What are Object Initializers in C#
The Object initializers are the features for programming concepts which was introduced in C#.Net.
The aim of using Object Initializers is to intializing the accessible fields or properties
of an object without the need to write any parameterized constructor or separate
statements.
Sample:
using System;
class Student
{
int rollno;
string stdName;
static void Main()
{
Student s = new Student() { rollno=1,stdName="Ramesh" }; //Object Initializer
}
}
C# interview questions
1 Describe the difference between a Thread and a Process?
2 What is a Windows Service and how does its lifecycle differ from a "standard" EXE?
3 What is the maximum amount of memory any single process on Windows can address? Is this different than the maximum virtual memory for the system? How would this affect a system design?
4 What is the difference between an EXE and a DLL?
5 What is strong-typing versus weak-typing? Which is preferred? Why?
6 Corillian's product is a "Component Container." Name at least 3 component containers that ship now with the Windows Server Family.
7 What is a PID? How is it useful when troubleshooting a system?
8 How many processes can listen on a single TCP/IP port?
9 What is the GAC? What problem does it solve?
10 What is serialization in .NET? What are the ways to control serialization?
11 Does C# support multiple inheritance?
12 What’s the implicit name of the parameter that gets passed into the class’ set method?
13 What’s the top .NET class that everything is derived from?
14 How’s method overriding different from overloading?
15 What is CLR?
16 What is CTS?
17 What is CLS?
18 What is strong name?
19 What is Application Domain?
20 Describe the difference between Interface-oriented, Object-oriented and Aspect-oriented programming.
Events and Delegates in c#
1. What’s a delegate?
A delegate object encapsulates a reference to a method.
2. What’s a multicast delegate?
A delegate that has multiple handlers assigned to it. Each assigned handler (method) is called.
3. What’s the implicit name of the parameter that gets passed into the class’ set method?
Value, and it’s datatype depends on whatever variable we’re changing.
4. How do you inherit from a class in C#?
Place a colon and then the name of the base class.
5. Does C# support multiple inheritance?
No, use interfaces instead.
6. When you inherit a protected class-level variable, who is it available to?
Classes in the same namespace.
7. 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.
8. 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).
9. 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.
10. What’s the top .NET class that everything is derived from?
System.Object.
Class Questions in C#
1.What is the syntax to inherit from a class in C#?
Place a colon and then the name of the base class.
Example: class MyNewClass : MyBaseClass
2.Can you prevent your class from being inherited by another class?
Yes. The keyword “sealed” will prevent the class from being inherited.
3.Can you allow a class to be inherited, but prevent the method from being over-ridden?
Yes. Just leave the class public and make the method sealed.
4.What’s an abstract class?
A class that cannot be instantiated. An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation.
5.When do you absolutely have to declare a class as abstract?
1. When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden.
2. When at least one of the methods in the class is abstract.
6.What is an interface class?
Interfaces, like classes, define a set of properties, methods, and events. But unlike classes, interfaces do not provide implementation. They are implemented by classes, and defined as separate entities from classes.
7.Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public, and are therefore public by default.
8.Can you inherit multiple interfaces?
Yes. .NET does support multiple interfaces.
9.What happens if you inherit multiple interfaces and 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.
10. What’s the difference between an interface and abstract class?
In an interface class, all methods are abstract - there is no implementation. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed. An abstract class may have accessibility modifiers.
11. What is the difference between a Struct and a Class?
Structs are value-type variables and are thus saved on the stack, additional overhead but faster retrieval. Another difference is that structs cannot inherit.
General Questions
1.Does C# support multiple-inheritance?
No. But you can use Interfaces.
2.Where is a protected class-level variable available?
It is available to any sub-class derived from base class
3.Are private class-level variables inherited?
Yes, but they are not accessible.
4.Describe the accessibility modifier “protected internal”.
It is available to classes that are within the same assembly and derived from the specified base class.
6.Which class is at the top of .NET class hierarchy?
System.Object.
7.What does the term immutable mean?
The data value may not be changed.
Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.
8.What’s the difference between System.String and System.Text.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.
9.What’s the advantage of using System.Text.StringBuilder over System.String?
StringBuilder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time a string is changed, a new instance in memory is created.
10.Can you store multiple data types in System.Array?
No.
11.What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array. The CopyTo() method copies the elements into another existing array. Both perform a shallow copy. A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array. A deep copy (which neither of these methods performs) would create a new instance of each element's object, resulting in a different, yet identacle object.
12.How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.
13.What’s the .NET collection class that allows an element to be accessed using a unique key?
HashTable.
14.What class is underneath the SortedList class?
A sorted HashTable.
15.Will the finally block get executed if an exception has not occurred?
Yes.
16.What’s the C# syntax to catch any possible exception?
A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
17.Can multiple catch blocks be executed for a single try statement?
No. Once the proper catch block processed, control is transferred to the finally block .
18.Explain the three services model commonly know as a three-tier application?
Presentation (UI), Business (logic and underlying code) and Data (from storage or other sources).
What are the fundamental differences between value types and reference types?
C# divides types into two categories – value types and reference types. Most of the intrinsic types (e.g. int, char) are value types. Structs are also value types. Reference types include classes, arrays and strings. The basic idea is straightforward – an instance of a value type represents the actual data, whereas an instance of a reference type represents a pointer or reference to the data.The most confusing aspect of this for C++ developers is that C# has predetermined which types are represented as values, and which are represented as references. A C++ developer expects to take responsibility for this decision
Are C# destructors the same as C++ destructors?
No. They look the same but they are very different. The C# destructor syntax (with the familiar ~ character) is just syntactic sugar for an override of the System.Object Finalize method. This Finalize method is called by the garbage collector when it determines that an object is no longer referenced, before it frees the memory associated with the object. So far this sounds like a C++ destructor. The difference is that the garbage collector makes no guarantees about when this procedure happens. Indeed, the algorithm employed by the CLR garbage collector means that it may be a long time after the application has finished with the object. This lack of certainty is often termed ‘non-deterministic finalization’, and it means that C# destructors are not suitable for releasing scarce resources such as database connections, file handles etc.To achieve deterministic destruction, a class must offer a method to be used for the purpose. The standard approach is for the class to implement the IDisposable interface. The user of the object must call the Dispose() method when it has finished with the object. C# offers the ‘using’ construct to make this easier.
