Sub test()
    Dim arr As Variant, brr As Variant, crr As Variant
    arr = Range(Cells(1, 1), Cells(Rows.Count, 1).End(xlUp)).Value
    brr = Range(Cells(1, 2), Cells(Rows.Count, 2).End(xlUp)).Value
    ReDim crr(UBound(arr) * UBound(brr))
    Dim i As Long, j As Long, k As Long
    For j = 1 To UBound(arr)
        For k = 1 To UBound(brr)
            crr(i) = arr(j, 1) & brr(k, 1)
            i = i + 1
        Next k
    Next j
    Cells(1, 3).Resize(UBound(crr) - 1).Value = Application.Transpose(crr)

Public Sub Test(ByVal ws As Worksheet)
    Dim arr As Variant
    arr = ws.Range(ws.Cells(1, 1), ws.Cells(ws.Rows.Count, 1).End(xlUp)).Value

    Dim brr As Variant
    brr = ws.Range(ws.Cells(1, 2), ws.Cells(ws.Rows.Count, 2).End(xlUp)).Value

    Dim crr As Variant
    ReDim crr(UBound(arr) * UBound(brr))

    Dim j As Long
    For j = 1 To UBound(arr)
        Dim k As Long
        For k = 1 To UBound(brr)
            Dim i As Long
            crr(i) = arr(j, 1) & brr(k, 1)
            i = i + 1

            foreach (var project in adding)
            {
                var model = new CodeExplorerProjectViewModel(project, ref updates, _state, _vbe) { Filter = Search };
                Projects.Add(model);
            }

    <TreeView x:Name="ProjectTree"
              Grid.Row="2"
              Background="White"
              HorizontalContentAlignment="Stretch"
              ItemsSource="{Binding Projects}"

?application.VBE.VBProjects.Count
 2

ActiveWorkbook.Worksheets(ActiveSheet.Name).{whatever}

Private Sub Foo()
    Debug.Print Bar(Sheet1)
End Sub

Public Function Bar(ByVal ws As Worksheet) As String
    Bar = ws.Name
End Function

?typename(sheet1)
Empty

?typeof sheet1 is worksheet
False