C# Developer Fundamentals Flashcards
Compilation
A special program called a compiler converts your source code into a different format that the computer’s central processing unit (CPU) can execute.
What is the primary job of the compiler?
The compiler primarily converts your code into an executable format that the computer can understand.
You use double quotation marks to create a literal string. True or False?
True!
What is in a web page?
The content, style, and interactive logic are separated into HTML, CSS, and JavaScript files, respectively
Is a fundamental design principle in software development that advocates dividing a system into distinct sections, where each section addresses a specific concern or responsibility. This makes the system more modular, maintainable, and scalable.
Separation of Concerns (SoC)
Key Concept: Concern
Refers to a specific functionality or purpose within a program.
HTML stands for…
Hypertext Markup Language
DOM stands for…
Document Object Model
CSS stands for…
Cascading Style Sheets
CSS rules have entities which are used to express the element (or elements) to which the styles should be applied…
Selector
CSS Selectors Note…
ID and class selectors let you apply styles to custom attribute names in your HTML. You use an ID to style one element, whereas you use classes to style multiple elements.
“.list” is a class or an ID selector?
Class Selector
“#msg” is a class or an ID selector?
ID Selector
Selector that represents the “<html>” element in the HTML page. Used to set global CSS variables (constants) in a CSS rule with the selector.
:root {
–green: #00FF00;
–white: #FFFFFF;
–black: #000000;
}
(or ECMAScript) is a programming language that helps you add interactivity to your web pages.
JavaScript
Is a way to run a JavaScript function when an event happens on the page.
Event handler
JS function that uses CSS selectors, just like the ones you used in your CSS file.
document.querySelector
What is the main purpose of HTML?
HTML is used to provide webpage structure.
In the context of web development, the Console is used for what purpose?
To send debugging messages to a web browser.
Creator of the World Wide Web…
Tim Berners-Lee
SEO stands for…
Search Engine Optimization
ARIA stands for…
Accessible Rich Internet Applications
Alt text for images note
All meaningful images should have an alt attribute (known casually as alt text) to describe what they are or the information that they’re trying to convey.
Images that are purely decorative should have their alt attribute set to an empty string: alt=””.
Is a web development term that means a control can accept input from a keyboard. For example, a button can accept allowing someone to activate or “click” it by selecting the Spacebar.
Focus
What is an appropriate use of ARIA (Accessible Rich Internet Applications) attributes?
ARIA attributes can provide context to a screen reader when you’re creating custom controls that don’t exist natively in HTML.
What is a literal value?
A literal value is a constant value that never changes.
If you want to display a numeric whole number (no fractions) value in the output console, you can use an…
int literal
Is a number that contains a decimal, for example 3.14159.
Floating-point number
C# supports three data types to represent decimal numbers:
+ Float (~6-9 digits)
+ Double (~15-17 digits)
+ Decimal (28-29 digits)
** Each type supports varying degrees of precision.
Tells the compiler you wish to work with a value of float type.
‘F’ literal suffix: Console.WriteLine(0.25F);
In C#, the compiler defaults to which decimal representation?
Double
Tells the compiler you wish to work with a value of Decimal type.
‘m’/’M’ literal suffix: Console.WriteLine(12.39816m);
Recap: C# Data Types
+ string: for words, phrases, or any alphanumeric data for presentation, not calculation.
+ char: for a single alphanumeric character
+ int: for a whole number
+ decimal: for a number with a fractional component
+ bool: for a true/false value
Is literally a hard-coded value.
Literal
Is a container for storing a type of value. Are important because their values can change, or vary, throughout the execution of a program. Can be assigned, read, and changed. Are used to store values that you intend to use in your code.
Variables
How to declare a variable?
To create a new variable, you must first declare the data type of the variable, and then give it a name.
string firstName;
Variable names are case-sensitive in C#?
True
Which is a style of writing variable names?
