Chapter 4

Question 1

1. To parse a string that might contain a currency value such as $1,234.56, you should pass the Parse or TryParse method which of the following values?
   a. NumberStyles.AllowCurrencySymbol
   b. NumberStyles.AllowThousands
   c. NumberStyles.Currency
   d. A combination of all NumberStyles values

Answer 1

c. NumberStyles.Currency

Question 2

What type does the “checked” block work for and what does it do?

Answer 2

Only for integer. It throws an exception when a narrowing conversion fails.

Question 3

What happens during a narrowing conversion that fails for floats? (Double to float)

Answer 3

The result float is set to infinity. Check for this with float.IsInfinity (static method)

Question 4

Are implicit conversions allowed for narrowing conversions?

Answer 4

No

Question 5

If x were an Int32, what would you get by calling:BitConverter.GetBytes(x)

Answer 5

An array of bytes, 4 actually.

Question 6

How is a cast handled from float to int?

Answer 6

Truncate

Question 7

System.convert.toInt32 does what to a float-to-int conversion?

Answer 7

Rounds to nearest int.

Question 8

Once you cast a reference type to an ancestor class, can you use it again later as the original type?

Answer 8

Yes. It never really changes, it’s a reference (address) after all. You can simply “convert” it back, and no values are lost.

Question 9

Converting to an ancestor class is what kind of conversion? (Widening or narrowing?)

Answer 9

Widening. An explicit cast is required to go the other direction.

Question 10

Will the following code throw?Person person = new Person();Employee employee = (Employee) person;

Answer 10

Yes, the underlying type is actually a Person not an employee.

Question 11

The is operator will returns true for an object if…

Answer 11

The type being checked is in the class hierarchy of the type being tested.

Question 12

What will an as operator return if the types are incompatible.

Answer 12

A null object.

Question 13

What are the three main methods for converting values?

Answer 13

Parsing methodsSystem.ConvertSystem.BitCoverter

Question 14

Parsing methods of conversion only apply to what kind of input and output?

Answer 14

Strings as input and primitive data types as output.

Question 15

How can you get some parsing methods to accept non-numeric characters? Give some examples

Answer 15

System.Globalization.NumberStylesAllowLeadingSignAllowLeadingParenthesisAllowDecimalPoint

Question 16

By default the decimal parser enables what NumberStyles?

Answer 16

Thousands and decimals (points)

Question 17

In C# U.S. formats always apply to what regardless of the locale?

Answer 17

Literal values

Question 18

What kind of rounding does ToIntXX, and ToUIntX use, and how does it work?

Answer 18

Banker’s roundingRound to nearest integer, when tied go with nearest even.

Question 19

How would you do a conversion where you won’t know the type until runtime?

Answer 19

Use Convert.ChangeType(value,type)

Question 20

Once you have an array of bytes can you convert these into integers?

Answer 20

Yes, BitConverter has methods like ToInt

Question 21

Define Boxing and Unboxing

Answer 21

Boxing is converting a value type into an object or an interface that is supported by the value’s type. Unboxing is the converting a boxed value back into its original value.

Question 22

What are the two most common ways to engage interopperability?

Answer 22

COM InteropPlatform Invoke (PInvoke)

Question 23

Helper attribute for PInvoke to help manage data types

Answer 23

MarshallAs

Question 24

When C# does not understand a data type in a dll pulled in using COM, this type helps pacify the compiler.

Answer 24

dynamic type

Question 25

How does the dot net framework store chars?

Answer 25

UTF-16

Question 26

Are c# strings immutable?

Answer 26

Yes. When you think you are manipulating them, they are actually being created and assigned to the reference.

Question 27

Describe the intern pool and how It applies to strings

Answer 27

Each new string created is an entry into the intern pool. The intern pool holds a reference to each unique string. Since strings are I’m unable concatenating strings results in a lot of overhead, as each concatenation involves a new string creation and another entry into the intern pool.

Question 28

What is the purpose of StringBuilder.EnsureCapacity?

Answer 28

To allow the memory allocation up front, instead of having to do it later, essentially twice.

Question 29

A what point does StringBuilder become more efficient than concatenating strings.

Answer 29

Around 7 concatenations.

Question 30

What is the benefit/limitations of StringWriter vs. StringBuilder.

Answer 30

stringWriter is only for appending. It’s faster while StringBuilder is more flexible. Also, StringWriter implements TextWriter.

Question 31

What is StringReader used for.

Answer 31

Reading strings sequentially. Plus StringReader implements TextReader.

Question 32

Can ToString be given formats?

Answer 32

Yes.

