revit api calculate area in csharp

main.cs
// Get the selected element
UIDocument uiDoc = commandData.Application.ActiveUIDocument;
Document doc = uiDoc.Document;
Reference reference = uiDoc.Selection.PickObject(ObjectType.Element);

// Get the geometry of the element
Element element = doc.GetElement(reference);
GeometryElement geometryElement = element.get_Geometry(new Options());

// Calculate the area of the element
double area = 0;
foreach (GeometryObject geometryObject in geometryElement)
{
    Solid solid = geometryObject as Solid;
    if (solid != null && solid.Volume > 0)
    {
        // Convert the units to square feet
        area += UnitUtils.ConvertFromInternalUnits(solid.SurfaceArea, DisplayUnitType.DUT_SQUARE_FEET);
    }
}

// Display the area in a dialog box
TaskDialog.Show("Area", "The area of the selected element is " + area + " sq. ft.");
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