Camel Case
Is created by using the var keyword followed by a variable initialization. For example:
var message = “Hello world!”;
Implicitly typed local variable
Verbatim String Literal
Use the @ directive to create a verbatim string literal that keeps all whitespace formatting and backslash characters in a string.
> Use the \u plus a four-character code to represent Unicode characters (UTF-16) in a string.
Unicode characters may not print correctly depending on the application.
Unicode characters
String Interpolation
combines multiple values into a single literal string by using a “template” and one or more interpolation expressions.
Interpolation Expressions
Is indicated by an opening and closing curly brace symbol { }. You can put any C# expression that returns a value inside the braces. The literal string becomes a template when it’s prefixed by the $ character.
Example:
string message = $”{greeting} {firstName}!”;
Unicode characters were embedded in the C# strings for a console application to present a greeting message in Thai. However, the message is only displayed as question mark characters. What is a possible cause?
The console in many environments may not support the full range of Unicode characters. As a result, Unicode characters may appear as question marks due to encoding mismatches.
@ symbol
The @ symbol creates a verbatim string where it’s unnecessary to escape the .
‘directory = directory + @”";’
To see division working properly, you need to use a data type that supports fractional digits after the decimal point like…
Decimal
Cast int to decimal
int first = 7;
int second = 5;
decimal quotient = (decimal)first / (decimal)second;
Console.WriteLine(quotient);
Operator that tells you the remainder of int division.
The modulus operator %
The order of operations will follow the rules of the acronym…
PEMDAS:
> Parentheses (whatever is inside the parenthesis is performed first)
> Exponents
> Multiplication and Division (from left to right)
> Addition and Subtraction (from left to right)
Compound Assignment
Operators like +=, -=, *=, ++, and – are known as compound assignment operators because they compound some operation in addition to assigning the result to the variable. The += operator is specifically termed the addition assignment operator.
What does the $ symbol do when used in a string in C#?
The $ symbol allows you to use string interpolation to include variables in the string.
IDE stands for…
Integrated Development Environment
Includes a suite of tools that support the software development process from beginning to end, a process known as the development lifecycle.
Integrated Development Environment (IDE)
.NET SDK
is a cross-platform, open-source developer platform that’s used to develop different types of applications. It includes the software languages and code libraries used to develop .NET applications. You can write .NET applications in C#, F#, or Visual Basic. The .NET platform is used to develop and run applications on Windows, macOS, and Linux. The .NET platform provides a runtime environment for running applications.
.NET runtime
is the code library that’s required to run your C# applications. You may also see the .NET runtime referred to as the Common Language Runtime, or CLR. The .NET runtime isn’t required to write your C# code, but it’s required to actually run your C# applications.
What is the .NET Class Library?
Is a collection of thousands of classes containing tens of thousands of methods. For example, the .NET Class Library includes the Console class for developers working on console applications. The Console class includes methods for input and output operations such as Write(), WriteLine(), Read(), ReadLine(), and many others.
In software development projects, the term state is used to…
Describe the condition of the execution environment at a specific moment in time.
Stateful methods
Are built in such a way that they rely on values stored in memory by previous lines of code that have already been executed. Or they modify the state of the application by updating values or storing new values in memory. They’re also known as instance methods.
what does the following line code do?
Random dice = new Random();
Creates an Object.
creates a new instance of the Random class to create a new object called dice.
A developer creates an instance of the Random class named coins. Which of the following code lines can they use to call the Next() method?
int money = coins.Next();.
This statement uses your instance of the Random class, coins, to return a random number.
Some methods are designed to complete their function and end “quietly”. In other words, they don’t return a value when they finish. They are referred to as…
void methods
Refers to the variable that’s being used inside the method…
Parameter
Is the value that’s passed when the method is called….
Argument
What is an overloaded method?
It is a method that supports several implementations of the method, each with a unique method signature.
Is a collection of one or more lines of code that are defined by an opening and closing curly brace symbol { }. It represents a complete unit of code that has a single purpose in your software system…
Code Block
What is a Boolean statement or expression?
Code that returns either true or false.
