Webservice接收16进制字符串并保存相应的文件

今天ipad那面想做下webservice上传图片，我这面要做个测试的接口，用于测试

图片是以16进制的字符串传过来，并同时传进来文件名称，因为只是测试所以，最简单的写了一个

[WebMethod]
        public void UploadFile(string fs,string fileName)
        {
            byte[] baseBytes = Hex2ByteArr(fs.Replace(" ",""));
            FileStream f = new FileStream(Path.Combine(AppDomain.CurrentDomain.BaseDirectory,fileName),FileMode.OpenOrCreate,FileAccess.Write);
            BinaryWriter w = new BinaryWriter(f);
            w.Write(baseBytes);
            w.Flush();
            f.Close(); 
            
        }

public byte[] Hex2ByteArr(string newString)
        {
            int len = newString.Length / 2;
            byte[] arr = new byte[len];
            for (int i = 0; i < len; i++)
            {
                arr[i] = Convert.ToByte(newString.Substring(i * 2,2),16);
            }
            return arr;
        }