C# Starter L04-Collections

Mohammad Shakermohammadshaker.com

C# Programming Course@ZGTRShaker

2011, 2012, 2013, 2014

C# StarterL04 – Collections

Collections

Collectionsusing System;using System.Collections.Generic;

namespace ConsoleApplicationCourseTest{

class MainClass{

public static void Main(String[] args){

List<int> myInts = new List<int>();

myInts.Add(1);myInts.Add(2);myInts.Add(3);

for (int i = 0; i < myInts.Count; i++){

Console.WriteLine("MyInts: {0}", myInts[i]);}

}}

}



class MainClass{






}}

}



class MainClass{






}}

}



class MainClass{






}}

}



class MainClass{






}}

}



class MainClass{






}}

}



class MainClass{






}}

}

MyInts: 1MyInts: 2MyInts: 3Press any key to continue...

Collections - Dictionaries

• Let’s have the following classnamespace ConsoleApplicationCourseTest{

public class Customer{

public Customer(int id, string name){

_id = id;_name = name;

}

private int _id;public int ID{

get { return _id; }set { _id = value; }

}

private string _name;public string Name{

get { return _name; }set { _name = value; }

}}

}

Collections

• And have the following mainnamespace ConsoleApplicationCourseTest{

class MainClass{


Dictionary<int, Customer> customers = new Dictionary<int, Customer>();

Customer cust1 = new Customer(1, "Cust 1");Customer cust2 = new Customer(2, "Cust 2");Customer cust3 = new Customer(3, "Cust 3");

customers.Add(cust1.ID, cust1);customers.Add(cust2.ID, cust2);customers.Add(cust3.ID, cust3);

foreach (KeyValuePair<int, Customer> custKeyVal in customers){

Console.WriteLine("Customer ID: {0}, Name: {1}",custKeyVal.Key,custKeyVal.Value.Name);

}}

}}

Collections


class MainClass{







}}

}}

Collections


class MainClass{







}}

}}

Collections


class MainClass{







}}

}}

Customer ID: 1, Name: Cust 1Customer ID: 2, Name: Cust 2Customer ID: 3, Name: Cust 3Press any key to continue...

Collectionsnamespace ConsoleApplicationCourseTest{

class MainClass{


Dictionary<int, string> customers = new Dictionary<int, string>();

for (int i = 0; i < 3; i++){

customers.Add(i,"Cust" + i);}

foreach (KeyValuePair<int, string> custKeyVal in customers){

Console.WriteLine("Customer ID: {0}, Name: {1}",custKeyVal.Key,custKeyVal.Value);

}

Console.WriteLine();customers[1] = "ZGTR";



}}

}}


class MainClass{



for (int i = 0; i < 3; i++){




}




}}

}}


class MainClass{



for (int i = 0; i < 3; i++){




}




}}

}}

Customer ID: 0, Name: Cust0Customer ID: 1, Name: Cust1Customer ID: 2, Name: Cust2

Customer ID: 0, Name: Cust0Customer ID: 1, Name: ZGTRCustomer ID: 2, Name: Cust2Press any key to continue...

Collections

• System.Collections.Generic

• System.Collections

Collections

• foreach danger

– NEVER EVER manipulate (insertion, deletion) a collection in a “foreach” statement

– Just iterate (and/or update if you want.)

– But Why?

Collections

private void button1_Click(object sender, EventArgs e){

System.Collections.ArrayList arrList = new ArrayList();arrList.Add(new Button());arrList.Add(new TextBox());arrList.Add(new ComboBox());arrList.Add(new ListBox());

foreach (var item in arrList){

arrList.Remove(item);}

}

Collections

private void Test(){System.Collections.ArrayList arrList = new ArrayList();arrList.Add(new Button());arrList.Add(new TextBox());arrList.Add(new ComboBox());arrList.Add(new ListBox());

foreach (var item in arrList){

arrList.Remove(item);}

}

Collections

Collections

private void Test(){{

System.Collections.ArrayList arrList = new ArrayList();arrList.Add(new Button());arrList.Add(new TextBox());arrList.Add(new ComboBox());arrList.Add(new ListBox());

arrList.Clear();}

Clearing all the collection!

Collections

Collections

Collections

Collections

Collections

Collections

Collections

Collections

Collections

Collections

Collections

Collections

Collections


List<int> list1 = new List<int> { 1, 2, 3, 4, 5 };foreach (var i in list1){

Console.Write(i + ", ");}Console.WriteLine();List<int> list2 = list1.ConvertAll(x => 2 * x);foreach (var i in list2){

Console.Write(i + ", ");}

}

Collections





}

Collections

1, 2, 3, 4, 5,2, 4, 6, 8, 10, Press any key to continue...





