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Gets or sets a value that represents the opacity of the gradient fill expressed as a percent.
This value indicates the transparency setting applied at the current gradient stop.
double Transparency { get; set; }
Property Transparency As Double
IShape shape = worksheet.Shapes.AddShape(AutoShapeType.Rectangle, 20, 20, 120, 80);
IFillFormat fill = shape.Fill;
fill.TwoColorGradient(GradientStyle.Horizontal, 1);
IGradientStop stop = fill.GradientStops[0];
double transparency = stop.Transparency;