Wednesday, September 19, 2012

C sharp basic interview questions and answers for freshers

Can an Interface contain fields?
No, an Interface cannot contain fields.

Can you create an instance of an interface?
No, you cannot create an instance of an interface.

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.

How do you create empty strings in C#?
Using string.empty as shown in the example below.
string EmptyString = string.empty;

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?

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?

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?

14.What class is underneath the SortedList class?
A sorted HashTable.

15.Will the finally block get executed if an exception has not occurred?

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)

1. How many types of JIT compilers are available?
There are Two types of JIT compilers.
standard JIT compiler.
EconoJIT compiler.

2.What are the different types of assemblies – name them?
Satellite assembly

3.What is GAC? What are the steps to be taken to pick up the latest version from GAC?
This Global Assembly Cache(GAC) stores .NET assemblies to be shared by several applications on that computer.publisher policy file is the configuration file to redirect to different version
1. Create the publisher Policy assembly using the assembly linker
2. Add the publisher policy assembly to the GAC using GACutil tool
Gacutil /i
3. During runtime CLR is looking into the publisher policy file and redirect the application to bind with new version assembly as specified inside the publisher policy.

4.How do we use different versions of private assemblies in same application without re-build?
In Asseblyinfo file need specify assembly version.
assembly: AssemblyVersion

5.Different methods of using a legacy COM component in .NET framework?
1. TLBIMP to create an Assembly from a COM component
2. Reference a COM component directly from .NET Editor

6.How do you implement SSL?
1. create certificate request
=>Right click on the website (VD)
=>Click Directory Security Tab and click Server Certificate
=> Type name of certificate , Organization name , server name
location info,
=> Type the path need to save certificate information Submit certificate request.

7.What is ref parameter? What is out parameter?
Ref Parameter: Used to pass a parameter as a reference so that the function called will set the value. This could be used to return more than 1 value by a function.
public int AddMuliply( int a , int b, ref int c)
c = a*b;
return ( a+b);
The above function, returns the addition of two numbers as well as computes the multiplication result and passes to the calling function.
Out Parameter: Used to pass values from the aspx Code-behind to the aspx page.
The difference is that for a ref parameter, you have to assign a value before you call the function, while for OUT parameter, you dont have to assign a value, the calling function assumes that the called function would assign some value.

A ref parameter must first be initialized before being passed from the calling function to the called function. but a out parameter need not be initialized, we can pass it directly when we pass a parameter as ref to a method, the method refers to the same variable and changes made will affect the actual variable.
even the variable passed as out parameter is same as ref parameter, but implementation in c# is different, Arguement passed as ref parameter must be initialized before it is passed to the method. But in case of out parameter it is not necessary. But after a call to a method as out parameter it is necessary to initialize.
When to use out and ref parameter, out parameter is used when we want to return more than one value from a method. Ref parameter can be used as both input and o/p parameter out parameter can be used as only output parameter

8.What is boxing? What is the benefits and disadvantages?
Boxing is converting a value-type to reference type. An example is converting an integer value to an object value.

int intValue = 10;
object obj = (object)intValue;

This is used if you want to pass variables of object types to certain functions or methods you have created. Commonly used in events for example (Object sender...).

9.Why multiple Inheritance is not possible in C#?
Multple inheritance is coneceptually wrong. It shouldn't be allowed in any language. Inheritance is the strongest relationship that can be expressed in OO languages.
It's used to express IS-A relationship. Aggregation is used to express IS CONSTRUCTED IN TERMS OF. If you're using multiple inheritance in C++ then you're design is wrong and you probably want to use aggregation. On the other hand it's plausible to want to use multiple interfaces. For instance you might have a class wheel and a class engine. You could say that your class car inherits from wheel and from engine but that's wrong. In fact car aggregates wheel and engine because it is built in terms of those classes. If wheel is an interface and engine is an interface then car must inherit both of these interfaces since it must implement the functionaity of wheel and engine .On this basis we can see that multiple inheritance for classes should not be allowed because it promotes mis-use of the strong IS-A relationship. C# enforces the correct concepts whilst C++ allows mis-use. multiple interface inheritance is permissible and C# allows this. It's all to do with properly understanding OO concepts.

Absolute Multiple Inheritance is not possible in c# but partially it supports multiple inheritance by the use of Interfaces. As interfaces force a class to implement same type of behaviour (as defined in interface) which classes implements that interface

1 comment:

Adele said...

Tks very much for your post.

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