General Questions
1. Does C# support multiple-inheritance?
No, use interfaces
instead.
2. When you inherit a protected class-level variable, who is
it available to?
Classes in the same namespace.
3. Are private class-level variables inherited?
Yes, but they
are not accessible. Although they are not visible or accessible via the class interface, they are inherited.
4. Describe the accessibility modifier “protected internal”.
It
is available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared
in).
1. To do: Confirm the “within the same assembly”
portion.
5. C# provides a default class constructor for me. I decide
to write a constructor that takes a string as a parameter, but want to keep the constructor that has no parameter. 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.
6. What’s the top .NET class that everything is derived
from?
System.Object.
7. What does the term immutable mean?
1. answer the question.
8. 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.
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 it’s being operated on,
a new instance 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
first one performs a deep copy of the array, the second one is shallow.
1. To do: improve the answer.
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 class that allows the retrieval of a data element 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# equivalent of C++ catch (…), which was a catch-all statement
for 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 {}.
1. To do: Bad question. Re-word.
17. Can multiple catch blocks be executed?
No. Once the proper catch code fires
off, the control is transferred to the finally block (if there are any), and then whatever follows 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).
19. What is the role of the DataReader class in ADO.NET connections?
It returns a
read-only dataset from the data source when the command is executed.
1. To do: Improve the answer.
Class Questions
20. How do you inherit from a class in C#?
Place a colon and then the name of the
base class.
21. Can you prevent your class from being inherited by another class?
Yes. The
keyword “sealed” will prevent the class from being inherited.
22. 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.
23. 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.
24. When do you absolutely have to declare a class as abstract?
1. When at least one of the methods in the class is abstract.
2. When the class itself is inherited from an abstract class,
but not all base abstract methods have been overridden.
25. What’s an interface class?
It’s an abstract class with public abstract
methods all of which must be implemented in the inherited classes.
26. 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.
1. To do: Clean up this answer.
27. Can you inherit multiple interfaces?
Yes, why not.
1. To do: Need a better answer.
28. 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.
29. What’s the difference between an interface and abstract class?
In an interface
class, all methods must be abstract. In an abstract class some methods can be concrete. In an interface class,
no accessibility modifiers are allowed, which is ok in an abstract class.
30. 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. (questions courtesy of Eyal)
Method and Property Questions
31. What’s the implicit name of the parameter that gets passed into the set method/property
of a class?
value. The data type of the value parameter is defined by whatever data type the property is declared
as.
32. What does the keyword “virtual” declare for a method or property?
The
method or property can be overridden.
33. How is method overriding different from method overloading?
When overriding a
method, you change the behavior of the method for the derived class. Overloading a method simply involves having another
method with the same name within the class.
34. Can you declare an override method to be static if the original method is non-static?
No.
The signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
1. To do: Re-word the answer for better clarity.
35. Can you override private virtual methods?
No. Private methods are not accessible
outside the class.
1. Original answer: No, moreover, you cannot access private
methods in inherited classes, have to be protected in the base class to allow any sort of access.
2. To do: Can a private method even be declared a virtual?
36. What are the different ways a method can be overloaded?
Different parameter data
types, different number of parameters, different order of parameters.
37. If a base class has a number of overloaded constructors, and an inherited class has
a number of overloaded constructors; can you enforce a call from an inherited constructor to a specific 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.
1. To do: question is to complex. It can be stated better.
38. Why is it a bad idea to throw your own exceptions?
Well, if at that point you
know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception
object to the catch block?
Throwing your own exceptions signifies some design flaws in the project.
39. What’s a delegate?
A delegate object encapsulates a reference to a method.
40. What’s a multicast delegate?
It’s a delegate that points to and eventually
fires off several methods.
1. To do: Need a better answer.
Assembly Questions
41. How is the DLL Hell problem solved in .NET?
Assembly versioning allows the
application to specify not only the library it needs to run (which was available under Win32), but also the version of the
assembly.
42. What are the ways to deploy an assembly?
An MSI installer, a CAB archive, and
XCOPY command.
43. What is a satellite assembly?
When you write a multilingual or multi-cultural
application in .NET, and want to
distribute the core application separately from the localized modules,
the localized
assemblies that modify the core application are called satellite assemblies.
44. What namespaces are necessary to create a localized application?
System.Globalization
and System.Resources.
XML Documentation Questions
45. What’s the difference between // comments, /* */ comments and /// comments?
Single-line
comments, multi-line comments, and XML documentation comments.
46. How do you generate documentation from the C# file commented properly with a
command-line
compiler?
Compile it with the /doc switch.
47.What is the difference between and XML documentation tag?
Single line code example and multiple-line
code example.
1. To do: Bad question
48. Is XML case-sensitive?
Yes.
Debugging and Testing Questions
49. What debugging tools come with the .NET SDK?
1. CorDBG – command-line debugger.
To use CorDbg, you
must compile the original C# file using the /debug switch.
2. DbgCLR – graphic debugger. Visual Studio .NET
uses the DbgCLR.
50. What does the “This” window show in the debugger?
It points to the
object that’s pointed to by this reference. Object’s instance data is shown.
1. To do: Need a better answer.
51. What does assert() method do?
In debug compilation, assert takes in a Boolean
condition as a parameter,
and shows the error dialog if the condition is false.
