The document discusses collections in C# programming. It shows examples of using List and Dictionary collections to store and retrieve data. A List is used to store integer values and later iterate through them. A Dictionary is used to store Customer objects mapped by ID. The document also demonstrates converting between collection types using ConvertAll and a custom converter.

1. Mohammad Shaker
mohammadshaker.com
C# Programming Course
@ZGTRShaker
2011, 2012, 2013, 2014
C# Starter
L04 – Collections

2. Collections

3. Collections
using 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]);
}
}
}
}

4. Collections
using 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]);
}
}
}
}

5. Collections
using 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]);
}
}
}
}

6. Collections
using 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]);
}
}
}
}

7. Collections
using 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]);
}
}
}
}

8. Collections
using 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]);
}
}
}
}

9. Collections
using 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]);
}
}
}
}
MyInts: 1
MyInts: 2
MyInts: 3
Press any key to continue...

10. Collections - Dictionaries
• Let’s have the following class
namespace 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; }
}
}
}

11. Collections
• And have the following main
namespace ConsoleApplicationCourseTest
{
class MainClass
{
public static void Main(String[] args)
{
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);
}
}
}
}

12. Collections
namespace ConsoleApplicationCourseTest
{
class MainClass
{
public static void Main(String[] args)
{
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);
}
}
}
}

13. Collections
namespace ConsoleApplicationCourseTest
{
class MainClass
{
public static void Main(String[] args)
{
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);
}
}
}
}

14. Collections
namespace ConsoleApplicationCourseTest
{
class MainClass
{
public static void Main(String[] args)
{
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);
}
}
}
}
Customer ID: 1, Name: Cust 1
Customer ID: 2, Name: Cust 2
Customer ID: 3, Name: Cust 3
Press any key to continue...

15. Collections
namespace ConsoleApplicationCourseTest
{
class MainClass
{
public static void Main(String[] args)
{
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";
foreach (KeyValuePair<int, string> custKeyVal in customers)
{
Console.WriteLine("Customer ID: {0}, Name: {1}",
custKeyVal.Key,
custKeyVal.Value);
}
}
}
}

16. Collections
namespace ConsoleApplicationCourseTest
{
class MainClass
{
public static void Main(String[] args)
{
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";
foreach (KeyValuePair<int, string> custKeyVal in customers)
{
Console.WriteLine("Customer ID: {0}, Name: {1}",
custKeyVal.Key,
custKeyVal.Value);
}
}
}
}

17. Collections
namespace ConsoleApplicationCourseTest
{
class MainClass
{
public static void Main(String[] args)
{
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";
foreach (KeyValuePair<int, string> custKeyVal in customers)
{
Console.WriteLine("Customer ID: {0}, Name: {1}",
custKeyVal.Key,
custKeyVal.Value);
}
}
}
}
Customer ID: 0, Name: Cust0
Customer ID: 1, Name: Cust1
Customer ID: 2, Name: Cust2
Customer ID: 0, Name: Cust0
Customer ID: 1, Name: ZGTR
Customer ID: 2, Name: Cust2
Press any key to continue...

18. Collections
• System.Collections.Generic
• System.Collections

19. Collections
• foreach danger
– NEVER EVER manipulate (insertion, deletion) a collection in a “foreach” statement
– Just iterate (and/or update if you want.)
– But Why?

20. 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);
}
}

21. 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);
}
}

22. Collections

23. 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!

