C# POST数据base64到接口会出错的问题

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这个base64在requestHeader里面变成了
base64=hySGNg22yX0AIjNQvNJw0xHEbi32NH%2BiRVKDkbOmUiKpxW0%2FS6rUgfLmSa527Y8zZ3GmEzfXMB8ry8fH5GjGeJFGqFxDC4A2hLlvIFzyiDeUCqloGDAJoOLa8Jnif1C8nwRte0GNCRM5RXkshLKZP2itZclgDCYz6OgAF7oLNluoB44cZ3AgF1Q8hVgME8LeqgOqxsIzTt3Xn%2B96j7zp%2FwA%3D

他把base64里面一些/和= 给转成%2F之类的东西了。

所以webservice接收到的参数是错的。。

解决办法：

string base64 = "base64=hySGNg22yX0AIjNQvNJw0xHEbi32NH+iRVKDkbOmUiKpxW0/S6rUgfLmSa527Y8zZ3GmEzfXMB8ry8fH5GjGeJFGqFxDC4A2hLlvIFzyiDeUCqloGDAJoOLa8Jnif1C8nwRte0GNCRM5RXkshLKZP2itZclgDCYz6OgAF7oLNluoB44cZ3AgF1Q8hVgME8LeqgOqxsIzTt3Xn+96j7zp/wA=";

byte[] buffer = Convert.FromBase64String(base64);

string Base64StrData = Convert.ToBase64String(buffer).Replace("+", "%2B");//注意加号（’+‘）的替换处理，否则由于加号经过Url传递后变成空格而得不到合法的Base64字符串

        string postData = "str=" + Base64StrData;

    byte[] dataArray = Encoding.Default.GetBytes(postData);

/// <summary>

        /// POST请求与获取结果

        /// </summary>

        public static string HttpPost(string Url, string postDataStr)

        {

            try

            {

                postDataStr = postDataStr.Replace("+", "%2B");

                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);

                request.Method = "POST";

                request.Timeout = ;

                request.ContentType = "application/x-www-form-urlencoded";

                request.ContentLength = postDataStr.Length;

                StreamWriter writer = new StreamWriter(request.GetRequestStream(), Encoding.ASCII);

                writer.Write(postDataStr);

                writer.Flush();

                HttpWebResponse response = (HttpWebResponse)request.GetResponse();

                string encoding = response.ContentEncoding;

                if (encoding == null || encoding.Length < )

                {

                    encoding = "UTF-8"; //默认编码

                }

                StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding(encoding));

                string retString = reader.ReadToEnd();

                return retString;

            }

            catch (Exception ex)

            {

                return null;

            }

        }