The program proceeds without any interruption
if the condition is true.
52. What’s the difference between the Debug class and Trace class?
Documentation looks the same.
Use Debug class for debug builds,
use Trace class for
both debug and release builds.
53. Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The
tracing dumps can be quite verbose. For applications that are constantly running you run the risk of overloading the
machine and the hard drive. Five levels range from None to Verbose, allowing you to fine-tune the tracing activities.
54. Where is the output of TextWriterTraceListener redirected?
To the Console or a
text file depending on the parameter passed to the constructor.
55. How do you debug an ASP.NET Web application?
Attach the aspnet_wp.exe process to the DbgClr debugger.
56. What are three test cases you should go through in unit testing?
1. Positive test cases (correct data, correct output).
2. Negative test cases (broken or missing data, proper handling).
3. Exception test cases (exceptions are thrown and caught properly).
57. Can you change the value of a variable while debugging a C# application?
Yes. If you are debugging via Visual Studio.NET, just go to Immediate window.
ADO.NET and Database Questions
58. What are advantages and disadvantages of Microsoft-provided data provider classes
in
ADO.NET?
SQLServer.NET data provider is high-speed and robust, but requires SQL Server
license purchased
from Microsoft. OLE-DB.NET is universal for accessing other sources,
like Oracle, DB2, Microsoft Access and Informix.
OLE-DB.NET is a .NET layer on top of
the OLE layer, so it’s not as fastest and efficient as SqlServer.NET.
59. What is the wildcard character in SQL?
Let’s say you want to query database with LIKE for
all employees whose name starts with
La. The wildcard character is %, the proper
query with LIKE would involve ‘La%’.
60. Explain ACID rule of thumb for transactions.
A transaction must be:
1. Atomic - it is one unit of work and does not dependent on
previous and following transactions.
2. Consistent - data is either committed or roll back, no “in-between”
case where something has been updated and something hasn’t.
3. Isolated - no transaction sees the intermediate results of
the current transaction).
4. Durable - the values persist if the data had been committed
even if the system crashes right after.
61. What connections does Microsoft SQL Server support?
Windows Authentication (via
Active Directory) and
SQL Server authentication (via Microsoft SQL Server username and password).
62. Which one is trusted and which one is untrusted?
Windows Authentication is trusted
because the username and password are checked with the Active Directory,
the SQL Server authentication is untrusted, since
SQL Server is the only verifier participating in the transaction.
1. To do: ask the question better.
63. Why would you use untrusted verificaion?
Web Services might use it, as well as
non-Windows applications.
1. To do: answer better.
64. What does the Initial Catalog parameter define in the connection string?
The database
name to connect to.
65. What is the data provider name to connect to an Access database?
Microsoft.Access.
66. What does the Dispose method do with the connection object?
Deletes it from
the memory.
1. To do: answer better. The current answer is not entirely
correct.
67. What is a pre-requisite for connection pooling?
Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security
settings.
The connection string must be identical
What is strong Name ?
A strong name is made up of the full class name including the namespace,
the version
number, culture information (which can be null if culture neutral),
plus a public key and a digital signature.
Satellite Assembly:
Oftenly the satellite assemblies are used to deploy the language-specific
resources for an application. These language-specific
assemblies work in side-by-side
execution because the application has a separate product ID for each language and
installs
satellite assemblies in a language-specific subdirectory for each language.
When uninstalling the application,the application
removes only the satellite assemblies
associated with a given language and .NET Framework version. No core .NET Framework
files
are removed unless the last language for that .NET Framework version is being removed
What is Typed dataset ?
A typed DataSet is
a class that derives from a DataSet. As such,
it inherits all the methods, events, and properties of a DataSet. Typed
DataSet uses
information in the Schema file. Additionally, a typed DataSet provides strongly typed
methods,
events, and properties. This means you can access tables and columns by name,
instead of using collection-based
methods
what is remoting ?
.Net Remoting enables you to build distributed application easily..wheather those
applications
are all in one computer or across some other places...And you can build
client applications that use the other process applications in the same computer or any
other
computer that is reachable in the network.... and also you can communicate with
other domin applications..this is common for
1) Web application
2) Console application
3) Web Services
Remoting servers also can be any type of application domains,
What is fuslogvw.exe?
When the system fails to locate an assembly, it generates a log file.
Fuslogvw.exe is the viewer program that gives you
access to this log. You can run this tool
from a command line. This log information helps you diagnose why the .NET Framework
cannot
locate an assembly at run time.
How to open command prompt through asp.net
System.Diagnostics.Process.Start("cmd.exe");
How Page Postback Works?
In ASP.Net, the Page Load is event is fired every time a page is loaded. This is true even if the page is loaded as part of a submit button click. You may need to identify
if the page load event is called as part of a page submit or if it is a fresh pagerendering. Because,
in case of page submit, you may want to skip several task like populating the data again etc.The
IsPostBack property can be used to determine if the page is submittedto itself. When a form is
posted (submitted) back to the same page that contains it, it's called a post back. ASP.NET provides
a property called IsPostBack that is TRUE when the pageis being loaded as a result of a post back,
and is FALSE otherwise.We can check the value of this proeprty and based on the value, we can populate
the controls in the page. If theproperty is TRUE, that means it is a postback (submit) and no need
to populate all the values again.
