OfficeOpenXml.ExcelHeaderFooterText.ValidateImage C# (CSharp) Method

        private string ValidateImage(PictureAlignment Alignment)
        {
            string id = string.Concat(Alignment.ToString()[0], _hf);
            foreach (ExcelVmlDrawingPicture image in _ws.HeaderFooter.Pictures)
            {
                if (image.Id == id)
                {
                    throw (new InvalidOperationException("A picture already exists in this section"));
                }
            }
            //Add the image placeholder to the end of the text
            switch (Alignment)
            {
                case PictureAlignment.Left:
                    LeftAlignedText += ExcelHeaderFooter.Image;
                    break;
                case PictureAlignment.Centered:
                    CenteredText += ExcelHeaderFooter.Image;
                    break;
                default:
                    RightAlignedText += ExcelHeaderFooter.Image;
                    break;
            }
            return id;
        }