24. Collections

25. Collections

26. Collections

33. Collections

34. Collections

35. Collections

36. Collections

37. Collections

38. Collections

39. Collections

40. Collections

41. Collections

42. Collections
public static void Main(String[] args)
{
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 + ", ");
}
}

43. Collections
public static void Main(String[] args)
{
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 + ", ");
}
}

44. Collections
1, 2, 3, 4, 5,
2, 4, 6, 8, 10, Press any key to continue...
public static void Main(String[] args)
{
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 + ", ");
}
}

45. 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)
{
Console.WriteLine(p);
}
}
public static Point PointFToPoint(PointF pf)
{
return new Point(((int)pf.X), ((int)pf.Y));
}

46. 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)
{
Console.WriteLine(p);
}
}
public static Point PointFToPoint(PointF pf)
{
return new Point(((int)pf.X), ((int)pf.Y));
}

47. 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)
{
Console.WriteLine(p);
}
}
public static Point PointFToPoint(PointF pf)
{
return new Point(((int)pf.X), ((int)pf.Y));
}

48. 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)
{
Console.WriteLine(p);
}
}
public static Point PointFToPoint(PointF pf)
{
return new Point(((int)pf.X), ((int)pf.Y));
}

49. 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)
{
Console.WriteLine(p);
}
}
public static Point PointFToPoint(PointF pf)
{
return new Point(((int)pf.X), ((int)pf.Y));
}

50. 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)
{
Console.WriteLine(p);
}
}
public static Point PointFToPoint(PointF pf)
{
return new Point(((int)pf.X), ((int)pf.Y));
}

51. 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)
{
Console.WriteLine(p);
}
}
public static Point PointFToPoint(PointF pf)
{
return new Point(((int)pf.X), ((int)pf.Y));
}

52. 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)
{
Console.WriteLine(p);
}
}
public static Point PointFToPoint(PointF pf)
{
return new Point(((int)pf.X), ((int)pf.Y));
}

53. 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)
{
Console.WriteLine(p);
}
}
public static Point PointFToPoint(PointF pf)
{
return new Point(((int)pf.X), ((int)pf.Y));
}
{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}

55. 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);

56. 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);

57. 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);

58. 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);

59. 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);

60. 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);

61. 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);
The name chosen at random is 'Ito, Shu'.

62. Collections

63. Collections

64. Collections

65. Collections
• Find, FindAll
public List<T> FindAll(
Predicate<T> match
)

66. 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;
}
}

67. Collections
public 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));
}

68. 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;
}
}

69. Collections
TrueForAll(EndsWithSaurus): False
Find(EndsWithSaurus): Dilophosaurus
FindLast(EndsWithSaurus): Dilophosaurus
FindAll(EndsWithSaurus):
Dilophosaurus
1 elements removed by RemoveAll(EndsWithSaurus).
List now contains:
Velociraptor
Deinonychus
Exists(EndsWithSaurus): False
Press any key to continue...

70. Collections
1: public sealed class Employee
2: {
3: public long Id { get; set; }
4: public string Name { get; set; }
5: public double Salary { get; set; }
6: }
1: // empty
2: var noEmployeeList = new List<Employee>();
3:
4: // many items
5: 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: };

71. Collections
1: public sealed class Employee
2: {
3: public long Id { get; set; }
4: public string Name { get; set; }
5: public double Salary { get; set; }
6: }
1: // empty
2: var noEmployeeList = new List<Employee>();
3:
4: // many items
5: 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

72. 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 matches
5: // even though the enumerable itself is not empty
6: var noMatch = employees.Last(e => e.Id == 20);
1: // returns default(Employee) -- null -- because list is empty
2: var empty = noEmployeeList.LastOrDefault();
3:
4: // returns default(Employee) -- null -- because no item matches predicate.
5: var noMatch = employees.Last(e => e.Id == 20);

73. Collections
• ElementAt()
1:
2: // returns the second employee (index == 1) which is Jane Doe, Id == 7
3: var janeDoe = employees.ElementAt(1);
4:
5: // since there's not 30 employees, this one will throw exception
6: 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);

74. Collections
• Stack
public class SamplesStack
{
public static void Main()
{
// 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();
}
}

75. Collections
• Stack
public class SamplesStack
{
public static void Main()
{
// 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();
}
}
myStack
Count: 3
Values: ! World Hello
Press any key to continue...

