/// <summary>

        /// 将前端传来的dataurl转成图片并返回文件地址

        /// </summary>

        /// <param name="dataUrl"></param>

        /// <returns></returns>

        public  string SaveImageDataUrlToFileAndReturnFilePath(string dataUrl)

        {

            string fileinfo = StringCutCharBefore(dataUrl,';');

            string fileExtend = StringCutCharAfter(fileinfo, '/');

            if (!Directory.Exists(HttpContext.Current.Server.MapPath("/upload/image")))

            {

                Directory.CreateDirectory(HttpContext.Current.Server.MapPath("/upload/image"));

            }

            //if (fileExtend == "jpeg") { fileExtend = "jpg"; }



            string filename = HttpContext.Current.Server.MapPath(String.Format("/upload/image/{0}.{1}", Guid.NewGuid().ToString(), fileExtend));



            byte[] arrb =  Convert.FromBase64String(StringCutCharAfter(dataUrl,','));

            MemoryStream stream = new MemoryStream(arrb);

            StreamToFile(stream, filename);



            return filename;

        }

        public string StringCutCharBefore(string str,char c)

        {

            var index = str.IndexOf(c);

            return str.Substring(0, index);

            

        }

        public string StringCutCharAfter(string str, char c)

        {

            return str.Substring(str.IndexOf(c) + 1);

        }

public void StreamToFile(Stream stream, string fileName)

        {



            // 把 Stream 转换成 byte[] 



            byte[] bytes = new byte[stream.Length];



            stream.Read(bytes, 0, bytes.Length);



            // 设置当前流的位置为流的开始 



            stream.Seek(0, SeekOrigin.Begin);



            // 把 byte[] 写入文件 



            FileStream fs = new FileStream(fileName, FileMode.Create);



            BinaryWriter bw = new BinaryWriter(fs);



            bw.Write(bytes);



            bw.Close();



            fs.Close();



        }