How to control duplicate data entry in a listview

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HI guys,
I used this code to check if the item added exists in the listview.but it's not working.can you take a quick look?

VB

Private Sub CheckDuplicates()
        Dim itemI As ListViewItem
        Dim itemJ As ListViewItem
        Dim ok As Integer

        For i As Integer = ListView1.Items.Count - 1 To 0 Step -1
            itemI = ListView1.Items(i)

            For j As Integer = i + 1 To ListView1.Items.Count - 1 Step 1
                itemJ = ListView1.Items(j)

                If itemI.SubItems(0).Text = itemJ.SubItems(0).Text AndAlso _
                   itemI.SubItems(1).Text = itemJ.SubItems(1).Text AndAlso _
                   itemI.SubItems(1).Text = itemJ.SubItems(2).Text AndAlso _
                   itemI.SubItems(1).Text = itemJ.SubItems(3).Text AndAlso _
                   itemI.SubItems(1).Text = itemJ.SubItems(4).Text AndAlso _
                   itemI.SubItems(1).Text = itemJ.SubItems(5).Text AndAlso _
                   itemI.SubItems(1).Text = itemJ.SubItems(6).Text AndAlso _
                   itemI.SubItems(1).Text = itemJ.SubItems(7).Text AndAlso _
                   itemI.SubItems(2).Text = itemJ.SubItems(8).Text Then
                    'Duplicate item found.
                    ok = MsgBox("A duplicate item is added,please remove the new item", vbCritical + vbOKCancel, _
                                 "Bridge Construction Cost Estimate")
                    If ok = vbOK Then
                        ListView1.Items.Remove(itemJ)
                    End If
                    Exit For
                End If
            Next j
        Next i
    End Sub

Posted 11-Nov-13 4:23am

Nebilo

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Mike Meinz · Answer 1 · 2013-11-11T04:30:00

There are several issues:

1. The SubItem index for itemI was not incremented. See below

VB

If itemI.SubItems(0).Text = itemJ.SubItems(0).Text AndAlso _
   itemI.SubItems(1).Text = itemJ.SubItems(1).Text AndAlso _
   itemI.SubItems(2).Text = itemJ.SubItems(2).Text AndAlso _
   itemI.SubItems(3).Text = itemJ.SubItems(3).Text AndAlso _
   itemI.SubItems(4).Text = itemJ.SubItems(4).Text AndAlso _
   itemI.SubItems(5).Text = itemJ.SubItems(5).Text AndAlso _
   itemI.SubItems(6).Text = itemJ.SubItems(6).Text AndAlso _
   itemI.SubItems(7).Text = itemJ.SubItems(7).Text AndAlso _
   itemI.SubItems(8).Text = itemJ.SubItems(8).Text Then
    'Duplicate item found.

2. When you Remove an item, the index number of all of the items with higher index numbers is decremented by one.

3. I am not sure about the second For statement. I would use this:

VB

For j As Integer = ListView1.Items.Count - 1 to 0 Step -1

4. Need to add a check to ensure you are not comparing the same entry to itself.

VB

If i<>j then
    If itemI.SubItems(0).Text = itemJ.SubItems(0).Text AndAlso _
       itemI.SubItems(1).Text = itemJ.SubItems(1).Text AndAlso _
       itemI.SubItems(2).Text = itemJ.SubItems(2).Text AndAlso _
       itemI.SubItems(3).Text = itemJ.SubItems(3).Text AndAlso _
       itemI.SubItems(4).Text = itemJ.SubItems(4).Text AndAlso _
       itemI.SubItems(5).Text = itemJ.SubItems(5).Text AndAlso _
       itemI.SubItems(6).Text = itemJ.SubItems(6).Text AndAlso _
       itemI.SubItems(7).Text = itemJ.SubItems(7).Text AndAlso _
       itemI.SubItems(8).Text = itemJ.SubItems(8).Text Then
       'Duplicate item found
       ok = MsgBox("A duplicate item is added,please remove the new item", vbCritical + vbOKCancel, _
           "Bridge Construction Cost Estimate")
       If ok = vbOK Then
          ListView1.Items.Remove(itemJ)
     End If
End If

Check for duplicate before adding an item to the ListView control.

VB

Dim itemJ As ListViewItem
Dim bFound As Boolean = False
For j As Integer = 0 To ListView1.Items.Count - 1
    itemJ = ListView1.Items(j)

    If payItem.ToString() = itemJ.SubItems(0).Text AndAlso _
       subpayItem.ToString() = itemJ.SubItems(1).Text AndAlso _
       subItem = itemJ.SubItems(2).Text AndAlso _
       unit = itemJ.SubItems(3).Text AndAlso _
       bridgeType = itemJ.SubItems(4).Text AndAlso _
       span = itemJ.SubItems(5).Text AndAlso _
       quantity.ToString() = itemJ.SubItems(6).Text AndAlso _
       Rate.ToString() = itemJ.SubItems(7).Text AndAlso _
       amount.ToString = itemJ.SubItems(8).Text Then
        'Duplicate item found.
        bFound = True
        Exit For
    End If
Next
If bFound Then
    Msgbox("Cannot add a duplicate item")
Else
    ListView1.Items.Add(payItem.ToString()).SubItems.AddRange({subpayItem.ToString(), subItem, unit, _
       bridgeType, span, quantity.ToString(), Rate.ToString(), amount.ToString()})
End If