如何在vb.net中使用vb6的新集合

Question

I am converting vb6 project to vb.net but have stuck on these

Private mCol As Collection

Public Property Get NewEnum() As IUnknown
    'this property allows you to enumerate
    'this collection with the For...Each syntax
    Set NewEnum = mCol.[_NewEnum]
End Property

Private Sub Class_Initialize()
    'creates the collection when this class is created
    Set mCol = New Collection
End Sub

I am new to vb.net so I don't have any knowledge about working on these codes.Can someone please explain me its working and how can I code it in vb.net

This is the vb6 function for collection

Public Function Add(Key As String, Optional sKey As String) As clsUser_Rights
    'create a new object
    Dim objNewMember As clsUser_Rights
    Set objNewMember = New clsUser_Rights

    'set the properties passed into the method
    objNewMember.Key = Key
    If Len(sKey) = 0 Then
        mCol.Add objNewMember
    Else
        mCol.Add objNewMember, sKey
    End If

    'return the object created
    Set Add = objNewMember
    Set objNewMember = Nothing
End Function

and this is what I tried

Private mCol As New Dictionary(Of string,string)

Public Function Add(Key As String, Optional sKey As String = "") As clsMsmt
    'create a new object
    Dim objNewMember As clsMsmt
    objNewMember = New clsMsmt

    'set the properties passed into the method
    objNewMember.Key = Key
    If sKey.Length = 0 Then
        mCol.Add(objNewMember)
    Else
        mCol.Add(objNewMember, sKey)
    End If

    'return the object created
    Add = objNewMember
    objNewMember = Nothing
End Function

Answer 1

The VB6 code that you highlighted looks like a custom wrapper class for the built-in Collection type. The enumerator part is to allow For Each ... Next on the custom collection.

Depending on the purpose of the collection class, you might not need it in .NET. One reason why custom collection classes were made in VB6 was to provide type safety, since Collection would only provide Object . For this use, you can use either List (Of T) or Dictionary (Of TKey, TValue) depending on how the collection was used.

If there is additional logic in the collection, you might still stick with the framework classes and add one or more extension methods to handle the additional logic, or you might inherit from Collection (Of T) or KeyedCollection (Of TKey, TItem) . The base classes will provide the collection boilerplate logic, and you can focus on providing the additional logic in your inherited class.

If the code that used the VB6 collection was indexed by both string and integer, then you might need to do a little more legwork to get a working .NET equivalent, but I wouldn't tend to expect this (and even if it was done, the most likely use case might have been for removing items, and you could rewrite that to work correctly with a string-indexed .NET dictionary).

Answer 2

did you try google your question first? I think you did not. But anyway, here is a hint:

' wrong: Dim mCcol As New Microsoft.VisualBasic.Collection()  

' correct: 
Dim mCcol As New Collection()  

sorry, tried it in C# first, and in VB.NET this assembly is referenced by default.

Added new sample (in empty WinForm:)

    Dim dict As New Dictionary(Of String, String)
    dict.Add("KEY1", "dict: Some kind of stringdata")
    dict.Add("KEY2", "dict: other string data")
    dict.Add("KEY3", "dict: and finally: a string")

    For Each s As KeyValuePair(Of String, String) In dict
        MessageBox.Show(s.Value)
    Next

Replace the second String in the definition with your type (clsMsmt)