C#

out : Updating a Value type from called function

public static void ValueTypes()
{
    var x = 2;
    Console.WriteLine("ValueTypes: var x=2");
    Console.WriteLine("ValueTypes: Five(x): Before: {0}", x);
    // passes the VALUE to func so WILL NOT CHANGE ITS VALUE
    Console.WriteLine("ValueTypes: Five(x):calling..");
    Five(x);
    Console.WriteLine("ValueTypes: Five(x): AFTER: {0}", x);
}

static void Five(int a)
{
    a = 5;
    Console.WriteLine("ValueTypes: IN..Fix(int a): assigning a=5");
}

Value type

int is value type

int x = 1;
int x;
int x = 0;
int x = null // throws compile error

Reference type

var employee = new employee();

Memory Considerations

using new, consumes memory

once variable is no longer used, the memory is still consumed, but no accessible

Memory Leaks occur when this happens

Garbage Collector will cleanup periodically, but this also consumes CPU power to manage

So writing lean code is important for larger or load-intensive applications

Stack

Memory management here is simpler

int x;

Heap ( with Garbage Collector )

More complex memory management

new Employee()

Given Original Code

Employee Class Field

public int Business; //index of the business name

Assignment

                    var emp = new Employee();

                    emp.Business = Util.EmployeeTrackerUtils.AskInt("Business Index Number: " +
                        "\n0:Apple \n1:Microsoft \n2:Samsung");
                    emp.Birthday = Util.EmployeeTrackerUtils.Ask("Employee Birthday: ");

Foreach

BreakPoint

Step Over

Step Into

Continue

RunToHere

Exception catching must go from specific to generic

try{code}
catch{Specific}
catch{Generic}

Catching an Exception & Throwing a Message to Calling Method

Called method can catch an exception and 'throw new' message

        public static double AskDouble(string question)
        {
            try
            {
                System.Console.WriteLine(question);
                return double.Parse(Console.ReadLine());
            }
            catch(Exception)
            {
                // throws the error message up to calling methods
                throw new FormatException("Input was not a number");
            }
        }

Calling Try/Catch Block can receive the THROWN message

                catch (FormatException msg)
                {
                    Console.WriteLine(msg);
                }

Console

int.Parse()

string.Parse()

double.Parse()

TryParse()

// Udpated for error handling on int.Parse
emp.Score = int.Parse(Util.EmployeeTrackerUtils.Ask("Employee Score: "));
int.TryParse(Util.EmployeeTrackerUtils.Ask("Employee Score: "), out emp.Score);

using System.Collections.Generic;

Lists

List<string> sList = new List<string>();

For

ForEach

While

DoWhile

Continue

Break

if-then-else

Switch

AND OR

Operators

Prefix / PostFix

Ternary Operator

Operator Precedence

IS Evaluation

AS Evaluation

Console.WriteLine()

//Console.WriteLine()
Console.WriteLine("Hello World!");
Console.WriteLine("{0}","Hello World!");
Console.WriteLine("{0} {1}", "Hello", "World!");

Ouput

Hello World!
Hello World!
Hello World!

Console.ReadLine()

        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
            string input = Console.ReadLine();
            Console.WriteLine("Input value = {0}", input);
        }

Output

Hello World!
MyInput
Input value = MyInput
Press any key to continue . . .