}

Collections

public static void Main(){

List<PointF> lpf = new List<PointF>();

lpf.Add(new PointF(27.8F, 32.62F));lpf.Add(new PointF(99.3F, 147.273F));lpf.Add(new PointF(7.5F, 1412.2F));

Console.WriteLine();foreach (PointF p in lpf){

Console.WriteLine(p);}

List<Point> lp = lpf.ConvertAll(new Converter<PointF, Point>(PointFToPoint));

Console.WriteLine();foreach (Point p in lp){


}

public static Point PointFToPoint(PointF pf){

return new Point(((int)pf.X), ((int)pf.Y));}

Collections









}



Collections









}



Collections









}



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}



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}



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}



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}



Collections









}



{X=27.8, Y=32.62}{X=99.3, Y=147.273}{X=7.5, Y=1412.2}

{X=27,Y=32}{X=99,Y=147}{X=7,Y=1412}

Collections

string[] names ={ "Hartono, Tommy", "Adams, Terry", "Andersen, Henriette Thaulow",

"Hedlund, Magnus", "Ito, Shu" };Random random = new Random(DateTime.Now.Millisecond);

string name = names.ElementAt(random.Next(0, names.Length));

Console.WriteLine("The name chosen at random is '{0}'.", name);

Collections





Collections





Collections





Collections





Collections





Collections





The name chosen at random is 'Ito, Shu'.

Collections

Collections

Collections

Collections

• Find, FindAll

public List<T> FindAll(Predicate<T> match

)

Collections

// Search predicate returns true if a string ends in "saurus".private static bool EndsWithSaurus(String s){

if ((s.Length > 5) &&(s.Substring(s.Length - 6).ToLower() == "saurus"))

{return true;

}else{

return false;}

}

Collectionspublic static void Main()

{List<string> dinosaurs = new List<string> {"Velociraptor", "Deinonychus", "Dilophosaurus"};

Console.WriteLine("TrueForAll(EndsWithSaurus): {0}", dinosaurs.TrueForAll(EndsWithSaurus));Console.WriteLine("\nFind(EndsWithSaurus): {0}", dinosaurs.Find(EndsWithSaurus));Console.WriteLine("\nFindLast(EndsWithSaurus): {0}", dinosaurs.FindLast(EndsWithSaurus));Console.WriteLine("\nFindAll(EndsWithSaurus):");

List<string> sublist = dinosaurs.FindAll(EndsWithSaurus);

foreach (string dinosaur in sublist) { Console.WriteLine(dinosaur); }

Console.WriteLine("\n{0} elements removed by RemoveAll(EndsWithSaurus).", dinosaurs.RemoveAll(EndsWithSaurus));

Console.WriteLine("\nList now contains:");foreach (string dinosaur in dinosaurs) { Console.WriteLine(dinosaur); }

Console.WriteLine("\nExists(EndsWithSaurus): {0}", dinosaurs.Exists(EndsWithSaurus));}

Collections

// Search predicate returns true if a string ends in "saurus".private static bool EndsWithSaurus(String s){

if ((s.Length > 5) &&(s.Substring(s.Length - 6).ToLower() == "saurus"))

{return true;

}else{

return false;}

}

Collections

TrueForAll(EndsWithSaurus): False

Find(EndsWithSaurus): Dilophosaurus

FindLast(EndsWithSaurus): Dilophosaurus

FindAll(EndsWithSaurus):Dilophosaurus

1 elements removed by RemoveAll(EndsWithSaurus).

List now contains:VelociraptorDeinonychus

Exists(EndsWithSaurus): FalsePress any key to continue...

Collections

1: public sealed class Employee2: {3: public long Id { get; set; }4: public string Name { get; set; }5: public double Salary { get; set; }6: }

1: // empty2: var noEmployeeList = new List<Employee>();3: 4: // many items5: var employees = new List<Employee>6: {7: new Employee { Id = 1, Name = "Jim Smith", Salary = 12345.50 },8: new Employee { Id = 7, Name = "Jane Doe", Salary = 31234.50 },9: new Employee { Id = 9, Name = "John Doe", Salary = 13923.99 },10: new Employee { Id = 13, Name = "Jim Smith", Salary = 30123.49 }, 11: //... etc...12: };

Collections

1: public sealed class Employee2: {3: public long Id { get; set; }4: public string Name { get; set; }5: public double Salary { get; set; }6: }

