Basics

Question 1

Define method.

Answer 1

A method performs an action in a series of statements.

Question 2

Define statement block

Answer 2

a pair of braces containing zero or more statements.

Question 3

What is an argument.

Answer 3

An argument is data passed to a method as a parameter.

Question 4

C# recognizes a method called ______ as signaling the default entry point of execution.

Answer 4

Main

static int Main(string[] args) { . . . }

Question 5

List the main types of functions supported by C#.

Answer 5

constructors, methods, operators, properties, events, indexers, and finalizers.

Question 6

At the outermost level of a program, types are organized into _______.

Answer 6

namespaces

The using directive is used to make a namespace available to an application.

Question 7

The C# compiler compiles source code, specifies as a set of files with the .cs extension, into an _______.

Answer 7

assembly.

An assembly is the unit of packing and deployment in .NET and can be either an application or a library.

Question 8

What is the name of the C# compiler?

Answer 8

csc.exe

Question 9

What is an Identifier?

Answer 9

Iderntifiers are names that programmers choose for their classes, methods, variables, and so on.

An identifier must be a whole word, made up of Unicode characters starting with a letter or underscore and are case-sensitive.

Question 10

What is a keyword?

Answer 10

Keywords are names that mean something special to the compiler and are reserved, which means they can not be used as an identifier.

Question 11

List all of the keywords

Answer 11

abstract
as
base
bool
break
byte
case
catch
char
checked
class
const
continue
decimal
default
delegate	do
double
else
enum
event
explicit
extern
false
finally
fixed
float
for
foreach
goto
if
implicit	in
int
interface
internal
is
lock
long
namespace
new
null
object
operator
out
override
params
private	protected
public
readonly
ref
return
sbyte
sealed
short
sizeof
stackalloc
static
string
struct
switch
this
throw	true
try
typeof
uint
ulong
unchecked
unsafe
ushort
using
virtual
void
volatile
while

Question 12

Is it possible to use a keyword as an identifier? If so, how?

Answer 12

It is possible to use a keyword as an identifier by qualifying it with the @ prefix.

Question 13

Is @varName == varName?

Answer 13

The @ symbol doesn’t form part of the identifier itself so @varName is the same as varName.

Question 14

What is a literal?

Answer 14

Literals are primitive pieces of data lexically embedded into the program and also known as fixed values.

It is essentially a language type with an associated value. int dayInMonth = 9;

Question 15

What is a punctuator?

Answer 15

A punctuator help demarcate the structure of a program.Common punctuators include: { } [ ] ‘ “ ;

Question 16

What is an operator?

Answer 16

An operator transforms and combines expressions. Common operators include * / + - % = ( )

Question 17

What is a type?

Answer 17

A type defines the blueprint for a value

Question 18

Which predefined types in C# are value types?

Answer 18

Numeric: - signed integer(sbyte, short, int, long), unsigned integer ( byte, ushort, uint, ulong), real number ( float, double, decimal ); Logical: -bool; Character: - char

Question 19

Which predefined types in C# are reference types?

Answer 19

String & Object

Question 20

List the Numeric suffixes

Answer 20

F   float        float f = 1.0F;
D   double   double d = 1D;
M  decimal   deciimal d = 1.0M;
U   uint          uint = 1U;
L    long        long i = 1L;
UL  ulong       ulong i = 1UL; 

The suffixes U and L are rarely necessary, because the uint, long, and ulong types can nearly always be either inferred or implicitly converted from int.

The F and M suffixes are the most useful and should always be applied when specifying float or decimal literals. Without the F suffix, the following line would not compile, because 4.5 would be inferred to be of type double, which has no implicit conversion to float:

float f = 4.5F;

Question 21

True or False: When using ==, a NaN value is never wqual to another value, even another NaN value:

Answer 21

True

Question 22

List the escape characters

Answer 22

Char	Meaning                  Value
\'	        Single quote	         0x0027
\"	         Double quote	 0x0022
\\	         Backslash	         0x005C
\0	         Null	                 0x0000
\a	         Alert	                 0x0007
\b	         Backspace	         0x0008
\f	         Form feed	         0x000C
\n	         New line	         0x000A
\r	         Carriage return	 0x000D
\t	         Horizontal tab	 0x0009
\v	         Vertical tab             0x000B

Question 23

True or False:

Objects are stored in memory on the Stack and variables/parameters are stored on the Heap.

Answer 23

False:

Variables and parameters are stored on the Stack which grows and shrinks as they these types are allocated and deallocated; while Objects are created on the Heap.

Question 24

Default Values

All type instances have a default value. List them.

Answer 24

Type					Default value
All reference types		null
All numeric types			0
enum types				0
char type				'\0'
bool type				false

Question 25

You can control how parameters are passed with the ref and out modifiers:

Answer 25

Parameter modifier Passed by Variable must be definitely assigned

(None) Value Going in
ref Reference Going in
out Reference Going out

Question 26

True or False:

The out modifier is most commonly used to get multiple values out of a function.

Answer 26

True.

Question 27

From C# 7, you can declare variables on the fly when calling methods with out parameters.

Answer 27

static void Main()
{
Split (“Stevie Ray Vaughan”, out string a, out string b);
Console.WriteLine (a); // Stevie Ray
Console.WriteLine (b); // Vaughan
}

Question 28

What is the null coalescing operator and how does it work?

Answer 28

The ?? operator is the null coalescing operator. It says “If the operand to the left is non-null, give it to me; otherwise, give me a default value.”

For example:

string s1 = null;
string s2 = s1 ?? “nothing”; // s2 evaluates to “nothing”

Question 29

What is the null-conditional operator and how does it work?

Answer 29

The ?. operator is the null-conditional or “Elvis” operator (after the Elvis emoticon), and was introduced in C# 6. It allows you to call methods and access members just like the standard dot operator, except that if the operand on the left is null, the expression evaluates to null instead of throwing a Null​ReferenceException:

System.Text.StringBuilder sb = null;
string s = sb?.ToString(); // No error; s instead evaluates to null