C# Basics

Question 1

What is the first word in a C# file?

Answer 1

The first word in the file is class.

All code is contained in a class.

Question 2

How many classes can your program have?

Answer 2

As many as you need it to have.

Question 3

How many classes are TYPICALLY in one file?

Answer 3

One.

Question 4

If there is only one class in a file, what should you typically name the file?

Answer 4

The same thing that you named the class within the file.

Question 5

What is a C# file extension?

Answer 5

.cs

Question 6

What element is one step down in the hierarchy from a class that you use to further organize the code?

Answer 6

A method. You can add as many as you need.

Question 7

What are the four basic parts of a method?

Answer 7

Name, body, parameters and type.

Name (of the methoid), body (inside curly braces - this is where you write the instructios), Parameters (info listed next to the method name in parenthesis - used when calling methods , tells other methods what info is needed if you use the method) AND finally TYPE. Tells what kind of info the method will return.

Question 8

What is “calling a method”

Answer 8

You can make one of your methods use (or call upon) another method.

Question 9

What are the three basic building blocks of a C# program?

Answer 9

(in order) Files, classes and methods.

Question 10

How does the compiler know which code to run first in your program?

Answer 10

The file containing the class containing the method named “Main()”

All of the methods you write can be called whatever you want, but one has to be called Main.

Capital M

Question 11

What is a keyword?

Answer 11

Keywords are special words that are reserved for the language itself.

This means that we can’t use them in names of things like classes and methods.

Question 12

What are the 4 P’s of Problem Solving?

Answer 12

First, there’s preparation where we understand the problem and think of a solution.

Second, plan, where we plan out the solution.

Third, perform. Where we perform the actions required for our purposed solution.

And finally, fourth, we perfect the solution.

Perfecting doesn’t mean that the project that the project will be perfect

when we get to the end of the perfecting stage.

Question 13

Which method in the .net framework can be used to print to the console?

Answer 13

System.Console.Write(“”);

Question 14

Which method in the .net framework can be used to read from the console?

Answer 14

System.Console.ReadLine();

What this method does do is return what the user typed back to our program.

Question 15

Variable:

Answer 15

A variable is a way to temporarily store information that our code can use.

Question 16

First step in creating a variable:

Answer 16

Specifying the TYPE of info it needs to store. (e.g. string )

Question 17

Second step in creating a variable:

Answer 17

Give it a name.

Variable names can contain letters, numbers, or an underscore character.
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But they can’t start with a number.
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The name should be descriptive of what it’s meant to store.

Question 18

What is a variable assignment?

Answer 18

Taking a pre-existing declared variable and setting it equal to a value that agrees with its declared type.

Question 19

What does Initializing a variable mean?

Answer 19

Declaring it and assigning in the same line.

aka - string firstName = “Ben”;

instead of

string firstName;
firstName = “Ben”;

Question 20

Disect the following method from the .Net Framework: System.Console.Write

Answer 20

Write is the name of the method.

Console is the name of the CLASS that contains the METHOD “Write” within the framework.

System is the NAMESPACE within the framework. Classes are contained within namespaces.

Question 21

What is the purpose of a namespace?

Answer 21

To make it so that we could potentially have multiple classes with the same name. Think of a namespace as the name of a town and the class is main street.

You cant just send a letter to mainstreet, you have to send it to main street in Grantsville.

Now, if there are multiple “mainstreet” classes in your program, the compiler can distinguish between the Classes “mainStreet” in the namespaces Grantsville and Tooele.

You can use more than one namespace and further organize your library of code.

Question 22

How can you eliminate the use of specific namespaces throughout your file?

Answer 22

Include a “using directive”. Type “using” followed by the name of the namespace. You will then not have to type that out every time.

Question 23

What does the System.Console.WriteLine method from the .Net Framework, do?

Answer 23

It prints text to the console and then brings the cursor to the next line.

This differs from theSystem.Console.Write method because the cursor remains on the same line once that method is called.

Question 24

What is string concatenation?

Answer 24

Adding multiple strings together using the + symbol. (also called the concatenation operator.)

Console.WriteLine(“You’ve entered “ + entry + “ minutes.”);

Question 25

What is a REPL?

Answer 25

Read Evaluate Print Loop

Question 26

What does a REPL do?

Answer 26

Allows you to write a small bit of code and test weather it works or not without having to create a full class or file to go with it. The Mono compiler allows you to do this.

Question 27

How do you use the C# REPL in Mono?

Answer 27

type “csharp>” in the console, this will start the REPL. You can then add your code and test.

Question 28

Why is using a REPL valuable?

Answer 28

It allows you to experiment and learn the language one bit at a time.

Question 29

With the string and int types, which require the value to be enclosed in double quotes?

Answer 29

String does require, quotes are not used with int tho.

Question 30

Interger

Answer 30

In mathematics,
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an integer is a number that can be written without a decimal component.

Question 31

What will happen if you try to add an int with a string?

Answer 31

String concatenation. This may not be the intended result. Be sure to pay attention to data types when trying to either add int values or combine strings with concatenation.

Question 32

Parsing

Answer 32

Extracting data out of text.

Question 33

How can you convert a string to an int?

Answer 33

Parse the int out of the string using int.Parse

Question 34

How do you compile your C# file using the Mono compiler?

