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1. |
Explain when a type conversion will undergo an implicit
cast and when you must perform an explicit cast. What
are the dangers associated with explicit casts? |
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Types can be implicitly converted when the conversion
can always take place without any potential loss of
data. When a potential loss of data is possible, an
explicit cast is required. If an explicit cast is
improperly performed, a loss of data precision can
result, or an exception can be thrown.
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2. |
Explain why you might use enums and constants instead of
their associated literal values. |
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Enums and constants make code easier to read and
maintain by substituting human-legible tokens for
frequently used constant values.
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3. |
Briefly summarize the similarities and differences
between arrays and collections. |
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Arrays and collections allow you to manage groups of
objects. You can access a particular object by index in
both arrays and collections, and you can use For
Each…Next (foreach) syntax to iterate through the
members of arrays and most collections. Arrays are fixed
in length, and members must be initialized before use.
Members of collections must be declared and initialized
outside of the collection, and then added to the
collection. Collections provided in the
System.Collections namespace can grow or shrink
dynamically, and items can be added or removed at run
time.
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4. |
Explain how properties differ from fields. Why would you
expose public data through properties instead of fields? |
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Properties allow validation code to execute when values
are accessed or changed. This allows you to impose some
measure of control over when and how values are read or
changed. Fields cannot perform validation when being
read or set.
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5. |
Explain what a delegate is and how one works. |
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A delegate acts like a strongly typed function pointer.
Delegates can invoke the methods that they reference
without making explicit calls to those methods.
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6. |
Briefly explain how to convert a string representation
of a number to a numeric type, such as an Integer or a
Double. |
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All numeric data types have a Parse method that accepts
a string parameter and returns the value represented by
that string cast to the appropriate data type. You can
use the Parse method of each data type to convert
strings to that type.
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7. |
What are the two kinds of multidimensional arrays?
Briefly describe each. |
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Multidimensional arrays can be either rectangular arrays
or jagged arrays. A rectangular array can be thought of
as a table, where each row has the same number of
columns. Rectangular arrays with more than two
dimensions continue this concept, where each member of
each dimension has the same number of members of each
other dimension. Jagged arrays can be thought of as an
array of arrays. A two-dimensional jagged array is like
a table where each row might have a different number of
columns.
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8. |
Briefly explain encapsulation and why it is important in
object-oriented programming. |
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Encapsulation is the principle that all of the data and
functionality required by an object be contained by that
object. This allows objects to exist as independent,
interchangeable units of functionality without
maintaining dependencies on other units of code.
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9. |
What is method overloading, and when is it useful? |
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Method overloading allows you to create several methods
with the same name but different signatures. Overloading
is useful when you want to provide the same or similar
functionality to different sets of parameters.
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10. |
You need to create several unrelated classes that each
exposes a common set of methods. Briefly outline a
strategy that will allow these classes to
polymorphically expose that functionality to other
classes. |
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Factor the common set of methods into an interface, and
then implement that interface in each class. Each class
can then be implicitly cast to that interface and can
polymorphically interact with other classes.
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11. |
What is Interface? |
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An interface is a contract. Any object that implements a
given interface guarantees to provide an implementation
of the members defined in that interface. If an object
requires interaction with a specific interface, any
object that implements that interface can supply the
requisite interaction.
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12. |
Describe an abstract class and explain when one might be
useful. |
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An abstract class is a class that cannot be instantiated
but must be inherited. It can contain both implemented
methods and abstract methods, which must be implemented
in an inheriting class. Thus, it can define common
functionality for some methods, a common interface for
other methods, and leave more detailed implementation up
to the inheriting class.
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13. |
What is abstract members? |
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abstract members A member of a base class
that cannot be invoked, but instead provides a
template for members of a derived class. In Visual
Basic .NET, abstract members are declared using the
MustOverride
keyword. In Visual C#, abstract members are declared
using the abstract
keyword.
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14. |
What is base and derived class? |
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base class A class that provides
properties and methods as a foundation for a
derived class. In objected-oriented programming,
one class can be based on another through
inheritance. Using this technique, the base
class provides characteristics (such as
properties and methods) to a derived class. The
derived class can reuse, modify, or add to the
members of the base class
derived class A class that is based on another
class (called a base class) through inheritance.
A derived class inherits the members of its base
class and can override or shadow those members.
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15. |
What is encapsulation ? |
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Encapsulation In component programming, separating the
implementation of a component from the interface. Only
the public interface of a component is made accessible
to the rest of the application. Component data should
never be accessible to outside callers.
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16. |
What is namespace? |
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Namespace A logical
organization of types that perform related functions.
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17. |
What is polymorphism
? |
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Polymorphism The ability of classes to
provide different implementations of the same public
interface. Thus, two classes that exhibit
polymorphism might contain different
implementations, but because the interfaces are
identical, they can be treated the same in code.
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