Types,namespaces,GC

1. What’s the implicit name and type of the parameter that gets passed into the class’ set method?

Value, and it’s data type depends on whatever variable we’re changing.

2. How do you inherit from a class in C#?

Place a colon and then the name of the base class. Notice that it’s double colon in C++.

3. Does C# support multiple inheritance?

No, use interfaces instead.

4. When you inherit a protected class-level variable, who is it available to?

Classes in the same namespace.

5. Are private class-level variables inherited?

Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.

6. Describe the accessibility modifier protected internal. It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).

7. C# provides a default constructor for me. I write a constructor that akes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?

Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.

8. What’s the top .NET class that everything is derived from? System.Object .

9. How’s method overriding different from overloading?

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

10. What does the keyword virtual mean in the method definition? The method can be over-ridden.

11. Can you declare the override method static while the original method is non-static?

No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.

12. Can you override private virtual methods?

No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.

13. Can you prevent your class from being inherited and becoming a base class for some other classes?

Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It’s the same concept as final class in Java.

14. Can you allow class to be inherited, but prevent the method from being over-ridden?

Yes, just leave the class public and make the method sealed.

15. What’s an abstract class?

A class that cannot be instantiated.A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it’s a blueprint for a class without any implementation.

16. When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?

When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.

17. What’s an interface class? It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.

18. Why can’t you specify the accessibility modifier for methods inside the interface?

They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.

19. Can you inherit multiple interfaces?
Yes, why not.

20. And if they have conflicting method names?

It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.

21. What’s the difference between an interface and abstract class?

In the interface all methods must be abstract, in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.

22. How can you overload a method?

Different parameter data types, different number of parameters, different order of parameters.

23. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?

Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.

24. What’s the difference between System. String and System.StringBuilder classes?

System. String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed

25. How big is the data type int in .NET?

32 bits.

26. How big is the char?

16 bits (Unicode).

27. How do you initiate a string without escaping each backslash? Put an @ sign in front of the double-quoted string.

28. What are valid signatures for the Main function? public static void Main () public static int Main () public static void Main ( string[] args ) public static int Main (string[] args )

29. How do you initialize a two-dimensional array that you don’t know the dimensions of? int [ , ] myArray; //declaration myArray = new int [5, 8]; //actual initialization

30. What’s the access level of the visibility type internal? Current application.

31. What’s the difference between struct and class in C#? Structs cannot be inherited. Structs are passed by value, not by reference. Struct is stored on the stack, not the heap.

32. Explain encapsulation. The implementation is hidden, the interface is exposed.

33. What data type should you use if you want an 8-bit value that’s signed? sbyte .

34. Speaking of Boolean data types, what’s different between C# and /C++? There’s no conversion between 0 and false, as well as any other number and true, like in C/C++.

35. Where are the value-type variables allocated in the computer RAM? Stack.

36. Where do the reference-type variables go in the RAM? The references go on the stack, while the objects themselves go on the heap.

37. What is the difference between the value-type variables and reference-type variables in terms of garbage collection? The value-type variables are not garbage-collected, they just fall off the stack when they fall out of scope, the reference-type objects are picked up by GC when their references go null.

38How do you convert a string into an integer in .NET? Int32.Parse( string)

39How do you box a primitive data type variable? Assign it to the object, pass an object.

40Why do you need to box a primitive variable?

To pass it by reference.

41What’s the difference between Java and .NET garbage collectors?

Sun left the implementation of a specific garbage collector up to the JRE developer, so their performance varies widely, depending on whose JRE you’re using. Microsoft standardized on their garbage collection.

42How do you enforce garbage collection in .NET? System.GC.Collect ( );

43.an you declare a C++ type destructor in C# like ~MyClass ()?

Yes, but what’s the point, since it will call Finalize(), and Finalize() has no guarantees when the memory will be cleaned up, plus, it introduces additional load on the garbage collector.

44What’s different about namespace declaration when comparing that to package declaration in Java?
No semicolon.

45What’s the difference between const and read only?

You can initialize read only variables to some runtime values. Let’s say your program uses current date and time as one of the values that won’t change. This way you declare public read only string DateT = new DateTime ().ToString ().

46\a character do?
On most systems, produces a rather annoying beep.

47. Can you create enumerated data types in C#?
Yes.

48. What’s different about switch statements in C#?

No fall-throughs allowed.

49. What happens when you encounter a continue statement inside the for loop?

The code for the rest of the loop is ignored; the control is transferred back to the beginning of the loop.

50. Is goto statement supported in C#? How about Java?

Gotos are supported in C# to the fullest. In Java goto is a reserved keyword that provides absolutely no functionality.