Vb.net How to remove duplicates from an Array?

Question

Dim ItemList As New ArrayList()

For i = 0 To dgExtract.Items.Count - 1
        gRow = dgExtract.Items(i)
        chk = gRow.FindControl("chkSelect")
        If chk.Checked Then
            sEmail = gRow.Cells(7).Text
            dim number as string = Regex.Replace(sEmail,"[^0-9]","")
            if number.length = 11 then
                ItemList.Add(number)
            end if
        end if              
Next

I build up the ItemList array with the above code. How do i remove any duplicates in this array?

I wouldn't use an ArrayList ever (well, maybe there would be some strange situation where I would). Better to use a List(Of String) in this case. — Neverbirth
– Neverbirth, Commented May 31, 2011 at 9:39
Unfortunately, sometimes we are stuck supporting legacy code, i.e. .Net 1.1. — Roman
– Roman, Commented Aug 8, 2013 at 19:59

bluish · Accepted Answer · 2015-03-12 15:08:46Z

9

Setting:

Dim number As Integer
Dim num As String
Dim al As New ArrayList()
If Not (al.Contains(number)) Then
    al.Add(number)
End If

Getting:

For Each number In al
    num = number.ToString()
Next

edited Mar 12, 2015 at 15:08

bluish

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answered May 31, 2011 at 9:42

Saurabh

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Comments

bluish · Accepted Answer · 2015-03-12 15:11:19Z

5

Rather than checking and removing the duplicate elements you can check whether it is in the array, if it doesn't exist you can add to array, else do nothing.

Declare a List<string> object named for instance list. In the loop:

If Not list.Contains(number) Then
    list.Add(number)

edited Mar 12, 2015 at 15:11

bluish

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answered May 31, 2011 at 9:35

Srinivasan MK

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Comments

Neverbirth · Accepted Answer · 2011-05-31 09:36:07Z

4

You'd declare some array (or List, or whatever collection you may prefer) and would do something like:

Array.Resize(numberArray, numberArray.Length + 1)
numberArray[numberArray.Length - 1] = number

Then you could use LINQ:

numberArray.Distinct()

And then, iterate the array and do whatever you need.

EDIT: Better what Srinivasan__ said, check whether the item exists, and if it doesn't add it. To check for it, you can use Exists(). Or if using something like a List, Contains().

answered May 31, 2011 at 9:36

Neverbirth

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2 Comments

user4951 Over a year ago

Why is this not #1?

john k Over a year ago

Distinct is not a member of System.array

dhinesh · Accepted Answer · 2013-10-25 05:06:48Z

        int i;
        int j;
        int count = 0;
        int[] list = new int[5];
        //to add 5 data with duplicate
        list[0] = 1;
        list[1] = 5;
        list[2] = 2;
        list[3] = 4;
        list[4] = 5;
        #region toremovetheduplicate
        int c = 0, flag = 0;
        int[] list1 = new int[5];
        for (i = 0; i < list.Length; i++)
        {
            flag = 0;
            for (j = i + 1; j < list.Length; j++)
            {

                if (i != j)
                {
                    if (list[i] == list[j])
                    {
                        flag = 1;
                    }
                }
            }
            if (flag == 0)
            {
                list1[c] = list[i];
                c++;
            }
        }

user3144575 · Accepted Answer · 2013-12-29 20:19:54Z

I just saw this, I tried the following code ; it works fine, I'm using a CheckedListBox to view results. There 2 arraylist used. 'Darray' holding the original list of duplicated strings. Then, 'FinArray' to dump the non-duplicated strings, then display the 'FinArray' contents in the listbox:

    Sub CleanDupes()
    ' Clear listbox
    CheckedListBox1.Items.Clear()
    ' Create Final Array for non-duped data
    Dim FinArray As New ArrayList
    Dim InitFinarray, DarrayN, FinArrayN As String
    ' Add first record from original array into new array
    FinArray.Add(Darray.Item(0))
    InitFinarray = FinArray.Item(0)
    CheckedListBox1.Items.Add("Select/Unselect All")
    CheckedListBox1.Items.Add(InitFinarray)
    ' Loop into Orig Array and compare each record with strings in new array,
    ' if exist in new array, then skip, else add it
    For n As Integer = 0 To Darray.Count - 1
        DarrayN = Darray.Item(n)
        For n2 As Integer = 0 To FinArray.Count - 1
            If FinArray.Contains(DarrayN) Then
            Else
                FinArray.Add(DarrayN)
                FinArray.Sort(1, FinArray.Count - 1, Nothing)
            End If
        Next
    Next
    'Display New Non-Duped Array in listbox
    For n3 As Integer = 1 To FinArray.Count - 1
        CheckedListBox1.Items.Add(FinArray(n3))
    Next
     End Sub

bluish · Accepted Answer · 2015-03-12 15:11:56Z

0

Why don't you check like this

if number.length = 11 then
    if Not ItemList.contains(number)
        ItemList.Add(number)

edited Mar 12, 2015 at 15:11

bluish

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answered May 31, 2011 at 9:39

Developer

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