AngleTextNote.cs

    public static double Angle(Autodesk.Revit.DB.TextNote textnote)
        {
            XYZ direction = textnote.UpDirection;
            XYZ coordinate = new XYZ(0, 1, 0);
            double angle = direction.AngleTo(coordinate) * 180 / Math.PI;
            double baseX = textnote.BaseDirection.X;
            double baseY = textnote.BaseDirection.Y;
            double upX = textnote.UpDirection.X;
            double upY = textnote.UpDirection.Y;
            if (baseX <= 0 && baseY >= 0 && upX >= 0 && upY >= 0) return angle;
            
            if (baseX >= 0 && baseY >= 0 && upX <= 0 && upY >= 0) return angle;
            
            if (baseX <= 0 && baseY >= 0 && upX <= 0 && upY <= 0) return angle;

            if (baseX <= 0 && baseY <= 0 && upX >= 0 && upY <= 0) return 360 - angle;

            if (baseX >= 0 && baseY <= 0 && upX >= 0 && upY >= 0) return 360- angle;
            
            return angle;
        }