XML Feeds
In Java, they have had a set implementation for ages. Well, .Net has it too. So no more need to import Iesi.set. The HashSet<T> or HashSet(Of T) is one of the collections you need most. For this to work, your objects need to override the Equals and GetHashCode functions, so that they reflect the business rules.
I have an example here of a List:
- Module Module1
- Sub Main()
- Dim personlist As List(Of Person) = New List(Of Person)()
- Dim person1 As Person = New Person("Chris", "Baes")
- Dim person2 As Person = New Person("Chris", "Baes")
- Console.WriteLine(person1.Equals(person2))
- Dim person3 As Person = New Person("Chris1", "Baes")
- Console.WriteLine(person3.Equals(person2))
- personlist.Add(person1)
- Console.WriteLine(personlist.Count)
- personlist.Add(person2)
- Console.WriteLine(personlist.Count)
- personlist.Add(person3)
- Console.WriteLine(personlist.Count)
- Console.ReadLine()
- End Sub
- Public Class Person
- Implements IComparable
- Private _firstName As String
- Private _lastName As String
- Public Sub New(ByVal FirstName As String, ByVal LastName As String)
- _firstName = FirstName
- _lastName = LastName
- End Sub
- Public Property FirstName() As String
- Get
- Return _firstName
- End Get
- Set(ByVal value As String)
- _firstName = value
- End Set
- End Property
- Public Property LastName() As String
- Get
- Return _lastName
- End Get
- Set(ByVal value As String)
- _lastName = value
- End Set
- End Property
- Public Overrides Function Equals(ByVal obj As Object) As Boolean
- Return obj.FirstName.Equals(Me.FirstName)
- End Function
- Public Overrides Function GetHashCode() As Integer
- Return Me.FirstName.GetHashCode()
- End Function
- Public Function CompareTo(ByVal obj As Object) As Integer Implements System.IComparable.CompareTo
- obj.FirstName.compareto(Me.FirstName)
- End Function
- End Class
- End Module
And the C# implementation:
- using System;
- using System.Collections.Generic;
- using System.Linq;
- using System.Text;
- namespace Testing_list_C
- {
- class Program
- {
- static void Main(string[] args)
- {
- List<Person> personlist = new List<Person>();
- Person person1 = new Person("Chris", "Baes");
- Person person2 = new Person("Chris", "Baes");
- Console.WriteLine(person1.Equals(person2));
- Person person3 = new Person("Chris1", "Baes");
- Console.WriteLine(person3.Equals(person2));
- personlist.Add(person1);
- Console.WriteLine(personlist.Count);
- personlist.Add(person2);
- Console.WriteLine(personlist.Count);
- personlist.Add(person3);
- Console.WriteLine(personlist.Count);
- Console.ReadLine();
- }
- }
- class Person:IEquatable<Person>
- {
- String firstName;
- String lastName;
- public Person(String FirstName, String LastName)
- {
- firstName = FirstName;
- lastName = LastName;
- }
- public String FirstName
- {
- get
- {
- return firstName;
- }
- set
- {
- firstName = value;
- }
- }
- public String LastName
- {
- get
- {
- return lastName;
- }
- set
- {
- lastName = value;
- }
- }
- public bool Equals(Person obj)
- {
- return obj.firstName.Equals(this.firstName);
- }
- public bool Equals(Object obj)
- {
- return ((Person)obj).firstName.Equals(this.firstName);
- }
- }
- }
The Result will be:
True
False
1
2
3
If you replace the List with HashSet then the result will be:
True
False
1
1
2
The only problem is that you will not get any sort of exceptions. It will just not add it to the HashSet and go on with its business as usual. So I wouldn’t call this very user friendly because the user doesn’t understand, you have to explain, but I guess that is our job and it is easily solved with contains.
Christiaan is a forensic technician who programs on the side, although my function description says that I do IT-things for 90% of the time . I'm an avid VB.NET fan and I use lots of the ALT.Net techniques, like unit-testing, nhibernate, logging, IoC, ...
LTD Social Sitings
Note: Watch for social icons on posts by your favorite authors to follow their postings on these and other social sites.