Removing a Specific Item from Array

[digitaldrew]

Hey everyone..I could really use some help with removing a specific item from an array. Here is what I have so far..

Right now I have two arrays. The first array holds a list of domain names that will be checked to see if they are available for registration. If one or more of those domains is available then they will be put into a second array and sent over to get registered. Once the domains in the second array are successfully registered I want to remove them from the first array so they are not checked for availability again (since I've just registered them)..

My current code is suppose to copy the main array (with all domains) to a temporary array - remove the registered domain(s) from the second array and then copy that temporary array (now with removed elements) back over to the main array so it can start from the beginning. The problem is, it doesn't actually remove the correct elements..It simply removes the last domain in the array. What this means, is that if I check a list of 5 domains and the domain in position 3 gets registered - it won't remove it from the array. Instead, the domain in the last position will be removed.

    Public Sub ArrayCompare()
        Dim tmpcnt As Integer
        Dim cnt1 As Integer
        Dim cnt3 As Integer
        Dim cnt4 As Integer

        cnt1 = 0
        cnt3 = 0
        cnt4 = 0
        'Find the location of the registered domains in the main array
        tmpcnt = registeredArray.Length
        While cnt3 <= mainArray.Length - 1
            'here it checks the mainArray to see if it containts the registeredArray domain
            While cnt4 <= availablecnt
                If InStr(mainArray(cnt3), registeredArray(cnt4)) = 0 Then
                    'do nothing
                ElseIf InStr(mainArray(cnt3), registeredArray(cnt4)) > 0 Then
                    TempArray1 = mainArray
                    RemoveItem2()
                    mainArray = TempArray1
                    If tmpcnt = 1 Then
                        Exit Sub
                    End If
                Else
                    txtLog.AppendText("Error With ArrayCompare: " & registeredArray(cnt4) & vbCrLf)
                End If
                cnt4 = cnt4 + 1
            End While
            cnt4 = 0
            cnt3 = cnt3 + 1
        End While
        ReDim Preserve mainArray(UBound(mainArray) - 1)

    End Sub

and

    Public Sub RemoveItem2()
        Dim TempDelElement As String
        For Me.cnt2 = 0 To DeleteArray.Length - 1
            TempDelElement = DeleteArray(cnt2)
            cnt1 = 0
            While cnt1 < TempArray1.Length - 1
                If TempDelElement = TempArray1(cnt1) Then
                    RemoveElement()
                End If
                cnt1 = cnt1 + 1
            End While
        Next
    End Sub

and

    Public Sub RemoveElement()
        Dim I As Integer
        For I = cnt1 To UBound(TempArray1) - 1
            TempArray1(I) = TempArray1(I + 1)
        Next I
    End Sub

[Niya]

I have a suggestion that would make all this 100x simpler. Use a List(Of T) instead of arrays. The List(Of T) has methods to remove elements from it. That code you posted is the kind of thing you'd do in VB6. You don't have to torture yourself like that in VB.Net.

[dunfiddlin]

You can't remove an element from the midst of an array because it's a fixed length object. If you redim it to fewer items than it will simply truncate. I admit I didn't attempt to follow the logic of your 'solution' but then I knew it wouldn't work already!

If you want to literally remove items then choose an object which has a Remove method; List, ListBox.Items etc.

[dunfiddlin]

That code you posted is the kind of thing you'd do in VB6.

It wouldn't have worked any better though. They ain't changed the specifications of arrays since ... well ... ever!

[Niya]

It wouldn't have worked any better though. They ain't changed the specifications of arrays since ... well ... ever!

Thing is though, in VB6 you had no choice. You could have opted to use the Collection class but that thing is so broken by trying to be a dictionary and a collection at the same time that its best to avoid it to preserve your sanity.

[digitaldrew]

I have a suggestion that would make all this 100x simpler. Use a List(Of T) instead of arrays. The List(Of T) has methods to remove elements from it. That code you posted is the kind of thing you'd do in VB6. You don't have to torture yourself like that in VB.Net.

The registrar requires domains be sent in an array..not a List.

Thanks for the input everyone!

[Niya]

The registrar requires domains be sent in an array..not a List.

Doesn't much a difference. An array can be converted to a List(Of T) by calling its ToList method. You can convert the arrays to lists, remove, add etc to it and you can convert the list or lists back into arrays by calling ToArray.

[digitaldrew]

Doesn't much a difference. An array can be converted to a List(Of T) by calling its ToList method. You can convert the arrays to lists, remove, add etc to it and you can convert the list or lists back into arrays by calling ToArray.

Thanks for the suggestion. I'll look into this.

[AceInfinity]

Manage the data in a List(of T) as mentioned, and when you are ready to send it in, cast it to an array with the ToArray() method. Removing an element from an array and resizing it accordingly, or creating a new fixed sized array would be just a bunch of fooling around.