For each loop, compare to next item on the list - vb.net

Question

I am writing an application where I bring change history of items from the database and place them on the table using For Each loop. I would, however, like to show in table what information has changed in each edit. Is it possible to compare variables of each item to the variables of next loop in For Each loop?
Something like:
For Each k As Examplemodel In Model
'Find next item on the loop after current one somehow
Dim nextItem = Model.Item(k+1) 'something like this
If k.ItemsName <> nextItem.Itemsname 'if the name has changed in edit
'show result in bold
Else
'show result in normal font weight
End If
Next
Is this possible and if not, what's the best way to achieve this?

Answer 1

You can't do it in a foreach loop directly.
If your Model class have indexers you can easily convert it into a for loop:
If Model.Count > 1 Then
For i as Integer = 0 to Model.Count - 2 ' Note the -2 here !!!
Dim Item As Examplemodel = Model(i)
Dim NextItem As Examplemodel = Model(i + 1)
if Item.ItemsName <> NextItem.ItemsName then
'show result in bold
else
'show result in normal font weight
end if
Next
'show result of NextItem here, since the last item doesn't get shown in the loop
Else
'show result of only item here
End If
If not, you can use a workaround like this:
Dim PrevItem as Examplemodel = Nothing ' Assuming a reference type
For Each k As Examplemodel In Model
If Not IsNothing(PrevItem) AndAlso k.ItemsName <> Prev.Itemsname 'if the name has changed in edit
'show result (of PrevItem!!!) in bold
Else
'show result (of PrevItem!!!) in normal font weight
End If
PrevItem = k
Next
'show result (of PrevItem (currently the last item in Model) in normal font weight

Answer 2

You should use a normal for loop:
Dim numbers() As Integer = New Integer() {1, 2, 4, 8}
Sub Main()
For index As Integer = 0 To numbers.Length - 2
Dim currentInt As Integer = numbers(index)
Dim nextInt As Integer = numbers(index + 1)
Console.WriteLine(currentInt)
Console.WriteLine(nextInt)
Next
End Sub

Answer 3

Another approach to use LINQ Aggregate extension method, which use first item of collection as initial value. So every item will have access to previous one.
Public Class ItemChanges
Public Property Item As ExampleModel
Public Property Changes As New Hash(Of String)
End Class
Public Function Check(previous As ItemChanges, current As ItemChanges) As ItemChanges
If current.Item.Name <> previous.Item.Name Then
current.Changes.Add(Nameof(current.Name))
End
Return current
End Function
' assume model is collection of items
Dim itemWithChanges =
model.Select(Function(m) New ItemChanges With { .Item = m })
.Aggregate(AddressOf(Check))
.ToList()
Then you can use calculated result as you want - every item will have a hash of property names which had changed
If checkedItem.Changes.Contains(Nameof(checkedItem.Item.Name)) Then
' use bold font or different color
End