.NET fundamentals 5

What's the difference between const and readonly?
You can initialize readonly variables to some runtime values. Let's say your program uses current date and time as one of the values that won't change. This way you declare public readonly string DateT = new DateTime().ToString().

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.

What's the advantage of using System.Text.StringBuilder over System.String?
StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it's being operated on, a new instance is created.

Can you store multiple data types in System.Array?
No.

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.

How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.

What's the .NET datatype that allows the retrieval of data by a unique key?
HashTable.

What's class SortedList underneath?
A sorted HashTable. 

Will finally block get executed if the exception had not occurred?
Yes.

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.

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.

What's a delegate?
A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.

What's a multicast delegate?
It's a delegate that points to and eventually fires off several methods.

How's 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.

What are the ways to deploy an assembly?
An MSI installer, a CAB archive, and XCOPY command.

What's 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.

What namespaces are necessary to create a localized application?
System.Globalization, System.Resources.

What does assert() 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.

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.

Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.

Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.

What namespaces are necessary to create a localized application?
System.Globalization, System.Resources.

What are three test cases you should go through in unit testing?
Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).

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.

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.

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++.

Does C# support multiple inheritance?
No, use interfaces instead.

When you inherit a protected class-level variable, who is it available to?
Derived Classes.

What's the top .NET class that everything is derived from?
System.Object.

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.

What does the keyword virtual mean in the method definition?
The method can be over-ridden.

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.

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.

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.

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.

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.

Can you inherit multiple interfaces?
Yes.

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.

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.