1. 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++.
2. Does C# support multiple inheritance? No, use interfaces instead.
3. When you inherit a protected class-level variable, who is it available
to? Classes in the
same namespace.
4. 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.
5. 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).
6. C# provides a default constructor for me. I write a constructor
that takes 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.
7. What’s the top .NET class that everything is derived from? System.Object.
8. 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.
9. What does the keyword virtual mean in the method definition? The method can be overridden.
10. 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.
11. 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.
12. 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.
13. 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.
14. 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.
15. 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.
16. What’s an interface class? It’s an abstract
class with public abstract methods all of which
must be implemented in the inherited classes.
17. 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.
18. Can you inherit multiple interfaces? Yes, why not.
19. 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 higherlevel
scale if similarly named methods from different interfaces expect different
data, but as far as
compiler cares you’re okay.
20. 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.
21. How can you overload a method? Different parameter data
types, different number of
parameters, different order of parameters.
22. 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.
23. 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.
24. What’s the difference between struct and class in C#?
1. Structs cannot be inherited.
2. Structs are passed by value, not by reference.
3. Struct is stored on the stack, not the heap.
25. Explain encapsulation. The implementation is hidden, the interface is exposed.
26. Speaking of Boolean data types, what’s different between
C# and C/C++?
There’s no conversion between 0 and false, as well as any other number
and true, like in C/C++.
27. 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.
28. How do you convert a string into an integer in .NET?
Int32.Parse(string),Convert.ToInt32()
29. Can you create enumerated data types in C#? Yes.
30. What’s different about switch statements in C# as compared
to C++?
No fall-throughs allowed.
31. 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.
32. 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.
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