c# notes

--anonymous class-------------------------
-convenient way of encapsulating read-only properties into a single object without the need to explicitly define a type first.
-use with LINQ
var anAnonymousObject = new { Name = "Tom", Age = 65 };
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--static class---------------------------
-use static class to encapsulate some useful functionality, rather than to represent an instance of anything.
-static class is a class that cannot be instantiated.

-to call a method on a static class, you call the method on the class name itself instead of on an instance name
Conversions.KilosToPounds(weightInKilos);
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--properties------------------------
Auto-implemented properties make property-declaration more concise when creating simple accessor methods (getter and setter). They also enable client code to create objects. When you declare a properties this way, the compiler will automatically create a private, anonymous field in the background that can only be accessed through the get and set accessors.

public string Name { get; set; }

to make a property read-only or write-only only include either the getter or setter

// read only
public string Name { get; }

// write only
public string Name { set; }
--------------------

--structs-------------------------
structs should be small, simple (one-level) collections of related properties, that are immutable once created; for anything else, use a class.

-structs can't derive from any other class or struct type
-structs can't explicitly define a default parameterless constructor
-structs are value types
---------------------

--enums----------

enum Day { Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday };

By default enum values start at 0 and each successive member is increased by a value of 1.  As a result, the previous enum 'Day' would contain the values:

Sunday = 0
Monday = 1
Tuesday = 2

You can change the default by specifying a starting value for your enum as in the following example.

enum Day { Sunday = 1, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday };

// Set an enum variable by name.
Day favoriteDay = Day.Friday;
-------------------------

--arrays---
//declare empty with array size of 10
int[] arrayName = new int[10];

//declare with intilialized values
int[] arrayName = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

//number will contain the value 3
int number = oldNumbers[2];

// Create an array that is 10 long(rows) by 10 wide(columns)
int[ , ] arrayName = new int[10,10];

//multi dimensional
In order to access elements in a multidimensional array, you must include all indices as in the example code here.

// Access the element in the first row and first column
int value = arrayName[0,0]
//Access the element in the first row and second column
int value2 = arrayName[0, 1];
//Access the element in the second row and first column
int value2 = arrayName[1, 0];
-----------------

--indexer example-------------------
public struct Menu
{
    private string[] beverages;
    // This is the indexer.
    public string this[int index]
    {
        get { return this.beverages[index]; }
        set { this.beverages[index] = value; }
    }
    // Enable client code to determine the size of the collection.
    public int Length
    {
        get { return beverages.Length; }
    }
}
----------------------------

--abstract class------
-abstract classes cannot be instantiated
-if employee is the parent class of manager and cashier, it should be abstract because an instance of employee should not exist (only managers and cashiers
-Once you create an abstract class, you decide which methods "must" be implemented in the sub classes and which methods "can" be implemented, or overridden, in the sub class.

-declare methods as virtual if they will be overridden
-declare methods as abstract they must be implemented

An abstract method cannot exist in non-abstract class
An abstract method is not permitted to have any implementation, including curly braces
An abstract method signature must end in a semi-colon
An abstract method MUST be implemented in any sub class.  Failure to do so will generate a compiler warning in C#.

    abstract class Person
        {
            public int Age{get; set;}
            public string Gender{get; set;}

        //set as protected so that its subclasses can use the this constructor to initialize values
            protected Person()
            {
                this.Age = 46;
                this.Gender = "F";
            }
        }

        private class Teacher: Person
        {
        //using base enables the use of the abstract classes defined constructor
            public Teacher(): base()
            {

            }
    }
-------------------------------

--sealed classes------
-sealed classes cannot be inherited
-----------------------------------

--interface--------------
-interface specifies a set of characteristics and behaviors by defining signatures for methods, properties, events, and indexers, without specifying how any of these members are implemented.

-when a class implements an interface, the class provides an implementation for each member of the interface.

-by implementing the interface, the class is thereby guaranteeing that it will provide the functionality specified by the interface.

// Declaring a Class that Implements Multiple Interfaces
public class Coffee: IBeverage, IInventoryItem
{
}

-if need be (like implementing multiple interfaces) you can explicitly implement the interface properties/methods/etc...

// explicitly implementing the IBeverage method IsFairTrade
public bool IBeverage.IsFairTrade { get; set; }

interface polymorphism
// Representing an Object as an Interface Type
Coffee coffee1 = new Coffee();
IBeverage coffee2 = new Coffee();
// implicitly casting to an Interface Type
IBeverage beverage = coffee1;

// Casting an Interface Type to a Derived Class Type
Coffee coffee3 = beverage as Coffee;
// OR
Coffee coffee4 = (Coffee)beverage;
Implementing Multiple Interfaces


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