根据文件字节大小格式化文件空间大小

 /// <summary>
        /// 格式化文件大小
        /// </summary>
        /// <param name="size">大小</param>
        /// <returns>式化大小</returns>
        public string FormatSize(long size)
        {
            try
            {
                string strReturn = "";
                double tempSize = Math.Abs(size);
                if (tempSize < 1024)
                {
                    strReturn += tempSize.ToString() + "B";
                }
                else if (tempSize < 1024 * 1024)
                {
                    tempSize = tempSize / 1024;
                    strReturn += tempSize.ToString("0.##") + "K";
                }
                else if (tempSize < 1024 * 1024 * 1024)
                {
                    tempSize = tempSize / 1024 / 1024;
                    strReturn += tempSize.ToString("0.##") + "M";
                }
                else
                {
                    tempSize = tempSize / 1024 / 1024 / 1024;
                    strReturn += tempSize.ToString("0.##") + "G";
                }

                if (size < 0)
                {
                    strReturn = "-" + strReturn;
                }

                return strReturn;
            }
            catch (Exception e)
            {
                throw e;
            }
            
        }