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ArcObjects 10.3 Add Transparent Polygon to Map

Question asked by joshua.corcoran on Jul 20, 2015
Latest reply on Jul 22, 2015 by Hornbydd

Hi everyone. This is an issue I have been trying to tackle for a while and decided to reach out for help. I am creating an ESRI ArcGIS Desktop Add-In that allows the user to draw a polygon and then have it added to the map. I am able to capture the polygon and add it to the map, the issue is the transparency. Currently and by default it is 100% opacity and solid. I want to make it around 50% opacity so the user can see the data behind it.

 

Here is the code I have so far:

public static void AddPolygonToMap(IActiveView ActiveViewInstance, IGeometry NewGeo)
        {
            //Local Variable Declaration
            var fillShapeElement = default(IFillShapeElement);
            var element = default(IElement);
            var graphicsContainer = default(IGraphicsContainer);
            var simpleFilleSymbol = default(ISimpleFillSymbol);
            var newRgbColor = default(IRgbColor);
            var lineSymbol = default(ILineSymbol);


            //Use the IElement interface to set the Envelope Element's geo
            element = new PolygonElement();
            element.Geometry = NewGeo;


            //QI for the IFillShapeElement interface so that the symbol property can be set
            fillShapeElement = element as IFillShapeElement;


            //Create a new fill symbol
            simpleFilleSymbol = new SimpleFillSymbol();


            //Create a new color marker symbol of the color black;
            newRgbColor = new RgbColor();
            newRgbColor.Red = 0;
            newRgbColor.Green = 0;
            newRgbColor.Blue = 0;
            
            //Create a new line symbol so that we can set the width outline
            lineSymbol = new SimpleLineSymbol();
            lineSymbol.Color = newRgbColor;
            lineSymbol.Width = 2;


            //Setup the Simple Fill Symbol
            simpleFilleSymbol.Color = newRgbColor;
            simpleFilleSymbol.Style = esriSimpleFillStyle.esriSFSHollow;
            simpleFilleSymbol.Outline = lineSymbol;
            fillShapeElement.Symbol = simpleFilleSymbol;


            //QI for the graphics container from the active view allows access to basic graphics layer
            graphicsContainer = ActiveViewInstance as IGraphicsContainer;


            //Add the new element at Z order 0
            graphicsContainer.AddElement((IElement)fillShapeElement, 0);


            //Show the new graphic
            ActiveViewInstance.Refresh();
        }

 

I know that this is possible somehow and I am sure it's just a line or two missing but any help would be much appreciated.

 

V/r,

Josh

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