C# Object Model Flashcards
- IDE
- UI
- UWP
- XML
- XAML
- Integrated Development Environment
- User Interface
- Universal Windows Platform
- Extensible Markup Language
- Extensible Application Markup Language
Assemblies
- Libraries of compiled code
- Located in the References folder
- //
- (/*) and (*/)
- Comments
- Comments on multiple lines. Opening and closing statements
- using System;
- using System.Collections.Generic;
- using System.Linq;
- using System.Text;
- using System.Threading.Tasks;
Using directives that refer to namespaces
using Windows.UI.Popups;
Contains the MessageDialog class
- Syntax
- Semantics
- Relates to format and construction
- Relates to what statements do
Message Box
Console.WriteLine();
- Assign a value to a float variable
- Assign a value to a long variable
- Assign a value to a decimal variable
- Add F after the value
- Add L after the value
- Add M after the value
- Convert a string value to an integer
- Convert a string value to a double
- Convert a numeric value to a string
- Int.Parse();
- Double.Parse();
- ToString();
String Interpolation
- $”String1 {String2}”
- $”{String1}{String2}”
- Remainder (Modulus) operator
- Not operator
- Equality operator
- And operator
- OR operator
- %
- !
- ==
- &&
- ||
Associativity
- *, / → left to right
- = → right to left
Void
Does not return a value
Cause immediate exit from a void method
Write return; with no expression
Expression-bodied method
- Methods with a single line of code
- Example: void showResult(int answer) => Console.Writeline($”The answer is {answer}”);
C# term for variable defined by a class
Field
In a method, you must declare a variable before you can use it
In a class, you can declare a field can be declared after the statements that require it
Optional parameters
Simply assign them a default value
Short circuiting
- When the first expression of a && statement is false
- When the first expression of a || statement is true
Switch allowed variables
Int, char and string variables
SystemException
- FormatException
- OverflowException
Exception filters
Example:
catch (Exception e) when (e.GetType() != typeof(System.OutOfMemoryException))
Refer to the minimum or maximum value of and int
- int.MinValue
- int.MaxValue
Integer arithmetic overflow checking (int or long)
- checked
- {…
- }
- unchecked
- {…
- }
Throwing an exception
throw new ExceptionType (“Message”)
Create an instance of a class
- Requires the new keyword
- Example:
- Circle c;
- c = new Circle();
Variables declared in a method are not initialized by default
Variables declared in a class are automatically initialized to 0, false or null
Every class must have a constructor
- It must have the same name as the class
- It is public
- It initializes the fields
Partial class
A class that has been split into two files
this keyword
Refers to the field in the object
Static methods
- Can be accessed without creating an instance of the class in which they are contained
- Can not access instance methods or instance fields defined in that same class
- Are available through the lifetime of an application
public static fields
Are shared by all the objects of a class and can be accessed from outside the class
static classes
- Can only contain static members
- Cannot contain any instance data or methods
- Are accessed directly with the name of the class (and not the object as it is usually the case)
using static class name
Allows you to access a static member of a class without specifying the class name
Anonymous class
- Can contain only public fields
- All fields must be initialized and cannot be static
- Example: var name = new { Amount = 108, Message = “string” };
Value types
- int
- float
- double
- char
Reference types
- class
- string
- object
- array
Passing a value type as a parameter
A copy of the variable is made and the original one is unaffected
Passing a reference type as a parameter
The original value of the variable, class or object is modified
Nullable types
- Use ? to declare a nullable value type
- Example: int? i = null;
- Use !i.HasValue to test if the variable is null
Passing a parameter as ref
- Passes the parameter as a reference rather than a copy
- Example:
- name (ref i)
- static void name (ref int i)
Passing a parameter as out
- Passes the parameter as a reference rather than a copy and initializes it
- Example:
- name (out i)
- static void name (out int i)
C# enforces the assignment of values to variables
Variables can’t be read if they have not been initialized
Stack and heap memory
- Stack
- Comes into existence for the execution of a method and is then released
- Contains value types
- Heap
- Comes into existence with the new keyword. Holds objects that are created
- Contains reference types and nullable types
Boxing
- Copying an item from the stack to the heap
- Example:
- int i = 10;
- object x = i;
- Note: if you modify the value on the heap, the value on the stack will not change and vice versa
Cast
- Is used to verify if an object contains the specified variable type
- Example:
- int i = 10;
- object x = i;
- i = (int)x;
is operator
Is used to test if a variable is of a certain type
as operator
- Is used to cast a variable as a certain type
- Example:
- object x = AA
- CustomObject test = x as CustomObject
Enumeration type
- Contains a limited set of symbolic names
- Example:
- enum Season { Spring, Summer, Fall, Winter }
Structure type
- Acts like a class but is stored in the stack
- The compiler always generates a default constructor for structures
How to insert a backslash
(C# assumes that every backslash is the start fo a special character)
- Use two backslash: \
- Put the @ character before the entire string: @”string”
