net中c#教程 network的常用操作，包括上传、下载

现在互联网这么发达，我们做的项目也是需要从网络上获取信息（即下载数据），或者将本地的数据上传到服务器上（即上传数据）。所以，对网络的操作也很重要和基础，今天分享的教程，就是关于网络编程（network）的，就是https://这个串。

1、获取Url地址的前缀

这个方法主要用于判断主机？比如是服务器调用，还是本机localhost测试？

string urlPath = "https://webapi.navisoft.com.cn/api/getUser?userCode=vincent.q";
string urlPrefix = UrlHelper.GetUrlPrefix(urlPath);     //结果:https://webapi.navisoft.com.cn/api/getUser

2、获取Url的参数部分

就是获取?后面的参数，根据参数值执行不同的业务逻辑

string urlPath1 = "https://webapi.navisoft.com.cn/api/getUser?userCode=vincent.q";
Dictionary<string, string> dicP1 = UrlHelper.GetUrlParam(urlPath1);
string json1 = JsonHelper.GetJsonByObject(dicP1);       //结果:{"userCode":"vincent.q"}

3、组装Url的参数部分

不需要我们再StringBuilder的拼接了，直接使用键值对即可

Dictionary<string, string> dicP2 = new Dictionary<string, string>();
dicP2.Add("code", "1001");
dicP2.Add("name", "小Q");
dicP2.Add("sex", "male");
dicP2.Add("year", "40");
string urlP2 = UrlHelper.ComboUrlParam(dicP2);          //结果:code=1001&name=小Q&sex=male&year=40

4、获取分页页数

获取的数据量很大时，需要用到分页来优化性能。这个方法用来确定分页？即根据每页多少数据确定需要分多少页

int pageSize = 1000;
long totalCount = 12345;
List<long> listPage = UrlHelper.GetPageParam(totalCount, pageSize); //结果:共有13页

5、Encode和Decode加密和解密

第三方的开放平台，一般都需要这样。尤其是中文参数较多的时候

string urlP21 = UrlHelper.UrlEncode(urlP2);     //结果:code%3d1001%26name%3d%e5%b0%8fQ%26sex%3dmale%26year%3d40
string urlP22 = UrlHelper.UrlDecode(urlP21);    //结果:code=1001&name=小Q&sex=male&year=40

6、下载方法

要看下载的是什么类型的数据？比如是二进制、字符串、还是图片

string byteUrl = null;
byte[] bytes1 = UrlHelper.DownloadData(byteUrl);

string imageUrl = null;
System.Drawing.Image image = UrlHelper.DownloadImage(imageUrl);

string fileUrl = null;
string localFile = null;
UrlHelper.DownloadFile(fileUrl, localFile);

7、任意的上传下载方法

这2个方法之前也分享过，这里再分享一次。不同之处是增加了Post流数据的方法

/// <summary>
/// 提交GET方法至指定的Url,解析返回的数据
/// </summary>
/// <param name="url"></param>
/// <param name="charset"></param>
/// <returns></returns>
[ShortDescription("根据Get方式请求URL下载数据")]
public static string WebMethodGetData(string url, string charset = "utf-8")
{
    WebResponse response = null;
    Stream receiveStream = null;

    try
    {
        WebClientEx wc = new WebClientEx();
        byte[] byteResponse = wc.DownloadData(url);
        wc.Dispose();   //及时释放、避免第二次下载时、奇怪的"操作超时"的问题

        //字符集为UTF8
        string responseStr = Encoding.GetEncoding(charset).GetString(byteResponse);
        return responseStr;
    }
    catch (WebException ex)
    {
        string errorMessage = ex.Message;

        //需判断response是否==null
        response = ex.Response;
        if (response == null)
        {
            dynamic objErrorData = new { message = errorMessage, subErrors = "" };
            string jsonErrorData = JsonHelper.GetJsonByObject(objErrorData);
            //throw new CustomApiJsonException(jsonErrorData, url, ex);
            throw ex;
        }
        else
        {
            receiveStream = response.GetResponseStream();
            Encoding encode = Encoding.GetEncoding(charset);
            StreamReader sr = new StreamReader(receiveStream, encode);
            char[] readbuffer = new char[2048];
            int n = sr.Read(readbuffer, 0, 2048);

            string result = string.Empty;
            while (n > 0)
            {
                string str = new string(readbuffer, 0, n);
                result += str;
                n = sr.Read(readbuffer, 0, 2048);
            }
            response.Close();

            //此处将错误信息和json信息同时返回
            dynamic objErrorData = new { message = errorMessage, subErrors = result };
            string jsonErrorData = JsonHelper.GetJsonByObject(objErrorData);

            //throw new CustomApiJsonException(jsonErrorData, url, ex);
            throw ex;
        }
    }
    finally
    {
        //使用完后、释放资源
        if (response != null) response.Close();
        if (receiveStream != null) receiveStream.Close();
    }
}

/// <summary>
/// 提交POST方法至指定的Url,解析返回的数据
/// 参考地址:http://www.cnblogs.com/teikey/p/3373882.html
/// </summary>
/// <param name="url"></param>
/// <param name="requestParam"></param>
/// <param name="charset"></param>
/// <param name="contentType"></param>
/// <param name="dicHeader"></param>
/// <returns></returns>
[ShortDescription("根据Post方式请求URL下载数据")]
public static string WebMethodPostData(string url, string requestParam, string charset = "utf-8", string contentType = "application/x-www-form-urlencoded",Dictionary<string,string>dicHeader=null)
{
    WebRequest hr = null;
    WebResponse response = null;
    Stream receiveStreamIn = null;
    Stream receiveStreamOut = null;
    StreamReader srIn = null;
    StreamReader srOut = null;

    try
    {
        //创建访问对象
        hr = HttpWebRequest.Create(url);
        hr.Timeout = requestTimeOut;