Is a collection of individual data elements accessible through a single variable name.
Array
Programming language developed by Microsoft that runs on the .NET Framework…
The first version was released in year 2002. The latest version, C# 13, was released in November 2024.
C# (C-Sharp)
Which keyword most be used to avoid overwrite existing values?
const
Variable type that means unchangeable and read-only…
Constant
Identifiers
unique names for each variable
When you assign a value of one data type to another type, you are…
Type Casting
Converting a smaller type to a larger type size
char -> int -> long -> float -> double
Implicit Casting (automatically)
Converting a larger type to a smaller size type
double -> float -> long -> int -> char
Explicit Casting (manually)
Class has many methods that allows you to perform mathematical tasks on numbers.
Math
Keyword that can save a lot of execution time because it “ignores” the execution of all the rest of the code in the switch block.
break
Keyword that is optional and specifies some code to run if there is no case match in the switch block.
default
Which keyword breaks one iteration (in the loop), if a specified condition occurs, and continues with the next iteration in the loop…
continue
What does ‘static’ means?…
static means that the method belongs to the Program class and not an object of the Program class. You will learn more about objects and how to access methods through objects later in this tutorial.
What does ‘void’ means?…
void means that this method does not have a return value. You will learn more about return values later in this chapter
Multiple methods can have the same name as long as the number and/or type of parameters are different. This is…
Method Overloading
Principle is about reducing the repetition of code. You should extract out the codes that are common for the application, and place them at a single place and reuse them instead of repeating it.
“Don’t Repeat Yourself” (DRY)
Fields and methods inside classes are often referred to as…
Class Members
A static method can be accessed without creating an object of the class?
True
Public methods can only be accessed by…
Objects
Which method type can be accessed without creating an object of the class?
static methods
Which method type can only be accessed by objects?
public methods
Special method that is used to initialize objects, since it is called when an object of a class is created.
Must match the class name
Constructor
Keyword that is an access modifier, which is used to set the access level/visibility for classes, fields, methods and properties.
public
Access modifier that can only be accessed within the same class…
private
Is like a combination of a variable and a method, and it has two methods: a get and a set method…
A property
Is a completely “abstract class”, which can only contain abstract methods and properties (with empty bodies)
An interface
By default, members of an interface are abstract and public….
True
Interfaces can contain properties and methods, but not fields…
True
A special “class” that represents a group of constants (unchangeable/read-only variables).
enum class
It means “specifically listed”
enumerations -> enum
Which class from the System.IO namespace, allows us to work with files?
File class
Which keyword statement allows you to create a custom error?
throw
the initializer, condition, and iterator are…
The for iteration statement conditions
In this variable declaration “string?” what does the character “?” means?
Defines a nullable type variable
jagged array
An array of arrays
Syntax: string[][] jaggedArray = new string[][]
When is it appropriate to use a switch-case construct rather than a if-elseif-else construct?
When more than 2-3 else if code blocks are required, the code can become difficult to read, and the switch-case construct is preferable
Why should a developer choose a for statement rather than a foreach statement when processing the contents of a multidimensional array?
When their code is processing the contents of a multidimensional array, a developer often wants to iterate through the array dimensions separately. The for statement provides better support for processing array dimensions separately.
Why is it important to scope a variable at its lowest necessary level?
Keeping variables scoped at the lowest necessary level enables better resource management and helps to minimize the attack profile of the application.
‘tbd’ stands for…
To Be Determined
Restrict the kinds of values that can be stored in a given variable, which can be helpful when trying to create error free code…
Data Types
Is a free, open-source development framework created by Microsoft that allows developers to build applications for web, mobile, desktop, cloud, gaming, IoT, and AI.
.NET
Data
In software development, data is essentially a value that is stored in the computer’s memory as a series of bits. A bit is a simple binary switch represented as a 0 or 1, or rather, “off” and “on.”
Is a way a programming language defines how much memory to save for a value.
Data Type
Variables that store references to their data (objects), that is they point to data values stored somewhere else….
