private void AdjustDepthCueing(View view)
{
    if (view.CanUseDepthCueing())
    {
        using (Transaction t = new Transaction(view.Document, "Change depth cueing"))
        {
            t.Start();
            ViewDisplayDepthCueing depthCueing = view.GetDepthCueing();
            depthCueing.EnableDepthCueing = true;
            depthCueing.FadeTo = 50;    // set fade to percent
            depthCueing.SetStartEndPercentages(0, 75);
            view.SetDepthCueing(depthCueing);
            t.Commit();
        }
    }
}

Private Sub AdjustDepthCueing(view As View)
    If view.CanUseDepthCueing() Then
        Using t As New Transaction(view.Document, "Change depth cueing")
            t.Start()
            Dim depthCueing As ViewDisplayDepthCueing = view.GetDepthCueing()
            depthCueing.EnableDepthCueing = True
            depthCueing.FadeTo = 50
            ' set fade to percent
            depthCueing.SetStartEndPercentages(0, 75)
            view.SetDepthCueing(depthCueing)
            t.Commit()
        End Using
    End If
End Sub