76. Play more with Collections

77. 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);
}
}

78. More Collections Functionalities
public 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");
}
}

80. More Collections Functionalities
public 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");
}
}

82. More Collections Functionalities

83. More Collections Functionalities
public static void PrintToConsole(List<PointClass> list, string Msg)
{
Console.WriteLine(Msg);
foreach (var point in list)
{
Console.WriteLine(point.ToString());
}
}
public static int SortByXLocation(PointClass point1, PointClass point2)
{
if (point1.XLocation > point2.XLocation)
return +1;
else if (point1.XLocation < point2.XLocation)
return -1;
else
return 0;
}
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(SortByXLocation);
PrintToConsole(listOfPoints, "After our cool sorting!");
}

84. More Collections Functionalities
public static void PrintToConsole(List<PointClass> list, string Msg)
{
Console.WriteLine(Msg);
foreach (var point in list)
{
Console.WriteLine(point.ToString());
}
}
public static int SortByXLocation(PointClass point1, PointClass point2)
{
if (point1.XLocation > point2.XLocation)
return +1;
else if (point1.XLocation < point2.XLocation)
return -1;
else
return 0;
}
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(SortByXLocation);
PrintToConsole(listOfPoints, "After our cool sorting!");
}

85. More Collections Functionalities
public static void PrintToConsole(List<PointClass> list, string Msg)
{
Console.WriteLine(Msg);
foreach (var point in list)
{
Console.WriteLine(point.ToString());
}
}
public static int SortByXLocation(PointClass point1, PointClass point2)
{
if (point1.XLocation > point2.XLocation)
return +1;
else if (point1.XLocation < point2.XLocation)
return -1;
else
return 0;
}
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(SortByXLocation);
PrintToConsole(listOfPoints, "After our cool sorting!");
}
Before sorting
X = 1, Y = 0
X = 1, Y = 0
X = 2, Y = 0
X = 0, Y = 0
After our cool sorting!
X = 0, Y = 0
X = 1, Y = 0
X = 1, Y = 0
X = 2, Y = 0
Press any key to continue...

86. More Collections Functionalities
public static void PrintToConsole(List<PointClass> list, string Msg)
{
Console.WriteLine(Msg);
foreach (var point in list)
{
Console.WriteLine(point.ToString());
}
}
public static int SortByXLocation(PointClass point1, PointClass point2)
{
if (point1.XLocation > point2.XLocation)
return +1;
else if (point1.XLocation < point2.XLocation)
return -1;
else
return 0;
}
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(SortByXLocation);
PrintToConsole(listOfPoints, "After our cool sorting!");
}
Before sorting
X = 1, Y = 0
X = 1, Y = 0
X = 2, Y = 0
X = 0, Y = 0
After our cool sorting!
X = 0, Y = 0
X = 1, Y = 0
X = 1, Y = 0
X = 2, Y = 0
Press any key to continue...

87. More Collections Functionalities

90. More Collections Functionalities
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)
};
Console.WriteLine(listOfPoints.Contains(new PointClass(1, 0)));
}

91. More Collections Functionalities
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)
};
Console.WriteLine(listOfPoints.Contains(new PointClass(1, 0)));
}
False
Press any key to continue...

92. More Collections Functionalities
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)
};
Console.WriteLine(listOfPoints.Contains(new PointClass(1, 0)));
}
False
Press any key to continue...
Why?!

93. More Collections Functionalities
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)
};
Console.WriteLine(listOfPoints.Contains(new PointClass(1, 0)));
}
False
Press any key to continue...
Because it’s comparing
References not Values

94. More Collections Functionalities
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)
};
Console.WriteLine(listOfPoints.Contains(new PointClass(1, 0)));
}
False
Press any key to continue...
So, what to do to
compare values?!

