C# Basics / File I/O / Console App

Question 1

How would you display a line of text in the console?

Answer 1

Console.Write() - to continue on same line Console.WriteLine() - to start new line after displayed

Question 2

What is string interpolation and how is it used?

Answer 2

String interpolation enables you to insert values in string literals to create formatted strings.

Question 3

How would you read a sting literally or verbatim?

Answer 3

@”C:Windows\System32”

Question 4

What is composite formatting of parameters?

Answer 4

{Index [, alignment][:formatString]

Console.WriteLine(“{0,-20} {1,5}\n”, “Name”, “Hours”);

// The example displays the following output:

// Name Hours

Question 5

What is a list?

Answer 5

A list is similar to an array but provides additional functionality, such as dynamic resizing.

Question 6

Define: Index

Answer 6

Index is a number starting from 0 that identifies a corresponding item in the list of objects.

Question 7

Define: Alignment

Answer 7

Alignmet is a signed integer indicating the preferred formatted field width

Question 8

Define: Format string

Answer 8

Format String is a format string that is appropriate for the type of object being formatted

Question 9

What datatypes does C# read from the keyboard?

Answer 9

ONLY STRINGS, unline java, so the need for parsing is often used

Question 10

How would you parse a readline to an integer?

Answer 10

Question 11

What is the other way to convert a sting into an integer?

Answer 11

int myAge = Convert.ToInt32(input)

Question 12

What is the naming convention for methods inside of a class in C#?

Answer 12

Pascal not camel case!

eg. SetName

Question 13

How would you manually create a property to get and set the instance variable?

Answer 13

Question 14

What would a Class diagram look like with a property?

Answer 14

Question 15

How would you manually add validation to a property set method?

Answer 15

Private decimal balance: // instance variabl

Question 16

How would you create an auto-implemented property?

Answer 16

public string Name { get; set; }

Question 17

What is the format specifier for currency and how is it used?

Answer 17

Format Specifier :C

Question 18

What are the main format specifiers?

Answer 18

Question 19

What are the default values for the simple data types in C#?

Answer 19

Types char, byte, sbyte, short, ushort, int, uint, long, ulong, float, double, and decimal are all given the value 0 by default.

Type bool are given a value of false by default.

Reference-type instance variables are of type null by default.

Question 20

What datatype do you use for monetary amounts?

Answer 20

decimal

Question 21

What are the conversion types of datatypes?

Answer 21

Question 22

What is an optional paramater and how is it used?

Answer 22

Methods can have optional parameters that allow the calling method to vary the number of arguments to pass. An optional parameter specifies a default value that’s assigned to the parameter if the optional argument is omitted. You can create methods with one or more optional parameters. All optional parameters must be placed to the right of the method’s non-optional parameters.

eg. static int Power(int baseValue, int exponentValue = 2);

Question 23

What are names parameters and how are they used?

Answer 23

C# provides a feature called named parameters, which enable you to call methods that receive optional parameters by providing only the optional arguments you wish to specify.

Explicitly specify the parameter’s name and value—separated by a colon (:)—in the argument list of the method call.

For example:

// sets the time to 12:00:22

t.SetTime( hour: 12, second: 22 );

The compiler assigns parameter hour the argument 12 and parameter second the argument 22. The parameter minute is not specified, so the compiler assigns it the default value 0.

It’s also possible to specify the arguments out of order when using named parameters. The arguments for the required parameters must always be supplied.

Question 24

What is the new syntax for methods that just return a value?

Answer 24

static int Cube(int x) => x * x * x;

(lambda expressions)

used to be:

static int Cube(int x)

{

return x * x * x;

}

Question 25

How would you use a lambda expression (bodied method) to return true or false?

Answer 25

public bool IsNoFaultState => State == “MA” || State == “NJ” || State == “NY” || State == “PA”;

Question 26

What are the out and ref keywords used for?

Answer 26

Normally functions are passed and return “Values” Meaning that the value passed on if changed does not effect the original variable/number. OUT and REF help pass variables by reference, so if they are passed into another method and changed, the original is changed too becuase its referencing back to the original object.

Question 27

How are the ref and out keywords used?

Answer 27

The out can only send reference out of a method, not pull it in. Ref does both.

eg. out: send objVal 20 in, add objVal 10, send out objVal = 10;
ref: send objVal 20 in, add objVal 10, send out objVal = 20;

Question 28

what does the code for ref keyword look like?

Answer 28

Question 29

what does the code for out keyword look like?

Answer 29

Question 30

How do you create a named constant?

Answer 30

const int ArrayLength = 5;

Question 31

What is a foreach stament and how does it work?

Answer 31

The foreach statement iterates through the elements of an entire array or collection.

Question 32

How would you create a two dimentional rectangular array?

Answer 32

A two-by-two rectangular array b can be declared and initialized with nested array initializers as follows:

int [,] b = {{1, 2}, {3, 4}};

The initializer values are grouped by row in braces. The compiler will generate an error if the number of initializers in each row is not the same, because every row of a rectangular array must have the same number of column

Question 33

How would you create a two dimentional jagged array?

Answer 33

A jagged array with three rows of different lengths could be declared and initialized as follows:

int [][] jagged = {

new int [] {1, 2},

new int [] {3},

new int[] {4, 5, 6}

};

Question 34

How would you create a variable-length argument list?

Answer 34

Variable-length argument lists allow you to create methods that receive an arbitrary number of arguments. The necessary params modifier can occur only in the parameter list’s last parameter.

Question 35

What library is used for the main I/O funcionality?

Answer 35

using System.IO;

Question 36

How do you create a new filestream?

Answer 36

FileStream file = new FileStream(“path.txt”, FileMode , FileAccess );

FileMode specifies what the FileStream should do with the file to begin with

The FileMode.option can be set to one of: Append, Create, CreateNew, Open, OpenOrCreate, or Truncate

FileAccess specifies the file privileges. The FileAccess.option can be set to one of: Read, ReadWrite, or Write

Question 37

How do you write to a file?

Answer 37

StreamWriter data = new StreamWriter(file);

Two options for writing to a file:

Write, or WriteLine data.Write(“Hello file system world!”);

Remember to close the stream when done data.Close();

Question 38

How do you read from a file?

Answer 38

StreamReader data = new StreamReader(file);

Four options for reading from a file:

Read, ReadBlock, ReadLine, or ReadToEnd

string line = data.ReadToEnd();

Remember to close the stream data.Close();

When done with the file make sure to close that as well file.Close();

Question 39

How do you check for the end of a file?

Answer 39

Question 40

How do you view file information?

Answer 40

Question 41

How do you list Disk Drives?

Answer 41

Question 42

How do you list Subfolders?

Answer 42

Question 43

How do you list files?

Answer 43