Sorting Collection of Custom Type using Generic

Sponsored by

Become a Sponsor

Similar ArticlesMost ReadTop RatedLatest

Latest Jobs

dot net developer

MCA

.NET Developer Needed

.Net Developer

Senior .Net Software Engineer

Senior Software Engineer

Senior WPF Developer

Software Developer

Application Developer

More ...

Latest Interview Questions

What is lazy loading?

What is Replication in MS SQL. ? Type of Replication.?

What are Value types and Reference types ?

What is boxing and unboxing ?

What are different types that a variable can be defined and their scopes ?

What is Strong name ?

Different types of authentication modes in .NET Framework ?

What is an Assembly ?

What is the difference between Metadata and Menifest ?

What is delay signing?

More ...

Introduction:

This article describes the sorting techinque using Generic that can be implemented in any custom type collection based on the selected property.

For sorting any custom type the class must implement the System.IComparable interface which allow the object to be sorted based on some specified key.

Here is the definition:

Public Interface IComparable

Function CompareTo(ByVal o As Object) As Integer

End Interface

Now let us assume we have a Car class and if we want to sort the collection of car objects then we must implement IComparable interface and put the logic of how our car object is to be sorted in the CompareTo method

Public Class Car

Implements IComparable

Function IComparable.CompareTo(ByVal obj As Object) As Integer

Dim temp As Car = CType(obj, Car)

If Me.carID > temp.carID Then

Return 1

End If

If Me.carID < temp.carID Then

Return -1

Else

Return 0

End If

End Function

End Class

As you can see, the logic behind CompareTo() is to test the incoming type against the current instance based on a specific point of data. The return value of CompareTo() is used to discover if this type is less than, greater than, or equal to the object it is being compared with (see below).

CompareTo()	Return Value Meaning
Any number less than zero	This instance comes before the specified object in the sort order.
Zero	This instance is equal to the specified object.
Any number greater than zero	This instance comes after the specified object in the sort order.

Now if suppose we have more object in our application for example bus, two wheeler etc. then for each object we have to implement the IComparable interface in all the classes and implement the CompareTo() method.

The ideal solution is to take advantage of the Generic and developed a Generic Comparable class which can be used by any of the business object in our system.

Here is the code for doing it.

#Region "directives"

Imports Microsoft.VisualBasic

Imports System

Imports System.Collections.Generic

Imports System.Collections

Imports System.Text

Imports System.Reflection

#End Region

Namespace GenericSortComponent

''' <summary>

''' This class is used to compare any

''' type(property) of a class for sorting.

''' This class automatically fetches the

''' type of the property and compares.

''' </summary>

Public NotInheritable Class GenericComparer(Of T)

Implements IComparer(Of T)

Public Enum SortOrder

Ascending

Descending

End Enum

#Region "member variables"

Private sortColumn_Renamed As String

Private sortingOrder_Renamed As SortOrder

#End Region

#Region "constructor"

Public Sub New(ByVal sortColumn_Renamed As String, ByVal sortingOrder_Renamed As SortOrder)

Me.sortColumn_Renamed = sortColumn_Renamed

Me.sortingOrder_Renamed = sortingOrder_Renamed

End Sub

#End Region

#Region "public property"

''' <summary>

''' Column Name(public property of the class) to be sorted.

''' </summary>

Public ReadOnly Property SortColumn() As String

Get

Return sortColumn_Renamed

End Get

End Property

''' <summary>

''' Sorting order.

''' </summary>

Public ReadOnly Property SortingOrder() As SortOrder

Get

Return sortingOrder_Renamed

End Get

End Property

#End Region

#Region "public methods"

''' <summary>

''' Compare interface implementation

''' </summary>

''' <param name="x">First Object</param>

''' <param name="y">Second Object</param>

''' <returns>Result of comparison</returns>

Public Function Compare(ByVal x As T, ByVal y As T) As Integer Implements IComparer(Of T).Compare

Dim propertyInfo As PropertyInfo = GetType(T).GetProperty(sortColumn_Renamed)

Dim obj1 As IComparable = CType(propertyInfo.GetValue(x, Nothing), IComparable)

Dim obj2 As IComparable = CType(propertyInfo.GetValue(y, Nothing), IComparable)

If sortingOrder_Renamed = SortOrder.Ascending Then

Return (obj1.CompareTo(obj2))

Else

Return (obj2.CompareTo(obj1))

End If

End Function

#End Region

End Class

End Namespace

Now suppose we have a Car class with property CarID and CarName then the below code demonstrate the sorting using GenericComparer class describe above.

Shared Sub Main(ByVal args As String())

Dim cars As List(Of Car) = New List(Of Car)()

cars.Add(New Car(1, "Maruti 800"))

cars.Add(New Car(2, "Honda City"))
.....

.....

cars.Sort(New GenericComparer(Of Car)("CarName", GenericComparer(Of Car).SortOrder.Ascending))

.....

.....
'display here
End Sub

Here in the above main method the cars contains a collection of Car object.

Now we pass the instance of GenericComparer class in the cars.Sort() method with the Sort Field and Sort Order passed in the constructor of the GenericComparer.

NOTE: THIS ARTICLE IS CONVERTED FROM C# TO VB.NET USING A CONVERSION TOOL. ORIGINAL ARTICLE CAN BE FOUND ON C# CORNER (http://www.c-sharpcorner.com/).