private static void classesAndObjects()
{
// All classes descend from object
var x = new object();
Console.WriteLine($"Type of x {x.GetType()}");
Console.WriteLine($"x is object {x is object}");
var number = new MyNumber()
{
Value = 3
};
Console.WriteLine($"Type of number {number.GetType()}");
Console.WriteLine($"number is object {number is object}");
// Note even though didn't explcitly declare MyNumber as inheriting from object it's inferred
// Casting, can cast to any ancestor type in the inheritance
object numberasobject = (object)number;
Console.WriteLine($"Type of numberasobject {numberasobject.GetType()}");
Console.WriteLine($"numberasobject is object {numberasobject is object}");
// So casting doesn't create a new object
// If we have the following OO classes Animal -> Cat : Animal (i.e. Cat inherits from Animal)
// Various language can be used, such as:
//
// Animal is the supertype Cat is the sub type
// Cat inherits from Animal
// Cat extends Animal
// Animal is the parent of Cat
// Animal is the base pof Cat
//
// When casting we can only cast up the chain i.e. from a subtype to a supertype
}
private static void valueVsReferenceTypes()
{
int x = 3; //000000...11
int y = 3;
bool result = (x == y);
Console.WriteLine($"x == y: {result}");
x = 4; //0000000...100
result = (x == y);
Console.WriteLine($"x (changed) == y: {result}");
MyNumber number1 = new MyNumber()
{
Value = 3
};
MyNumber number2 = new MyNumber()
{
Value = 3
};
result = (number1.Value == number2.Value);
Console.WriteLine($"number1.Value == number2.Value: {result}");
result = (number1 == number2);
Console.WriteLine($"number1 == number2: {result}");
MyNumber number3 = new MyNumber()
{
Value = 3
};
MyNumber number4 = number3;
result = (number3 == number4);
Console.WriteLine($"number3 == number4: {result}");
number3.Value = 4;
result = (number3 == number4);
Console.WriteLine($"Again, number3 == number4: {result}");
number3 = new MyNumber()
{
Value = 4
};
result = (number3 == number4);
Console.WriteLine($"Yet again, number3 == number4: {result}");
result = (number3.Value == number4.Value);
Console.WriteLine($"number3.Value == number4.Value: {result}");
// Value types (abridged): bool, int, char, enum long, decimal
// Reference types: array, string, class, delegate
//// Parameter passing
int intof3 = 3;
var intresult = addOneToInt(intof3);
result = intresult == intof3;
Console.WriteLine($"result = {result}, intresult = {intresult}, intof3 = {intof3}");
MyNumber numberof3 = new MyNumber()
{
Value = 3
};
int numberresult = addOneToClassInstance(numberof3);
result = numberresult == numberof3.Value;
Console.WriteLine($"result = {result}, numberresult = {numberresult}, numberof3.Value = {numberof3.Value}");
intof3 = 3;
intresult = addOneToIntByRef(ref intof3);
result = intresult == intof3;
Console.WriteLine($"result = {result}, intresult = {intresult}, intof3 = {intof3}");
//// Immutable types
//string startOfAlphabet = "abc";
//string alphabetresult = addEndOfAlphabet(startOfAlphabet);
//Console.WriteLine($"alphabetresult = {alphabetresult}, startofAlphabet = {startOfAlphabet}");
//// Also DateTime, TimeSpan, Uri, Tuple and others
//// Nulls and un-assigned values
////int a = null; // Not allowed
//MyNumber b = null; // This is ok, why? Note would try and avoid this in real life due to error below
////Console.WriteLine($"Value of b.Value = {b.Value}"); // This will cause runtime error;
//b = new MyNumber();
//Console.WriteLine($"Value of b.Value = {b.Value}");
//// For value types can use nullable wrappers
//int? c = null;
//Console.WriteLine($"Value of c = {c}");
////Console.WriteLine($"Value of c.Value = {c.Value}"); // Like example above this will cause runtime error
//// is equivalent to
//Nullable<int> d = null;
//// is equivalent to
//Nullable<int> e = new Nullable<int>();
//Console.WriteLine($"Value of d = {d}");
//Console.WriteLine($"Value of e = {e}");
////Console.WriteLine($"Value of d.Value = {d.Value}"); // Again will throw runtime error
////Console.WriteLine($"Value of e.Value = {e.Value}"); // Again will throw runtime error
}
private static int addOneToClassInstance(MyNumber number)
{
number.Value = number.Value + 1;
return(number.Value);
}