Question 33

Standard Numeric Format String: C or c

Answer 33

Currency

Question 34

Standard Numeric Format String: D or d

Answer 34

Decimal (Integer Types only)

Question 35

Standard Numeric Format String: E or e

Answer 35

Scientific Notation

Question 36

Standard Numeric Format String: F or f

Answer 36

Fixed-point

Question 37

Standard Numeric Format String: G or g

Answer 37

General (fixed-point or scientific, whichever is shorter.)

Question 38

Standard Numeric Format String: N or n

Answer 38

Number (with decimal and thousands separators)

Question 39

Standard Numeric Format String: P or p

Answer 39

Percent (multiplied by 100 and % added)

Question 40

Standard Numeric Format String: X or x

Answer 40

Hexadecimal (integer types only)

Question 41

Standard DateTime Format String: d

Answer 41

short date 3/14/2014

Question 42

Standard DateTime Format String: D

Answer 42

Long Date Friday, March 14, 2012

Question 43

Standard DateTime Format String: f

Answer 43

“Full” with short timeFriday, March 14, 2012 2:15 PM

Question 44

Standard DateTime Format String: F

Answer 44

“Full” with long timeFriday, March 14, 2012 2:15:16 PM

Question 45

Standard DateTime Format String: g

Answer 45

“General” with short time3/14/2014 2:15 PM

Question 46

Standard DateTime Format String: G

Answer 46

“General” with longtime3/14/2014 2:15:16 PM

Question 47

Standard DateTime Format String: m or M

Answer 47

Month/Day

Question 48

Standard DateTime Format String: t

Answer 48

short time 2:15 PM

Question 49

Standard DateTime Format String: T

Answer 49

long time 2:15:16 PM

Question 50

Standard DateTime Format String: y or Y

Answer 50

Year/Month March, 2014

Question 51

CLR

Answer 51

Common Language Runtime (CLR) A virtual machine that manages execution of C# (and other .NET) programs.

Question 52

composite format

Answer 52

composite format A format item used by String.Format to indicate how an argument should be formatted. The basic syntax is {index[,length][:formatString]}.

Question 53

immutable

Answer 53

immutable A data type is immutable if its value cannot be changed after it has been created. The String class is immutable. String methods that seem to modify a String, such as Replace and ToUpper, actually replace the String with a new value containing the modified contents.

Question 54

Unicode

Answer 54

Unicode is a standard for encoding characters used by scripts in various locales around the world. It enables a program to display English, Chinese, Kanji, Arabic, Cyrillic, and other character sets. The .NET Framework uses the UTF-16 encoding, which uses 16 bits to represent each character.

Question 55

ToUpper vs ToUpperInvariant?

Answer 55

SomeString.ToUpper will upcase based on the culture that the user is running in.

SomeString.ToUpperInvariant will up-cased based on English but not country based.

Need to say upcase in accordance with some culture.

Question 56

E20. Which of the following methods converts the current date into a string that is appropriate for the user’s locale?

a. DateTime.Now.ToString(“mm/dd/yy”)
b. DateTime.Now.ToString(“D”)
c. DateTime.Now.ToString(“d”)
d. DateTime.Now.ToShortDateString()

Answer 56

b. DateTime.Now.ToString(“D”)
c. DateTime.Now.ToString(“d”)
d. DateTime.Now.ToShortDateString()

Question 57

E19. Which of the following methods formats the variable amount as currency?

a. value.ToString(“C”)
b. value.ToString(“$”)
c. value.ToString(“$#,###.00”)
d. value.ToCurrency()

Answer 57

a. value.ToString(“C”)

Question 58

E18. What purpose does a dynamic data type serve?

a. It enables the program to store more than one kind of data in a variable.
b. It enables the program to convert a value from one type to another automatically without casting.
c. It enables Visual Studio to defer type checking until run time.
d. It prevents type checking.

Answer 58

c. It enables Visual Studio to defer type checking until run time.

Question 59

E17. When working with API functions, a variable with a name that begins with lpsz has what data type?

a. String
b. 32-bit integer
c. Character array
d. Boolean

Answer 59

a. String

Question 60

E16. After executing the following two C# statements, which of the following is true?
int i = 10;
object iObject = i;
a. Variable i holds the value 10.
b. Variable iObject holds the value 10.
c. If you later change the value of iObject, the value of i remains unchanged.
d. All the above.

Answer 60

d. All the above.

