How to set a color for a rectangle?

Question

I had drawn a rectangle by adding element to graphics container like the code below:

IGraphicsContainer gc = mxDoc.FocusMap as IGraphicsContainer;
gc.Reset();
IRectangleElement rectangleElement = new RectangleElementClass();
IElement elem = rectangleElement as IElement;
gc.AddElement(elem, 0);

I want to remove the color from the rectangle or set the Transparency by 100, and keep the outline colored as it is.

Answer 1

QI/cast from your rectangle element to IFillShapeElement and set its Symbol.Color property to IColor.NullColor.