Reference types
Variables that directly contain their data.
Value types
Uses its bytes to represent an equal number of positive and negative numbers.
Signed types
Uses its bytes to represent only positive numbers.
Unsigned types
A simple value data type that can hold fractional numbers.
floating-point
A value type variable stores its values directly in an area of storage called the…
Stack
(also known as the stack frame, or activation frame)
A reference type variable stores its values in a separate memory region called the…
Heap
Is memory allocated to the code that is currently running on the CPU (also known as the stack frame, or activation frame).
The Stack
Is a memory area that is shared across many applications running on the operating system at the same time.
The Heap
It means that you’re attempting to convert a value from a data type that could hold less information to a data type that can hold more information.
widening conversion
int myInt = 3;
decimal myDecimal = myInt;
It means that you’re attempting to convert a value from a data type that can hold more information to a data type that can hold less information.
narrowing conversion
decimal myDecimal = 3.14m;
int myInt = (int)myDecimal;
Data conversion. ->
Use a Helper Method on the Variable (Instance Method)
int number = 10;
string numberAsString = number.ToString(); // Using instance method
Console.WriteLine(numberAsString); // Output: “10”
Data conversion. ->
Use a Helper Method on the Data Type (Static Method)
Parse() throws an exception if the input is invalid. Use TryParse() for safer conversion:
string invalidStr = “abc”;
bool success = int.TryParse(invalidStr, out int result);
Console.WriteLine(success); // Output: False
Console.WriteLine(result); // Output: 0 (default value)
Data conversion. ->
Use the Convert Class’ Methods
The Convert class provides multiple conversion methods:
string strValue = “42”;
int convertedValue = Convert.ToInt32(strValue);
Console.WriteLine(convertedValue); // Output: 42
When should you use the Convert class?
The Convert class is best for converting fractional numbers into whole numbers (int) because it rounds up the way you would expect.
Which technique results in an error when used to convert a string value “4.123456789” into a decimal?
(decimal)
It isn’t possible to directly cast a string into a decimal and results in an error.
What type of action is being performed when changing a float into an int?
A narrowing conversion.
Which class contains methods that you can use to manipulate the content, arrangement, and size of an array?
Array
What is null?
A value that indicates a variable points to nothing in memory.
Null isn’t the same as an empty string or the value zero.
Uses numbered placeholders within a string. At run time, everything inside the braces is resolved to a value that is also passed in based on their position.
Composite formatting
string first = “Hello”;
string second = “World”;
string result = string.Format(“{0} {1}!”, first, second);
Console.WriteLine(result);
Is a technique that simplifies composite formatting.
Instead of using a numbered token and including the literal value or variable name in a list of arguments to String.Format() or Console.WriteLine(), you can just use the variable name inside of the curly braces.
String interpolation
The :C currency format specifier is used to present the price and discount variables as currency. Update your code as follows:
decimal price = 123.45m;
int discount = 50;
Console.WriteLine($”Price: {price:C} (Save {discount:C})”);
The N numeric format specifier makes numbers more readable. Update your code as follows:
decimal measurement = 123456.78912m;
Console.WriteLine($”Measurement: {measurement:N} units”);
// Measurement: 123,456.79 units
Use the P format specifier to format percentages and rounds to 2 decimal places. Add a number afterwards to control the number of values displayed after the decimal point. Update your code as follows:
decimal tax = .36785m;
Console.WriteLine($”Tax rate: {tax:P2}”);
// Tax rate: 36.79%
Is another version of a method with different or extra arguments that modify the functionality of the method slightly,
overloaded method
What method should be used to search for the first occurrence of a search term in a long string?
IndexOfAny() returns the first position of an array of char that occurs inside of another string.
MVP stands for…
“Minimal Viable Product” (MVP) feature.
A feature that is intended to be a simple working prototype of a feature that enables quick and easy delivery. This feature is not usually a final product, it is intended to help you work through an idea, test it, and gather further requirements.