Question 61

E15. In the following two statements, where does boxing occur?
int i = 1337;
Console.WriteLine(string.Format(“i is: {0}”, i));
a. Storing 1337 in an int requires that 1337 be boxed.
b. The string.Format method must box its first parameter.
c. The string.Format method must box its second parameter.
d. The Console.WriteLine method must box the result of the string.Format method.

Answer 61

c. The string.Format method must box its second parameter.

Question 62

E14. Which of the following methods converts a 32-bit integer value into an array of bytes?

a. BitConverter.ToBytes
b. BitConverter.GetBytes
c. BitConverter.ToArray
d. ToArray

Answer 62

b. BitConverter.GetBytes

Question 63

E13. Which of the following methods lets you retrieve four 16-bit values that are packed into a 64-byte value returned by an API function?

a. BitConverter.ToInt
b. BitConverter.FromInt64
c. (int)
d. BitConverter.ToInt16

Answer 63

d. BitConverter.ToInt16

Question 64

E12. Which of the following methods does not convert a floating point value into an integer type value?

a. Convert.ChangeType
b. Convert.ToInt16
c. Convert.ToInt32
d. Type.ToInt32

Answer 64

d. Type.ToInt32

Question 65

E11. Which of the following statements correctly casts a float into an int?

a. int value = (float)fvalue
b. int value = (int)fvalue
c. int value = ToInt(fvalue)
d. float value = (int)fvalue

Answer 65

b. int value = (int)fvalue

Question 66

E10. Which of the following string methods combines an array of values into a single delimited string?

a. FromArray
b. Fields
c. Join
d. Merge

Answer 66

c. Join

Question 67

E9. Which of the following string methods breaks a delimited string into pieces?

a. ToArray
b. Split
c. Fields
d. Join

Answer 67

b. Split

Question 68

E8. Which of the following methods enables a program to parse an integer entered in a TextBox by the user?

a. int.Parse
b. int.TryParse
c. string.Parse
d. string.ParseInt
e. System.Convert.ToInt32

Answer 68

a. int.Parse
b. int.TryParse

e. System.Convert.ToInt32

Question 69

E7. Suppose the Customer class inherits from the Person class, cust is a Customer variable that holds a reference to a Customer object, and person is a Person variable that holds a reference to a Person object. Then which of the following statements will fail at run time?

a. cust = person;
b. cust = person as Customer;
c. cust = (Customer)person;
d. person = cust;
e. person = cust as Person;
f. person = (Person)cust;

Answer 69

c. cust = (Customer)person;

Question 70

E6. Suppose the Customer class inherits from the Person class, cust is a Customer variable that holds a reference to a Customer object, and person is a Person variable that holds a reference to a Person object. Then which of the following statements will fail at design time?

a. cust = person;
b. cust = person as Customer;
c. cust = (Customer)person;
d. person = cust;
e. person = cust as Person;
f. person = (Person)cust;

Answer 70

a. cust = person;

Question 71

E5. During which of the following conversions might there be a loss of precision?

a. Converting an int to a float
b. Converting a float to a long
c. Converting a long to an int
d. Converting an int to a long
e. Converting a float to a decimal
f. Converting a decimal to a float

Answer 71

a. Converting an int to a float
b. Converting a float to a long

e. Converting a float to a decimal
f. Converting a decimal to a float

Question 72

E4. If the Manager class inherits from the Employee class, and the Employee and Customer classes both inherit from the Person class, then which of the following are widening conversions?

a. Converting a Person to a Manager
b. Converting an Employee to a Manager
c. Converting an Employee to a Person
d. Converting a Manager to a Person
e. Converting a Manager to an Employee
f. Converting a Person to an Employee
g. Converting a Customer to an Employee
h. Converting an Employee to a Customer

Answer 72

c. Converting an Employee to a Person
d. Converting a Manager to a Person
e. Converting a Manager to an Employee

Question 73

E3. If the Manager class inherits from the Employee class, and the Employee and Customer classes both inherit from the Person class, then which of the following are narrowing conversions?

a. Converting a Person to a Manager
b. Converting an Employee to a Manager
c. Converting an Employee to a Person
d. Converting a Manager to a Person
e. Converting a Manager to an Employee
f. Converting a Person to an Employee
g. Converting a Customer to an Employee
h. Converting an Employee to a Customer

Answer 73

a. Converting a Person to a Manager
b. Converting an Employee to a Manager

f. Converting a Person to an Employee

(In a sense you could technically consider g and h to be considered narrowing conversions, but actually they are just invalid conversions.)