        //拼接参数
        byte[] buf = System.Text.Encoding.GetEncoding(charset).GetBytes(requestParam);
        //hr.ContentType = "application/x-www-form-urlencoded";
        hr.ContentType = contentType;
        hr.ContentLength = buf.Length;
        hr.Method = "POST";

        if (dicHeader != null)
        {
            foreach (string sKey in dicHeader.Keys)
            {
                string sValue = dicHeader[sKey];

                hr.Headers.Add(sKey, sValue);
            }
        }

        System.IO.Stream RequestStream = hr.GetRequestStream();
        RequestStream.Write(buf, 0, buf.Length);
        RequestStream.Close();

        response = hr.GetResponse();
        receiveStreamIn = response.GetResponseStream();
        Encoding encode = Encoding.GetEncoding(charset);
        srIn = new StreamReader(receiveStreamIn, encode);
        char[] readbuffer = new char[2048];
        int n = srIn.Read(readbuffer, 0, 2048);

        string result = string.Empty;
        while (n > 0)
        {
            string str = new string(readbuffer, 0, n);
            result += str;
            n = srIn.Read(readbuffer, 0, 2048);
        }
        response.Close();   //注:此处用完以后立即关闭

        //如果未取得Json数据，则抛出异常
        if (string.IsNullOrEmpty(result))
        {
            //throw new CustomApiException("消息长度：" + response.ContentLength + "消息内容：" + response.ToString(), url);
            List<string> listEx = new List<string>();
            listEx.Add("消息长度：" + response.ContentLength);
            listEx.Add("消息内容：" + response.ToString());
            listEx.Add("Url地址：" + url);
            string exs = string.Join(Environment.NewLine, listEx);
            throw new Exception(exs);
        }

        return result;
    }
    catch (WebException ex)
    {
        string errorMessage = ex.Message;

        //需判断response是否==null
        response = ex.Response;
        if (response == null)
        {
            dynamic objErrorData = new { message = errorMessage, subErrors = "" };
            string jsonErrorData = JsonHelper.GetJsonByObject(objErrorData);

            //throw new CustomApiJsonException(jsonErrorData, url + "?" + requestParam, ex);
            throw ex;
        }
        else
        {
            receiveStreamOut = response.GetResponseStream();
            Encoding encode = Encoding.GetEncoding(charset);
            srOut = new StreamReader(receiveStreamOut, encode);
            char[] readbuffer = new char[2048];
            int n = srOut.Read(readbuffer, 0, 2048);

            string result = string.Empty;
            while (n > 0)
            {
                string str = new string(readbuffer, 0, n);
                result += str;
                n = srOut.Read(readbuffer, 0, 2048);
            }
            response.Close();

            //此处将错误信息和json信息同时返回
            dynamic objErrorData = new { message = errorMessage, subErrors = result };
            string jsonErrorData = JsonHelper.GetJsonByObject(objErrorData);

            //throw new CustomApiJsonException(jsonErrorData, url + "?" + requestParam, ex);
            throw ex;
        }
    }
    finally
    {
        //http://www.cnblogs.com/huangtailang/archive/2013/07/09/3180651.html
        if (hr != null) hr.Abort();//中止请求
        hr = null;  //需要写下Null

        if (response != null) response.Close();
        if (receiveStreamIn != null) receiveStreamIn.Close();
        if (receiveStreamOut != null) receiveStreamOut.Close();
        if (srIn != null) srIn.Close();
        if (srOut != null) srOut.Close();

        System.GC.Collect();//强制垃圾回收,并释放资源
    }
}

/// <summary>
/// 生成图片流的字符串参数值(目前用于速卖通图片上传)
/// </summary>
/// <param name="url"></param>
/// <param name="stream"></param>
/// <param name="contentType"></param>
/// <returns></returns>
[ShortDescription("根据Post方式请求URL下载数据")]
public static string WebMethodPostData(string url, Stream stream, string contentType)
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
    request.Timeout = requestTimeOut;
    try
    {
        request.Method = "POST";
        request.Accept = "*/*";
        request.KeepAlive = true;
        request.ContentType = contentType;
        request.Credentials = System.Net.CredentialCache.DefaultCredentials;
        request.ContentLength = stream.Length;

        using (Stream requestStream = request.GetRequestStream())
        {
            //将内存流数据读取位置归零
            stream.Position = 0;
            byte[] tempBuffer = new byte[stream.Length];
            stream.Read(tempBuffer, 0, tempBuffer.Length);
            stream.Close();

            //将内存流中的buffer写入到请求写入流
            requestStream.Write(tempBuffer, 0, tempBuffer.Length);
            requestStream.Close();

            //获取到上传请求的响应
            WebResponse response = request.GetResponse();

            //获取到上传返回的数据
            StreamReader reader = new StreamReader(response.GetResponseStream(), System.Text.Encoding.UTF8);
            string content = reader.ReadToEnd();
            response.Close();
            request = null;

            return content;
        }
    }
    finally
    {
        if (request != null) request.Abort();//中止请求
        request = null;  //需要写下Null

        System.GC.Collect();//强制垃圾回收,并释放资源
    }
}

关于数据采集的常用操作，这里先抛个引子，强烈推荐HtmlAgilityPack这个组件，非常好用。各种XPath操作都支持，只要看得到的数据，都能采集到。下次我们详细讲下数据采集这块

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