MVP
Both foreach and for are good choices to iterate small single dimension arrays like {“cat”, “fox”, “dog”, “snake”, “eagle”}, but when is it best to use a for loop?
A for is better when index ranges that aren’t the first to the last index are required.
Given the following method signature, void SetHealth(string health), why don’t operations inside the method affect the original input string health?
Strings can’t be altered once assigned. They can only be overwritten with a new value.
Strings are pass by reference, but they’re immutable and can’t be altered once assigned.
What data type is returned from the following statement: return 100 * 0.5;
A double type
Which type of method doesn’t need to include a return statement?
void methods
What is the purpose of defining an optional parameter in a method?
To simplify the required parameters when a parameter isn’t significant to the result.
What is the purpose of pseudo-code?
Pseudo-code helps to bridge the gap between concept and code.
Exception Handling
Refers to the process that a developer uses to manage those runtime exceptions within their code. Errors that occur during the build process are referred to as errors, and aren’t part of the exception handling process.
Security testing - Performance testing - Usability testing - Compatibility testing
Non-Functional Testing Types
Unit testing - Integration testing - System testing - Acceptance testing are….
Functional Testing Types
What is code debugging?
Code debugging involves isolating and fixing logic issues in code.
What is a debugger?
A debugger is a software tool uses an analytical approach to observe and control the execution flow of a program.
What is the primary benefit of using a debugger?
The primary benefit of using a debugger is watching application code run and following program execution one line of code at a time.
What is one of the most important features of a debugger?
Observation of your program’s state is one of the most important features that come with almost all debuggers.
What is the best way to find the root cause of a bug?
Using a debugger is the best way to find the root cause of a bug.
What is the purpose of catching an exception in C#?
The purpose of catching an exception is to take corrective action when an error occurs.
Can a developer access the contents of an exception at runtime?
Exceptions are objects that can be accessed. The properties of an exception can be used to help determine corrective action.
What happens when execution of a C# application results in a system error?
The .NET runtime throws an exception when a C# application generates a system error.
What is the relationship between the type of exception and the information it contains?
The type of exception determines the information it contains.
What are the namespaces?
Namespaces provide a hierarchical means of organizing C#
programs and libraries. Namespaces contain types and other namespaces.
Those expressions enable you to inspect data and make decisions based on its characteristics…
Pattern Matching
Is an ordered, fixed-length sequence of values with optional names and individual types. You enclose the sequence in ( and ) characters…
Tuples
provide a common syntax to provide collection values. You write values or expressions between [ and ] characters and the compiler converts that expression to the required collection type…
Collection expressions
Provides a common pattern-based syntax to query or
transform any collection of data.
Language integrated query (LINQ)
Unifies the syntax for querying in-memory
collections, structured data like XML or JSON, database storage, and even cloud based
data APIs.
With Language integrated query (LINQ)
Method that is the entry point of a C# application. When the application is started, is the first method that is invoked…
Main Method
When is the StartupObject compiler used for?
If you have more than one class that
has a Main method, you must compile your program with the StartupObject compiler
option to specify which Main method to use as the entry point.
The memory used by an object is reclaimed by the automatic memory management functionality of the CLR, which is known as….
garbage collection
Is a special type of class used for immutable (unchangeable) objects.
A record
Is basically a block of memory that has been allocated
and configured according to the blueprint…
An object
Some methods and properties are meant to be called or accessed from code outside a
class or struct, known as…
Client Code
Types or members are accessible only within files in the same assembly…
Access Modifier: Internal
Is an executable or dynamic link library (DLL) produced from compiling one or more source files.
Assembly
The default accessibility is…
Access Modifier: Private
Is the least permissive access level. Members are accessible only within the body of the class or the struct in which they are declared…
Access Modifier: Private
Namespaces have no access restrictions?
TRUE
Can we change the return type while performing Overriding?
NO, unless the return types are class names
modifier indicates that the thing being modified has a missing or incomplete implementation. ..
Abstract