95. More Collections Functionalities

96. More Collections Functionalities
public class PointClass : IEquatable<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);
}
public bool Equals(PointClass other)
{
if ((this.XLocation == other.XLocation) && (this.YLocation == other.YLocation))
{
return true;
}
else
{
return false;
}
}
}

97. More Collections Functionalities
public class PointClass : IEquatable<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);
}
public bool Equals(PointClass other)
{
if ((this.XLocation == other.XLocation) && (this.YLocation == other.YLocation))
{
return true;
}
else
{
return false;
}
}
}

98. More Collections Functionalities
public class PointClass : IEquatable<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);
}
public bool Equals(PointClass other)
{
if ((this.XLocation == other.XLocation) && (this.YLocation == other.YLocation))
{
return true;
}
else
{
return false;
}
}
}

99. More Collections Functionalities

100. More Collections Functionalities
public class PointClass : IEquatable<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);
}
public bool Equals(PointClass other)
{
if ((this.XLocation == other.XLocation) && (this.YLocation == other.YLocation))
{
return true;
}
else
{
return false;
}
}
}

101. More Collections Functionalities
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)
};
Console.WriteLine(listOfPoints.Contains(new PointClass(0, 0)));
}

102. More Collections Functionalities
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)
};
Console.WriteLine(listOfPoints.Contains(new PointClass(0, 0)));
}
True
Press any key to continue...

103. More Collections Functionalities
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)
};
Console.WriteLine(listOfPoints.Contains(new PointClass(0, 0)));
}
True
Press any key to continue...

104. “Cross” Collections

105. “CROSS” Collections
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);
}
}

106. “CROSS” Collections
public static void Main()
{
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);
}

107. “CROSS” Collections
public static void Main()
{
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);
}

108. “CROSS” Collections
public static void Main()
{
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);
}

109. “CROSS” Collections

110. “CROSS” Collections

111. “CROSS” Collections
public static void Main()
{
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);
foreach (PointClass point in dic["LabsLocations"])
{
Console.WriteLine(point);
}
}

112. “CROSS” Collections
public static void Main()
{
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);
foreach (PointClass point in dic["LabsLocations"])
{
Console.WriteLine(point);
}
}
X = 1, Y = 7
X = 10, Y = 2
Press any key to continue...

113. “CROSS” Collections
public static void Main()
{
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);
dic["LabsLocations"].ForEach(PrintMe);
}
private static void PrintMe(PointClass point)
{
Console.WriteLine(point);
}

114. “CROSS” Collections
public static void Main()
{
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);
dic["LabsLocations"].ForEach(PrintMe);
}
private static void PrintMe(PointClass point)
{
Console.WriteLine(point);
}
X = 1, Y = 7
X = 10, Y = 2
Press any key to continue...

115. “CROSS” Collections

116. “CROSS” Collections
public static void Main()
{
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);
dic["LabsLocations"].Add(new PointClass(8,8));
}

117. “CROSS” Collections

118. “CROSS” Collections
public static void Main()
{
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);
dic["LabsLocations"].Add(new PointClass(8,8));
Console.WriteLine(dic["LabsLocations"][2]);
}

119. “CROSS” Collections
public static void Main()
{
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);
dic["LabsLocations"].Add(new PointClass(8,8));
Console.WriteLine(dic["LabsLocations"][2]);
}

120. “CROSS” Collections
public static void Main()
{
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);
dic["LabsLocations"].Add(new PointClass(8,8));
Console.WriteLine(dic["LabsLocations"][2]);
}
X = 8, Y = 8
Press any key to continue...

121. “CROSS” Collections
public static void Main()
{
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);
dic["LabsLocations"].Add(new PointClass(8,8));
Console.WriteLine(dic["LabsLocations"].Last());
}

122. “CROSS” Collections
public static void Main()
{
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);
dic["LabsLocations"].Add(new PointClass(8,8));
Console.WriteLine(dic["LabsLocations"].Last());
}
X = 8, Y = 8
Press any key to continue...