网络数据请求request

关于网络数据请求的类很多，httpwebrequest，webrequest，webclient以及httpclient，具体差别在此不在赘述，在应用方面介绍webclient与httpclient则显得比较比较简单粗暴，httpwebrequest继承自webrequest，可通过参数进行请求控制。

1）基于WebClient的post/get数据请求：

get

            using (var client = new WebClient())
            {
                client.Encoding = Encoding.GetEncoding("utf-8");
                var responseString = client.DownloadString("http://www.sojson.com/open/api/weather/json.shtml?city=闵行区");
     
                Console.WriteLine(responseString);
                Console.ReadKey();
            }

post

            using (var client = new WebClient())
            {
                client.Encoding = Encoding.GetEncoding("utf-8");
                var values = new NameValueCollection();
                values["api_key"] = "**********";
                values["api_secret"] = "**********";
                values["image_url"] = "https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1508759666809&di=b3748df04c5e54d18fe52ee413f72f37&imgtype=0&src=http%3A%2F%2Fimgsrc.baidu.com%2Fimgad%2Fpic%2Fitem%2F562c11dfa9ec8a1389c45414fd03918fa1ecc06c.jpg";

                var response = client.UploadValues("https://api-cn.faceplusplus.com/facepp/v3/detect", values);

                var responseString = Encoding.Default.GetString(response);
                Console.WriteLine(responseString);
                Console.ReadKey();
            }

 2）基于HttpWebRequest 的get/post方法

get

  /// <summary>
        /// get
        /// </summary>
        /// <param name="url">url="http:**********"+"?"+"key1=***&key2=***"</param>
        /// example :http://www.sojson.com/open/api/weather/json.shtml?city=闵行区
        /// <returns></returns>
        public static string GetHttp(string url)
        {
            HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url);

            httpWebRequest.ContentType = "application/json";
            httpWebRequest.Method = "GET";
            httpWebRequest.Timeout = 20000;

            HttpWebResponse httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();
            StreamReader streamReader = new StreamReader(httpWebResponse.GetResponseStream());
            string responseContent = streamReader.ReadToEnd();

            httpWebResponse.Close();
            streamReader.Close();

            return responseContent;
        }

post

post提交数据的方式有四种，具体体现在contentType有四种方式：application/x-www-form-urlencoded，multipart/form-data，application/json以及text/xml，本文主讲前两种方法，第三种即为通过json格式发送数据，第四种通过xml格式发送。

（一）contentType=application/x-www-form-urlencoded

此种方式应用比较普遍，但是当传递参数中存在文件如图片时则需要用到multipart/form-data方式

       /// <summary>
        /// 采用httpwebrequest post方法请求数据
        /// </summary>
        /// <param name="url"></param>
        /// <param name="body">body是要传递的参数,格式:api_keyi=xxxxxx&api_secret=xxxxxxx</param>
        /// <param name="contentType">application/x-www-form-urlencoded</param>
        /// <returns></returns>
        public static string PostHttpWebRequest(string url, string body, string contentType)
        {
            HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url);

            httpWebRequest.ContentType = contentType; 
            httpWebRequest.Method = "POST";
            httpWebRequest.Timeout = 1000;

            byte[] btBodys = Encoding.UTF8.GetBytes(body);
            httpWebRequest.ContentLength = btBodys.Length;
            httpWebRequest.GetRequestStream().Write(btBodys, 0, btBodys.Length);

            HttpWebResponse httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();
            StreamReader streamReader = new StreamReader(httpWebResponse.GetResponseStream());
            string responseContent = streamReader.ReadToEnd();

            httpWebResponse.Close();
            streamReader.Close();
            httpWebRequest.Abort();
            httpWebResponse.Close();

            return responseContent;
        }

（二）contentType=multipart/form-data

 此种方式请求数据时，请求的数据流比较繁琐，需要自己来确定，即httpWebRequest.GetRequestStream().Write(btBodys, 0, btBodys.Length);中的btBodys需要自己构造，比较繁琐。其构造主体如下所示：

HTTP请求头：
....
multipart/form-data; charset=utf-8;boundary=AaB03x //boundary=AaB03x为下文请求体中用于分隔不同请求参数的文本边界请求头可以放在请求数据流中，也可以直接在contentType中定义即contentType=multipart/form-data; charset=utf-8;boundary=AaB03x
....


HTTP请求体：
--AaB03x                                                                  //第一个参数边界：即在请求头中boundary文本AaB03x前加‘’--‘’
Content-Disposition: form-data; name="key1"         //换行，在此加入数据的第一个参数名称
                                                                                //继续换行（即空一行）
value1                                                                     //添加第一个参数对应的值
--AaB03x                                                                 //第二个参数边界：即在请求头中boundary文本AaB03x前加‘’--‘’，字符串参数格式均与上同
Content-disposition: form-data; name="key2"             

value2
--AaB03x                                                                  //边界，此处添加图片
Content-disposition: form-data; name="key3"; filename="file"    // filename表示文件名，其值与是否为真实文件名无关
Content-Type: application/octet-stream                   // 表示文件形式，这也是与字符串参数的不同

图片数据                                                                  // 图片数据，为二进制byte类型数据
--AaB03x--                                                               //结束边界，为boundary文本值AaB03x前后各加加‘’--‘’

PS:

