To Explain the Generics in VB.NET I am going to create a class called List which you can add integer to the list
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 |
Public Class List Private items() As Integer Private index As Integer Public Sub New(ByVal size As Integer) ReDim items(size - 1) index = 0 End Sub Public Sub Add(ByVal number As Integer) items(index) = number index += 1 End Sub End Class |
Inside the Sub Main() I will add two integers
|
1 2 3 4 5 6 7 8 9 |
Module Module1 Sub Main() Dim myList As New List(2) myList.Add(1) myList.Add(2) End Sub End Module |
How do you change the class to add String values
You create a new class then copy the code and change Integer to String
Like the code below
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 |
Public Class StringList Private items() As String Private index As Integer Public Sub New(ByVal size As Integer) ReDim items(size - 1) index = 0 End Sub Public Sub Add(ByVal str As String) items(index) = str index += 1 End Sub End Class |
Although you have used the code reusability this is not good approach. SO VB.NET has Generics for this
I am using new keyword Of with type
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 |
Public Class List(Of type) Private items() As type Private index As Integer Public Sub New(ByVal size As Integer) ReDim items(size - 1) index = 0 End Sub Public Sub Add(ByVal item As type) items(index) = item index += 1 End Sub End Class |
When you create the instance form this class you have to use Of Integer as shown below
|
1 2 3 4 5 |
Sub Main() Dim myList As New List(Of Integer)(2) myList.Add(1) myList.Add(2) End Sub |
Now you can used this generic class for any data type which you find in the VB.NET