C# Interview Questions with Answers

Common C# and .net Interview Questions

1. Which of the following methods help us to convert string type data into integers? Select any two. 
A) Convert.toInt32();
B) Convert.Int32();
C) int.parse();
D) parse.int()


2. Suppose you’re implementing a method name “Show” that will be able to take an unlimited number of int arguments. How are you going to define its method signature? 
A) void Show(int[] arg)
B) void Show(params int[] arg)
C) void Show(int a)
D) void Show(ref int a


3. You need to use null-coalescing operator to make sure “name” variable must have a value not null. Select the right way to use null-coalescing operator in C#.
A) string name = n ?? “No Name”;
B) string name = “No Name” ?? null;
C) string name = “No Name” ? null;
D) string name = null ? “No Name”;


4. Which jump statement will you use to start the next iteration while skipping the current iteration of loop?
A) Break
B) Continue
C) Goto
D) Return


5. Which operator is used to compare types? 
A) as
B) is
C) this
D) ?

 

6. Which operator is used to get instance data inside type definition? 
A) as
B) is
C) this
D) ?


7. Which type cannot be instantiated? 
A) enum type
B) static type
C) class type
D) System.Object type


8. The following code is boxed into object 

o. double d = 34.5; 
object o = d;

You’re asked to cast “object o” into “int ”.
A) int i = (int)o;
B) int i = (int)(double)o;
C) int i = (int)(float)(double)o;
D) int i = (float)o;


9. Suppose you’re developing an application which stores a user’s browser history. Which collection class will help to retrieve information of the last visited page?
A) ArrayList
B) Queue
C) Stack
D) HashTable


10. Suppose you’re writing a class that needs a delegate who can refer a method(s) of two input string parameters and return an integer value. Choose the right delegate from the following options.
A) Action<int, string, string>
B) Func<string, string, int>
C) Predicate<int, string, string>
D) EventArgs<int, string, string>



11. You are implementing a method that creates an instance of a class named Person. The Person class contains a public event named Die. The following code segment defines the Die event:

Public event EventHandler Die;

You need to create an event handler for the Die event by using a lambda expression.
A) Person person = new Person();
     person.Die = (s, e) => { /*Method Body*/};
B) Person person = new Person();
     person.Die -= (s, e) => { /*Method Body*/};
C) Person person = new Person();
     person.Die += (s, e) => { /*Method Body*/};
D) Person person = new Person();
      person.Die += () => { /*Method Body*/}



12. Suppose you’re writing a method that has one input string parameter and it returns True if the value of the string input parameter is in upper case. Which of the following delegate(s) will you use to refer this method?
A) Action<bool, string>
B) Func<bool, string>
C) Predicate<string>
D) EventHandler


13. In order to perform a query, a data source must be implemented by: 
A) Enumerable or Queryable
B) Enumerable and Queryable
C) IEnumerable or IQueryable
D) IEnumerable and IQueryable


14. An application includes an object that performs a long-running process. You need to ensure that the garbage collector does not release the object's resources until the process completes.Which garbage collector method should you use?
A) WaitForFullGCComplete()
B) WaitForFullGCApproach()
C) KeepAlive() 
D) WaitForPendingFinalizers()



15. Suppose you're writing an application that uses unmanaged resource. You've implemented an IDisposable interface to manage the memory of unmanaged resource. When implementing Dispose method, which method should you use to prevent garbage collector from calling the object's finalizer? 
A) GC.SuppressFinalize(this)
B) GC.SuppressFinalize(true)
C) GC.WaitForFullGCApproach()
D) GC.WaitForPendingFinalizers()


16. You're instantiating an unmanaged resource; which of the following statements would you use to instantiate an unmanaged resource so that its Dispose method shall always call automatically? 
A) if-else{}
B) try/catch
C) using()
D) switch()


17. Which of the following methods is used to run a LINQ query in parallel? 
A) AsParallel();
B) RunParallel();
C) ToParallel();
D) Parallel();


18. How do you throw an exception to preserve stack-trace information? 
A) throw;
B) throw new Exception();
C) throw e;
D) return new Exception();


19. Suppose you’re developing an application that require that need to define its own custom exceptions. Which of the following class you’d inherit to create a custom exception? 
A) Attribute
B) Exception
C) IEnumerable
D) IEnumerator


20. You are developing an application that retrieves Person type data from the Internet using JSON. You have written the following function for receiving the data so far:

serializer.Deserialize<Person>(json);

Which code segment should you use before this function?
A) DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(Person));
B) DataContractSerializer serializer = new DataContractSerializer(typeof(Person));
C) JavaScriptSerializer serializer = new JavaScriptSerializer();
D) NetDataContractSerializer serializer = new NetDataContractSerializer();


21. You need to store a large amount of data in a file. Which serializer would you consider better?
A) XmlSerializer
B) DataContractSerializer
C) DataContractJsonSerializer
D) BinaryFormatter
E) JavaScriptSerializer


22. You want to serialize data in Binary format but some members don’t need to be serialized. Which attribute should you use?
A) XmlIgnore
B) NotSerialized
C) NonSerialized
D) Ignore 


23. You want to retrieve data from Microsoft Access 2013, which should be read-only. Which class you should use? 
A) SqlDataAdapter
B) DbDataAdapter
C) OleDbDataReader
D) SqlDataReader


24. Suppose you created the ASMX Web Service named SampleService. Which class you would use to create the proxy for this service? 
A) SampleServiceSoapClient
B) SampleService
C) SampleServiceClient
D) SampleServiceSoapProxy
 

25. The application needs to encrypt highly sensitive data. Which algorithm should you use? 
A) DES
B) Aes
C) TripleDES
D) RC2



26. You are developing an application which transmits a large amount of data. You need to ensure the data integrity. Which algorithm should you use? 
A) RSA
B) HMACSHA256
C) Aes
D) RNGCryptoServiceProvider


27. Salt Hashing is done by: 
A) Merging data with random value and perform cryptography.
B) Merging data with random value and perform cryptanalysis.
C) Merging data with random value and perform encryption.
D) Merging data with random value and perform hashing.



28. Which of the following methods is used for getting the information of the current assembly? 
A) Assembly. GetExecutingAssembly();
B) Assembly.GetExecutedAssembly();
C) Assembly.GetCurrentAssembly();
D) Assembly.ExecutingAssembly();



29. Which class should you preferably use for tracing in Release Mode? 
A) Debug
B) Trace
C) TraceSource
D) All of the above


30. Which method is the easiest way of finding the problem if you have no idea what it is? 
A) Using Profiler
B) Profiling by Hand
C) Using Performance Counter
D) Debugging


 Answers:
1: A, C
2. B
3. A
4. B
5. B
6. C
7. B
8. C
9. C
10. B
11. C
12. C
13. C
14. C
15. A
16. C
17. A
18. A
19. B
20. C
21. D
22. C
23. C
24. A
25. B
26. B
27. D
28. A
29. C
30. A