Dot Net -- Questions and Answers[Difference Between] Part-I

Dot Net -- Questions and Answers:[Difference Between]

Part-I

1. What is the difference between public, static and void?

      Public: The keyword public is an access modifier that tells the C# compiler that the Main method is accessible by anyone.

    Static: The keyword static declares that the Main method is a global one and can be called without creating an instance of the class. The compiler stores the address of the method as the entry point and uses this information to begin execution before any objects are created.

Void: The keyword void is a type modifier that states that the Main method does not return any value.

2. What are value types and reference types?

                Value types are stored in the Stack.

Examples: bool, byte, chat, decimal, double, Enum, float, int, long, sbyte, short, strut, uint, ulong, ushort.

Reference types are stored in the Heap.

Examples: class, delegate, interface, object, string.

3. What is the difference between private and public keyword?

                    Private: The private keyword is the default access level and most restrictive among all other access levels. It gives least permission to a type or type member. A private member is accessible only within the body of the class in which it is declared.   

 Public: The public keyword is most liberal among all access levels, with no restrictions to access what so ever. A public member is accessible not only from within, but also from outside, and gives free access to any member declared within the body or outside the body.

4. How is method overriding different from method overloading?

                When overriding a method, you change the behavior of the method for the derived class. Overloading a method simply involves having another method with the same name within the class.

5. 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.

6. What is Authentication and Authorization?

                Authentication is the process of identifying users. Authentication is identifying/validating the user against the credentials (username and password).

Authorization performs after authentication. Authorization is the process of granting access to those users based on identity. Authorization allowing access of specific resource to user.

7. What is difference between constants, read only and, static?

    Constants: The value can’t be changed.

    Read-only: The value will be initialized only once from the constructor of the class.

    Static: Value can be initialized once.

8. What is the difference between string keyword and System? String class?

                String keyword is an alias for System. String class. Therefore, System. String and string keyword are the same, and you can use whichever naming convention you prefer. The String class provides many methods for safely creating, manipulating, and comparing strings.

9. What is the difference between Custom Control and User Control?

                Custom Controls are compiled code (Dlls), easier to use, difficult to create, and can be placed in toolbox. Drag and Drop controls. Attributes can be set visually at design time. Can be used by Multiple Applications (If Shared Dlls), Even if Private can copy to bin directory of web application add reference and use. Normally designed to provide common functionality independent of consuming Application.

User Controls are similar to those of ASP include files, easy to create, cannot be placed in the toolbox and dragged - dropped from it. A User Control is shared among the single application files.

10. What is the difference between break and continue statement?

                The break statement is used to terminate the current enclosing loop or conditional statements in which it appears. We have already used the break statement to come out of switch statements.

The continue statement is used to alter the sequence of execution. Instead of coming out of the loop like the break statement did, they continue statement stops the current iteration and simply returns control back to the top of the loop.

11. What is the difference between static and instance methods?

                A method declared with a static modifier is a static method. A static method does not operate on a specific instance and can only access static members.

A method declared without a static modifier is an instance method. An instance method operates on a specific instance and can access both static and instance members. The instance on which an instance method was invoked can be explicitly accessed as this. It is an error to refer to this in a static method.

12. What is the difference between Array and Arraylist?

                An array is a collection of the same type. The size of the array is fixed in its declaration. A linked list is similar to an array but it doesn’t have a limited size.

13. What is the difference between console and window application?                

    A console application, which is designed to run at the command line with no user interface.

    A Windows application, which is designed to run on a user’s desktop and has a user interface.

14. What is the difference between Array and Linked List?

                Array is a simple sequence of numbers which are not concerned about each others positions. They are independent of each others positions. Adding, removing or modifying any array element is very easy. Compared to arrays, linked list is a complicated sequence of numbers.

15. 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 read only field can be initialized either at the declaration or.

16. What is the main difference between a sub procedure and a function?

                Sub procedures do not return a value, while functions do.

17. How does C# differ from C++?

v  C# does not support #include statement. It uses only using statement.

v  In C# , class definition does not use a semicolon at the end.

v  C# does not support multiple code inheritance.

v  Casting in C# is much safer than in c++.

v  In C# switch can also be used on string values.

v  Command line parameters array behave differently in C# as compared to C++.

18. What is the difference between Shadowing and Overriding?            

   Overriding redefines only the implementation while shadowing redefines the whole element.

    In overriding derived classes can refer the parent class element by using "ME" keyword, but in shadowing you can access it by "MYBASE".

19. What is a basic difference between the while loop and do while loop in C#?

                The while loop tests its condition at the beginning, which means that the enclosed set of

Statements run for zero or more number of times if the condition evaluates to true. The do while loop iterates a set of statements at least once and then checks the condition at the end.

20. What is the main difference between a subprocedure and a function?

                Subprocedures do not return a value, while functions do.

21. What is the difference between an abstract method & virtual method?

                An Abstract method does not provide an implementation and forces overriding to the deriving class (unless the deriving class also an abstract class), where as the virtual method has an implementation and leaves an option to override it in the deriving class. Thus Virtual method has an implementation & provides the derived class with the option of overriding it. Abstract method does not provide an implementation & forces the derived class to override the method.

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22. What are the differences between System. String and System.Text.StringBuilder classes?

System. String is immutable. When we modify the value of a string variable then a new memory is allocated to the new value and the previous memory allocation released. System.StringBuilder was designed to have concept of a mutable string where a variety of operations can be performed without allocation separate memory location for the modified string.

23. What’s the difference between the System.Array.CopyTo () and System.Array.Clone ()?

Using Clone () method, we creates a new array object containing all the elements in the original array and using CopyTo () method, all the elements of existing array copies into another existing array. Both the methods perform a shallow copy.

 24.   What is the difference between Finalize () and Dispose () methods?

Dispose () is called when we want for an object to release any unmanaged resources with them. On the other hand Finalize () is used for the same purpose but it doesn’t assure the garbage collection of an object.

25.   What is difference between is and as operators in c#?

“is” operator is used to check the compatibility of an object with a given type and it returns the result as Boolean.

“as” operator is used for casting of object to a type or a class.

26.   What is difference between the “throw” and “throw ex” in .NET?

“Throw” statement preserves original error stacks whereas “throw ex” has the stack trace from their throw point. It is always advised to use “throw” because it provides more accurate error information.

27.   What is the difference between direct cast and ctype?

Direct Cast is used to convert the type of an object that requires the run-time type to be the same as the specified type in Direct Cast.

Ctype is used for conversion where the conversion is defined between the expression and the type.

28. What’s the difference between and XML documentation tag?

Single line code example and multiple-line code example.

29. What’s the difference between the Debug class and Trace class?

Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.

30.       What is the difference between VB and VB.Net?

Following are the differences between VB and VB.Net:

VB	VB.Net
Platform dependent	Platform Independent
VB is backward compatible	VB.Net is not backward compatible
Interpreted	Compiler Language
Exception Handling by ‘On Error…..Goto’	Exception Handling by ‘Try….Catch’
Cannot develop multi-threaded applications	Can develop multi thread applications

31.       What is the difference between C# and VB.Net?

                Following table gives differences between C# and VB.Net:

VB.Net	C#
Optional Parameters are accepted	Optional Parameters are not accepted
Not case sensitive	Case Sensitive
Nothing is used to release unmanaged resources	‘Using’ is used to release unmanaged resources
Support of Both structured and unstructured error handling	Unstructured error handling

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