1: // empty2: var noEmployeeList = new List<Employee>();3: 4: // many items5: var employees = new List<Employee>6: {7: new Employee { Id = 1, Name = "Jim Smith", Salary = 12345.50 },8: new Employee { Id = 7, Name = "Jane Doe", Salary = 31234.50 },9: new Employee { Id = 9, Name = "John Doe", Salary = 13923.99 },10: new Employee { Id = 13, Name = "Jim Smith", Salary = 30123.49 }, 11: //... etc...12: };

A sealed class cannot be inherited. It is an error to use a sealed class as a base class. Use the sealed modifier in a class declaration to prevent inheritance of the class. It is not permitted to use the abstract modifier with a sealed class. Structs are

implicitly sealed; therefore, they cannot be inherited

Collections

• Like First(), the Last() method will throw if there are no items (or no matches in the

case of predicates) in the enumerable:

• The LastOrDefault() methods will return a default(TSource) if the list is empty or

no matches are found:

1: // throws at runtime because empty enumerable.2: var empty = noEmployeeList.Last();3: 4: // this line will throw at runtime because there is no item that matches5: // even though the enumerable itself is not empty6: var noMatch = employees.Last(e => e.Id == 20);

1: // returns default(Employee) -- null -- because list is empty2: var empty = noEmployeeList.LastOrDefault();3: 4: // returns default(Employee) -- null -- because no item matches predicate.5: var noMatch = employees.Last(e => e.Id == 20);

Collections

• ElementAt()

1: 2: // returns the second employee (index == 1) which is Jane Doe, Id == 73: var janeDoe = employees.ElementAt(1);4: 5: // since there's not 30 employees, this one will throw exception6: var willThrow = employees.ElementAt(30);7: 8: // returns null because there aren't 30 employees, but we used the OrDefault flavor.9: var noMatch = employees.ElementAtOrDefault(30);

Collections

• Stack

public class SamplesStack{


// Creates and initializes a new Stack.Stack myStack = new Stack();myStack.Push("Hello");myStack.Push("World");myStack.Push("!");

// Displays the properties and values of the Stack.Console.WriteLine("myStack");Console.WriteLine("\tCount: {0}", myStack.Count);Console.Write("\tValues:");PrintValues(myStack);

}public static void PrintValues(IEnumerable myCollection){

foreach (Object obj in myCollection)Console.Write(" {0}", obj);

Console.WriteLine();}

}

Collections

• Stack

public class SamplesStack{


// Creates and initializes a new Stack.Stack myStack = new Stack();myStack.Push("Hello");myStack.Push("World");myStack.Push("!");

// Displays the properties and values of the Stack.Console.WriteLine("myStack");Console.WriteLine("\tCount: {0}", myStack.Count);Console.Write("\tValues:");PrintValues(myStack);

}public static void PrintValues(IEnumerable myCollection){

foreach (Object obj in myCollection)Console.Write(" {0}", obj);

Console.WriteLine();}

}

myStackCount: 3Values: ! World Hello

Press any key to continue...

Play more with Collections

More Collections Functionalities

• Let’s have the following class

public class PointClass{

public float XLocation { set; get; }public float YLocation { set; get; }

public PointClass(float xLocation, float yLocation){

this.XLocation = xLocation;this.YLocation = yLocation;

}

public override string ToString(){

return String.Format("X = {0}, Y = {1}", this.XLocation, this.YLocation);}

}

More Collections Functionalitiespublic class IsTest{

public static void PrintToConsole(List<PointClass> list, string Msg){

Console.WriteLine(Msg);foreach (var point in list){

Console.WriteLine(point.ToString());}

}public static void Main(){

List<PointClass> listOfPoints = new List<PointClass>(){

new PointClass(1, 0),new PointClass(1, 0),new PointClass(2, 0),new PointClass(0, 0)

};PrintToConsole(listOfPoints, "Before Sorting");listOfPoints.Sort();PrintToConsole(listOfPoints, "After default sorting");

}}

More Collections Functionalitiespublic class IsTest{







};PrintToConsole(listOfPoints, "Before Sorting");listOfPoints.Sort();PrintToConsole(listOfPoints, "After default sorting");

}}






}public static int SortByXLocation(PointClass point1, PointClass point2){

if (point1.XLocation > point2.XLocation)return +1;

else if (point1.XLocation < point2.XLocation)return -1;

elsereturn 0;




};PrintToConsole(listOfPoints, "Before sorting");listOfPoints.Sort(SortByXLocation);PrintToConsole(listOfPoints, "After our cool sorting!");

}








elsereturn 0;





}








elsereturn 0;





}

Before sortingX = 1, Y = 0X = 1, Y = 0X = 2, Y = 0X = 0, Y = 0After our cool sorting!X = 0, Y = 0X = 1, Y = 0X = 1, Y = 0X = 2, Y = 0Press any key to continue...








elsereturn 0;





}

Before sortingX = 1, Y = 0X = 1, Y = 0X = 2, Y = 0X = 0, Y = 0After our cool sorting!X = 0, Y = 0X = 1, Y = 0X = 1, Y = 0X = 2, Y = 0Press any key to continue...






