2
Return sum
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Explain manifest & metadata.

Manifest is metadata about assemblies. Metadata is machine-readable information about a resource, or ""data about data." In .NET, metadata includes type definitions, version information, external assembly references, and other standardized information. (More...)

Explain the life cycle of an ASP .NET page.

Life cycle of ASP.Net Web Form
Page Request >> Start >> Page Init >> Page Load >> Validation >>
PostBack Event Handling >> Page Rendering >> Page Unload
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whether the page is to be parsed and compiled or a cached verion
of the page is to be sent without running the page.
Start - Page propertied REQUEST and RESPONSE are SET, if the
page is pastback request then the IsPostBack property is SET and
in addition to this UICulture property is also SET.
Page Initilization - In this the UniqueID of each property is SET.
If the request was postback the data is not yet loaded from the
Page Load - If it was a postback request then the data gets loaded
in the control from the ViewState and control property are set.
Validation - If any control validation present, they are performed
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PostBack Event Handling - If it was a postback request then any
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Page Rendering - Before this the viewstate is saved from the page
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What is web application virtual directory?

A virtual directory appears to client browsers as though it were
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Explain manifest & metadata?

Manifest is metadata about assemblies. Metadata is machine-readable information about a resource, or ""data about data." In .NET, metadata includes type definitions, version information, external assembly references, and other standardized information.

Manifest: Manifest describes assembly itself. Assembly Name, version number, culture, strong name, list of all files, Type references, and referenced assemblies.

Metadata: Metadata describes contents in an assembly classes, interfaces, enums, structs, etc., and their containing namespaces, the name of each type, its visibility/scope, its base class, the nterfaces it implemented, its methods and their scope, and each method's parameters, type's properties, and so on.

Shashi Ray (More...)

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