Answer 34

In the console, type “mcs “ followed by the name of your .cs file.

Question 35

How do you run your compiled program .exe using Mono?

Answer 35

In the console, type “mono “ followed by the name of the .exe file you wish to run.

Question 36

What is the modulus operator?

Answer 36

% it returns the remainder.

Question 37

What is the order of arithmetic operations in C#?

Answer 37

Same as in regular math. mult, div and modulous first, then add and sub.

If there are multiple div , mult or mod in a row, they will be resolved from left to right.

The highest precidence goes to anything in parenthesis, so you can force specific items to go first.

Question 38

What is a loop?

Answer 38

A loop is used to repeat a section of code until something tells it to stop.

Question 39

How do you turn a block of code into a loop?

Answer 39

while ()
{
   // Your code
}

The code inside your loop will run as long as the parameters set in () remain true.

As soon as they are false, the code immediately following the curly braces will be ran.

Question 40

What is boolean logic?

Answer 40

The idea of a condition being true or false.

Question 41

What is the bool type?

Answer 41

Short for boolean. Can only store true or false. Returns 0 or 1.

Question 42

What is the comparison operator and what does it do?

Answer 42

== it compares two strings against eachother and returns a boolean value. If the thing on the left = the thing on the right, it will return true.

Question 43

What does != do?

Answer 43

Compares if two values are NOT equal and returns T or F`

Question 44

What is the dif between while and if?

Answer 44

Ifs dont loop. They run once.

Question 45

How does a program look at an if statement?

Answer 45

It checks to see if the condition (that you add in () next to if) is true. If it is, it will run the code inside of your if statement. If not, it will move on to the next line.

The condition in your if must resolve to a bool value.

Question 46

How do you include an else to an already declared if statement and how will it run?

Answer 46

You include “else ()
{
}
“

Immediately after the closing } of the if statement that you are working with.

The else will only run if the if returns false.

Question 47

How do you include double quotes into a string? (making sure that the compiler dosent think that the string ends when you add “ ?)

Answer 47

You have to escape the quotes using \ before the “

Question 48

How do you tell a loop to start over at it’s begining from the middle?

Answer 48

With a continue statement.

“continue;”

The loop will start over from its beginning.

Question 49

What is input validation?

Answer 49

A user can type anything they want in the console, but

not everything will make sense to our program so

we need to have some rules about what the program can and can’t accept.

And then enforce those rules somehow.

Question 50

When doing input validation, how do you tell your method to check and see if what the user entered was either a string or an int?

Answer 50

You can use a try catch construct. What this does is sets up two areas. A first area of code to TRY, but if the compiler throws an exeption, it will execute the instructions contained in the CATCH section.

try
{
// All of the code that you want to try but might throw an exeption if the user's input isnt valid.
}
catch(nameOfExeptionBeingThrown)
{
Console.WriteLine("Sorry, you entered something invalid.");
}

Question 51

If you want to make bothj caps and lower case valid input, what is an easy way to do this?

Answer 51

Use the name.ToLower method. So what you would do is compare the user’s input to the input that you are looking for (like the word quit , all lower case) but when you call the user’s input variable name , follow it with .ToLower which will convert all of the characters to lower case and force it to match the input you are looking for. This will make both lower and upper case input valid because it will all end up lower case.

Question 52

What is the data type for decimal numbers?

Answer 52

double

Question 53

What method can you use to have the console tell you what type of data a variable is?

Answer 53

.GetType

Question 54

If an int and a double are combined, what will the resulting data type be?

Answer 54

double

Question 55

What is a cast?

Answer 55

A cast is a way of explicitly informing the compiler that you intend to make the conversion and that you are aware that data loss might occur. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted.

(int)2.9

Question 56

What does it mean to truncate?

Answer 56

Truncate restricts the maximum length of strings. We truncate a string so that it has a substring of the first specified number of letters. This is useful for text in databases or in user interfaces where space is limited.

e.g. (int)2.9 will return 2. The .9 is trunkated.

Question 57

If the result of an arithmetic operation between two ints results in a decimal, what will the result’s data type be?

Answer 57

It will remain an int and be trunkated.

Question 58

What is refactoring code?

Answer 58

Its when you change the code without changing the apparent functionality.

Question 59

Name 6 reasons to refactor your code.

Answer 59

Readability, maintainability, Testability

Performance, extensibility, compliance

Question 60

how do you tell a loop to end?

Answer 60

You use a break statement.

Question 61

What is compile time inference?

Answer 61

It is when you allow the compiler to decide (or infer) the datatype of a variable as its being compiled.

What this means is that instead of specifically declaring a variable’s datatype, you just declare it as a “var” and allow the compiler to look at the data on the right side of the assignment operator to decide for its self what the type is.

var x = 5

int

var y = 6.3 
double

ver z = “hello!”
string

Question 62

What is syntactic sugar?

Answer 62

Its redundant but allows you to shorten the code a bit, making it more readable.

one example would be taking a variable and arithmetically combining it with another variable.

instead of x = x + y, you can do x += y
or
x -= y , x *= y, x /= y, x %= y

Question 63

What will += do?

Answer 63

it will take the var on the left and add its self to the var on the left.