}




};Console.WriteLine(listOfPoints.Contains(new PointClass(1, 0)));

}





}





}

FalsePress any key to continue...





}





}


Why?!





}





}


Because it’s comparing

References not Values





}





}


So, what to do to

compare values?!


More Collections Functionalitiespublic class PointClass : IEquatable<PointClass>{




}



public bool Equals(PointClass other){

if ((this.XLocation == other.XLocation) && (this.YLocation == other.YLocation)){

return true;}else{

return false;}

}}





}





return true;}else{

return false;}

}}





}





return true;}else{

return false;}

}}






}





return true;}else{

return false;}

}}






}






}

TruePress any key to continue...






}

TruePress any key to continue...

“Cross” Collections

“CROSS” Collections

public class PointClass{




}



}



List<PointClass> listOfHalls = new List<PointClass>(){

new PointClass(1, 0),new PointClass(1, 0),new PointClass(2, 3),

};List<PointClass> listOfLabs = new List<PointClass>()

{new PointClass(1, 7),new PointClass(10, 2),

};Dictionary<string, List<PointClass>> dic = new Dictionary<string, List<PointClass>>();dic.Add("HallsLocations", listOfHalls);dic.Add("LabsLocations", listOfLabs);

}








}








}









};Dictionary<string, List<PointClass>> dic = new Dictionary<string, List<PointClass>>();dic.Add("HallsLocations", listOfHalls);dic.Add("LabsLocations", listOfLabs);foreach (PointClass point in dic["LabsLocations"]){

Console.WriteLine(point);}

}







};Dictionary<string, List<PointClass>> dic = new Dictionary<string, List<PointClass>>();dic.Add("HallsLocations", listOfHalls);dic.Add("LabsLocations", listOfLabs);foreach (PointClass point in dic["LabsLocations"]){


}

X = 1, Y = 7X = 10, Y = 2Press any key to continue...







};Dictionary<string, List<PointClass>> dic = new Dictionary<string, List<PointClass>>();dic.Add("HallsLocations", listOfHalls);dic.Add("LabsLocations", listOfLabs);dic["LabsLocations"].ForEach(PrintMe);

}

private static void PrintMe(PointClass point){








};Dictionary<string, List<PointClass>> dic = new Dictionary<string, List<PointClass>>();dic.Add("HallsLocations", listOfHalls);dic.Add("LabsLocations", listOfLabs);dic["LabsLocations"].ForEach(PrintMe);

}

private static void PrintMe(PointClass point){


X = 1, Y = 7X = 10, Y = 2Press any key to continue...








};Dictionary<string, List<PointClass>> dic = new Dictionary<string, List<PointClass>>();dic.Add("HallsLocations", listOfHalls);dic.Add("LabsLocations", listOfLabs);dic["LabsLocations"].Add(new PointClass(8,8));

}








};Dictionary<string, List<PointClass>> dic = new Dictionary<string, List<PointClass>>();dic.Add("HallsLocations", listOfHalls);dic.Add("LabsLocations", listOfLabs);dic["LabsLocations"].Add(new PointClass(8,8));Console.WriteLine(dic["LabsLocations"][2]);

}








}








}

X = 8, Y = 8Press any key to continue...







};Dictionary<string, List<PointClass>> dic = new Dictionary<string, List<PointClass>>();dic.Add("HallsLocations", listOfHalls);dic.Add("LabsLocations", listOfLabs);dic["LabsLocations"].Add(new PointClass(8,8));Console.WriteLine(dic["LabsLocations"].Last());

}







};Dictionary<string, List<PointClass>> dic = new Dictionary<string, List<PointClass>>();dic.Add("HallsLocations", listOfHalls);dic.Add("LabsLocations", listOfLabs);dic["LabsLocations"].Add(new PointClass(8,8));Console.WriteLine(dic["LabsLocations"].Last());

}

X = 8, Y = 8Press any key to continue...

Technology

C# Starter L04-Collections