panel1.HorizontalScroll.Value cannot be set

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C#

Visual-Studio

.NET4

private void panel1_MouseWheel(object sender, MouseEventArgs e)
{
    if (sCDLST.Count > 0)
    {
        float z = Z;
        if (e.Delta > 0 && Z < 4) z += 0.1f;
        else if (e.Delta < 0 && Z > 1) z -= 0.1f;
        if (z != Z)
        {
            X = ((e.X + panel1.HorizontalScroll.Value) * z / Z - e.X);
            Z = z;
            Draw();
            panel1.AutoScrollMinSize = new Size((int)(bMP1.Width), 0);
            if (X < panel1.HorizontalScroll.Minimum) panel1.HorizontalScroll.Value = panel1.HorizontalScroll.Minimum;
            else if (X > panel1.HorizontalScroll.Maximum) panel1.HorizontalScroll.Value = panel1.HorizontalScroll.Maximum;
            else panel1.HorizontalScroll.Value = (int)X; //Problem : always zero
        }
    }
}

z:      new zoom factor
Z:      old zoom factor
Draw(): Redraw bMP1 based on new zoom factor

Hello everybody!

Here is the code that when user rotates the mouse wheel, "fixed-zoom in/out" will be performed. Then it will redraw the bitmap according to the new factor. The problem is that I cannot update the panel1.HorizontalScroll.Value

Thanks!