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  • Status: Solved
  • Priority: Medium
  • Security: Public
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Adding an event to list(Of T)

Is there a means to add an event to generic.list(Of T)?
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Alyanto
Asked:
Alyanto
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1 Solution
 
Wayne Taylor (webtubbs)Commented:
Yes, but you will have to create your own custom class to handle the events...

For example, this code will show a message box with the newly added item when the button is clicked.
Public Class Form1

    Private WithEvents myList As MyCustomList

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

        myList = New MyCustomList

    End Sub

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        myList.Add("new item")
    End Sub

    Private Sub myList_ItemAdded(ByRef sender As System.Collections.Generic.List(Of String), ByRef item As String) Handles myList.ItemAdded
        MessageBox.Show("New item added: " & item)
    End Sub

End Class

Public Class MyCustomList
    Inherits Generic.List(Of String)

    Public Sub New()
        MyBase.New()
    End Sub

    Public Event ItemAdded(ByRef sender As List(Of String), ByRef item As String)

    Public Overloads Sub Add(item As String)
        MyBase.Add(item)
        RaiseEvent ItemAdded(Me, item)
    End Sub

End Class

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AlyantoAuthor Commented:
Is there a way to make this more generic, I can see from the code that it will only be a list of string.

Would it be possible to
                 
 Public Class MyCustomList
    Inherits Generic.List(Of T)

    Public Sub New()
        MyBase.New()
    End Sub

    Public Event ItemAdded(ByRef sender As List(Of String), ByRef item As String)

    Public Overloads Sub Add(item As String)
        MyBase.Add(item)
        RaiseEvent ItemAdded(Me, item)
    End Sub

End Class

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perhaps?
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CodeCruiserCommented:
Can you describe what you are trying to achieve?
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AlyantoAuthor Commented:
In the very simplest sense I am trying to improve generic.list or similar so that when something is added or deleted from the list an event fires.  

This is a generic piece of code with no specific goal but has a general application.
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CodeCruiserCommented:
right. Does following work in making it generic?

 Public Class MyCustomList
    Inherits Generic.List(Of T)

    Public Sub New()
        MyBase.New()
    End Sub

    Public Event ItemAdded(ByRef sender As List(Of T), ByRef item As T)

    Public Overloads Sub Add(item As T)
        MyBase.Add(item)
        RaiseEvent ItemAdded(Me, item)
    End Sub

End Class

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AlyantoAuthor Commented:
Excellent, thank you.

/Aly
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