How to scroll by one using mouse wheel instead of the default value ' 3 ' in Listview VB.net

Question

I have a modified list view (VB.net). When I scroll using the mouse wheel. It scrolls by 3 rows. I want it to scroll by one row at time using mouse wheel. Any help would be appreciate it.

Public Class listviewEx
Inherits ListView

Private Declare Function ShowScrollBar Lib "user32" (ByVal hwnd As IntPtr, ByVal wBar As Integer,
ByVal bShow As Boolean) As Integer
' Constants
Private Const SB_HORZ As Integer = 0

Private Const WM_HSCROLL As Integer = &H114
Private Const WM_VSCROLL As Integer = &H115

Public Event Scroll As ScrollEventHandler

Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
MyBase.WndProc(m)
ShowScrollBar(MyBase.Handle, SB_HORZ, False)
If m.Msg = &H115 Then
' Trap WM_VSCROLL
End If
End Sub

Public Sub New()
MyBase.New()
Me.SetStyle(ControlStyles.Opaque, True)
Me.SetStyle(ControlStyles.OptimizedDoubleBuffer, True)
Me.SetStyle(ControlStyles.ResizeRedraw, True)
Me.SetStyle(ControlStyles.AllPaintingInWmPaint, True)
Me.SetStyle(ControlStyles.EnableNotifyMessage, True)
End Sub

End Class

Answer 1

Check an approach:

Public Class listviewEx
    Inherits ListView

    Protected Overrides Sub WndProc(ByRef m As Message)

        Const WM_MOUSEWHEEL = &H20A

        Select Case m.Msg
            Case WM_MOUSEWHEEL
                If TopItem IsNot Nothing Then
                    Dim d As Int16 = m.WParam.ToInt32 >> 16
                    Dim i As Integer

                    If d > 0 Then
                        i = Math.Max(TopItem.Index - 1, 0)
                    Else
                        i = Math.Min(TopItem.Index + 1, Items.Count - 1)
                    End If

                    TopItem = Items(i)
                End If

                m.Result = IntPtr.Zero

                Return

        End Select

        MyBase.WndProc(m)

    End Sub

End Class