Ariel Erlijman

Build Typesafe Generic Classes

Example 1

Public Class GenericList(Of ItemType)
 'Some Code
End Class

Example 2

Public Class GenericList(Of Item Type)
Inherits CollectionBase

Public Function Add(ByVal value as ItemType) as Integer
 Return List.Add(value)
End Function

Public Sub Remove(ByVal value as ItemValue)
 List.Remove(value)
End Sub

Public ReadOnly Property Item(ByVal index as Integer) as ItemType
 Get
  Return CType(List.Item(index),ItemType)
 End Get
End Property

End Class

Program Code

Dim List as New GenericList(Of String)
List.Add("blue")
List.Add("red")

List.Add(Guid.NewGuid()) ' Will be detected by the compiler

Example 3 - More than one type parameter in the class

Public Class GenerichashTable(Of ItemType, KeyType)
 Inherits DictionaryBase
 'Code
End Class
 

Example 4 - Define Constraints to Parameters

Public Class SerializableList(Of ItemType as ISerializable)
 Inherits CollectionBase
 'Code
End Class

Public Class ControlCollection(Of ItemType as Control)
 Inherits CollectionBase
 'Code
End Class

If you want your class to create an instance of the Item

Public Class GenericList(Of ItemType as New)
 Inherits CollectionBase
 'Code
End Class

Example 5 - Define more than one constraint

Public Class GenericList(Of  ItemType as {ISerializable, New})
 Inherits CollectionBase
 'Code
End Class

Generics also works with structures, interfaces, deletates and methods.

This entry was posted on Wednesday, December 13th, 2006 at 8:13 am and is filed under VB.NET Useful Code. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.