Dear Jassem,
<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
Thanks for considering Aspose.Slides
Please check this code and also see its output presentation outShadow.ppt attached by me.
C#:
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//Create a presentation
Presentation pres = new Presentation();
Slide sld = pres.GetSlideByPosition(1);
//Add a rectangle
Shape shp = sld.Shapes.AddRectangle(100, 100, 600, 600);
shp.FillFormat.Type = FillType.Solid;
shp.FillFormat.ForeColor = Color.Green; //Change it to white
//Add a shadow
ShadowFormat sf=shp.ShadowFormat;
sf.ShadowStyle = ShadowStyle.Style12;
sf.Visible = true;
//Write on disk
pres.Write("c:\\outShadow.ppt");