Question 74

E2. Which of the following are widening conversions?

a. Converting a byte to an integer
b. Converting a double to a float
c. Converting an integer to a long
d. Converting a float to a double
e. Converting an integer to a float
f. Converting a double to a long
g. Converting a decimal to an integer
h. Converting an integer to a decimal

Answer 74

a. Converting a byte to an integer

c. Converting an integer to a long
d. Converting a float to a double
e. Converting an integer to a float

h. Converting an integer to a decimal

Question 75

E1. Which of the following are narrowing conversions?

a. Converting a byte to an integer
b. Converting a double to a float
c. Converting an integer to a long
d. Converting a float to a double
e. Converting an integer to a float
f. Converting a double to a long
g. Converting a decimal to an integer
h. Converting an integer to a decimal

Answer 75

b. Converting a double to a float

f. Converting a double to a long
g. Converting a decimal to an integer

Question 76

13. Which of the following techniques should you use to watch for floating point operations that cause overflow or underflow?
    a. Use a checked block.
    b. Use a try-catch block.
    c. Check the result for the value Infinity or NegativeInfinity.
    d. Check the result for Error.

Answer 76

c. Check the result for the value Infinity or NegativeInfinity.

Question 77

12. Which of the following statements can you use to catch integer overflow and underflow errors?
    a. checked
    b. overflow
    c. watch
    d. try

Answer 77

a. checked

Question 78

11. Which of the following techniques does not create a String containing 10 spaces?
    a. Set a String variable equal to a literal containing 10 spaces.
    b. Use a String constructor passing it an array of 10 space characters.
    c. Use a String constructor passing it the space character and 10 as the number of times it should be repeated.
    d. Use the String class’s Space method passing it 10 as the number of spaces the string should contain.

Answer 78

d. Use the String class’s Space method passing it 10 as the number of spaces the string should contain.

Question 79

10. Which of the following is not a String method?
    a. IndexOf
    b. StartsWith
    c. StopsWith
    d. Trim

Answer 79

c. StopsWith

Question 80

9. If Employee inherits from Person and Manager inherits from Employee, which of the following statements is valid?
   a. Person alice = new Employee();
   b. Employee bob = new Person();
   c. Manager cindy = new Employee();
   d. Manager dan = (Manager)
   (new Employee());

Answer 80

a. Person alice = new Employee();

Question 81

8. The statement object obj = 72 is an example of which of the following?
   a. Explicit conversion
   b. Immutable conversion
   c. Boxing
   d. Unboxing

Answer 81

c. Boxing

Question 82

7. Which of the following methods is the best way to store an integer value typed by the user in a variable?
   a. ToString
   b. Convert
   c. ParseInt
   d. TryParse

Answer 82

d. TryParse

Question 83

6. If i is an int and l is a long, which of the following statements is true?
   a. i = (int)l is a narrowing conversion.
   b. l = (long)i is a narrowing conversion.
   c. l = (long)i could cause an integer overflow.
   d. The correct way to copy i’s value into l is
   l = long.Parse(i).

Answer 83

a. i = (int)l is a narrowing conversion.

Question 84

5. Which of the following statements generates a string containing the text “Veni, vidi, vici”?
   a. String.Format(“{0}, {1}, {2}”,
   Veni, vidi, vici)
   b. String.Format(“{1}, {2}, {3}”,
   “Veni”, “vidi”, “vici”)
   c. String.Format(“{2}, {0}, {3}”,
   “vidi”, “Venti”, “Veni”, “vici”)
   d. String.Format(“{Veni, vidi, vici}”)

Answer 84

c. String.Format(“{2}, {0}, {3}”,

“vidi”, “Venti”, “Veni”, “vici”)

Question 85

4. Assuming total is a decimal variable holding the value 1234.56, which of the following statements displays total with the currency format $1,234.56?
   a. Console.WriteLine(total.ToString());
   b. Console.WriteLine(total.ToCurrency
   String());
   c. Console.WriteLine(total.ToString
   (“c”));
   d. Console.WriteLine(Format(“{0:C}”,
   total);

Answer 85

c. Console.WriteLine(total.ToString

(“c”));

Question 86

3. Which of the following statements is true for narrowing conversions?
   vThe conversion will not result in loss of magnitude but may result is some loss of precision.
   b. The source and destination types must be compatible.
   c. An explicit cast is optional.
   d. A cast can convert a string into an int if the string holds numeric text.

Answer 86

b. The source and destination types must be compatible.

Question 87

2. Which of the following statements is true for widening conversions?
   a. Any value in the source type can fit into the destination type.
   b. The conversion will not result in loss of magnitude but may result is some loss of precision.
   c. An explicit cast is optional.
   d. All of the above.

Answer 87

d. All of the above.