private void GetStairLandings(Stairs stairs)
{
    ICollection<ElementId> landingIds = stairs.GetStairsLandings();
    string info = "Number of landings:  " + landingIds.Count;

    int landingIndex = 0;
    foreach (ElementId landingId in landingIds)
    {
        landingIndex++;
        StairsLanding landing = stairs.Document.GetElement(landingId) as StairsLanding;
        if (null != landing)
        {
            info += "\nThickness of Landing " + landingIndex + ":  " + landing.Thickness;
        }
    }

    TaskDialog.Show("Revit", info);
}

Private Sub GetStairLandings(stairs As Stairs)
    Dim landingIds As ICollection(Of ElementId) = stairs.GetStairsLandings()
    Dim info As String = "Number of landings:  " & landingIds.Count

    Dim landingIndex As Integer = 0
    For Each landingId As ElementId In landingIds
        landingIndex += 1
        Dim landing As StairsLanding = TryCast(stairs.Document.GetElement(landingId), StairsLanding)
        If landing IsNot Nothing Then
            info += (vbLf & "Thickness of Landing " & landingIndex & ":  ") + landing.Thickness
        End If
    Next

    TaskDialog.Show("Revit", info)
End Sub