1）边界boundary的值未不会重复的字符串，大小等因素基本没影响，一般采用boundary = string.Format("{0}", Guid.NewGuid());生成，或者采用时间参数如boundary =DateTime.Now.Ticks.ToString();

代码如下

    class RequestForm
    {
        public class PostImage  //image
        {
            public string fullPath;
            public string imageName; 
            public string contentType= "application/octet-stream";

            public PostImage(string path)
            {
                fullPath = path;
                imageName = Path.GetFileName(path);
            }            
        }

        class PostFile //files
        {

        }

        private static readonly Encoding encoding = Encoding.UTF8;


        /// <summary>
        /// 调用入口
        /// </summary>
        /// <param name="postParameter"></param>
        /// <param name="url"></param>
        /// <returns></returns>
        public static string OnRequest(Dictionary<string,object> postParameter,string url)//主调用程序
        {
            string boundary = string.Format("{0}", Guid.NewGuid());
            byte[] body=GetPostForm(postParameter, boundary);
            string contentType = "multipart/form-data; boundary=" + boundary;
            return OnWebRequest(body, url, contentType);
            //return PostForm(url, contentType, body);
        }

        private static byte[] GetPostForm(Dictionary<string, object> postParameter,string boundary)//获取请求主体
        {
            Stream stream = new MemoryStream();
            bool isFirstPara = false;        

            foreach (KeyValuePair<string, object> para in postParameter)
            {
                if (isFirstPara)
                {
                    stream.Write(encoding.GetBytes("
"), 0,encoding.GetByteCount("
"));
                }

                isFirstPara = true;
                //若需要添加文件信息如txt等增加else分支添加
                if (para.Value is PostImage)
                {
                    PostImage postImage = (PostImage)para.Value;                    
                    string imageStatement = string.Format("--{0}
Content-Disposition: form-data; name="{1}"; filename="{2}"
Content-Type: {3}

", new object[]
                    {
                        boundary,
                        para.Key,
                        postImage.imageName??para.Key,
                        postImage.contentType??"application/octet-stream"
                    });
                    stream.Write(encoding.GetBytes(imageStatement), 0, encoding.GetByteCount(imageStatement));
                    byte[] imageContent = GetImageInfo(postImage.fullPath);
                    stream.Write(imageContent, 0, imageContent.Length);
                }
                else
                {
                    string regularStatement = string.Format("--{0}
Content-Disposition: form-data; name="{1}"

{2}", boundary, para.Key, para.Value);
                    stream.Write(encoding.GetBytes(regularStatement), 0, encoding.GetByteCount(regularStatement));
                }
            }

            string end = "
--" + boundary + "--
";
            stream.Write(encoding.GetBytes(end), 0, encoding.GetByteCount(end));
            stream.Position = 0L;
            byte[] bodyArr = new byte[stream.Length];
            stream.Read(bodyArr, 0, bodyArr.Length);
            stream.Close();

            return bodyArr;
        }

        private static string OnWebRequest(byte[] postForm,string url,string contentType)//数据请求
        {
            HttpWebRequest request =(HttpWebRequest)WebRequest.Create(url);
            //try
            //{
            //    HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
            //}
            //catch(WebException ex)
            //{
            //    return ex.Message;
            //}

            if (request == null) return "Failed to connect url";
            request.Method = "POST";
            request.Timeout =2000;
            request.ReadWriteTimeout =2000;
            request.ContentType = contentType;
            request.ContentLength = (long)postForm.Length;

            try
            {
                using (Stream requestStream = request.GetRequestStream())
                {
                    int bufferSize = 4096;
                    int position = 0;
                    while (position < postForm.Length)
                    {
                        bufferSize = Math.Min(bufferSize, postForm.Length - position);

                        byte[] data = new byte[bufferSize];
                        Array.Copy(postForm, position, data, 0, bufferSize);
                        requestStream.Write(data, 0, data.Length);
                        position += data.Length;
                    }
                    //requestStream.Write(formData, 0, formData.Length);
                    requestStream.Close();
                }
            }
            catch (Exception ex)
            {
                return ex.Message;                
            }

            HttpWebResponse result;

            try
            {
                result = (HttpWebResponse)(request.GetResponse());
            }
            catch (Exception ex)
            {
                return ex.Message;
            }

            StreamReader streamReader = new StreamReader(result.GetResponseStream());
            return streamReader.ReadToEnd();
        }

        private static byte[] GetImageInfo(string path)//通过路径获取图片信息
        {
            Bitmap bmp = new Bitmap(path);
            byte[] imageInfo;

            using (Stream stream = new MemoryStream())
            {
                bmp.Save(stream,ImageFormat.Jpeg);
                byte[] arr = new byte[stream.Length];
                stream.Position = 0;
                stream.Read(arr, 0, (int)stream.Length);
                stream.Close();
                imageInfo = arr;
            }

            return imageInfo;
        }

    }

调用代码：

        static void Main(string[] args)
        {
            string imagePath = @"D:	estimage1.jpg";
            string url = "https://api-cn.faceplusplus.com/facepp/v3/detect";
            RequestForm.PostImage postImage = new RequestForm.PostImage(imagePath);

            Dictionary<string, object> postParameter = new Dictionary<string, object>();
            postParameter.Add("api_key", "*************************");
            postParameter.Add("api_secret", "**************************");
            postParameter.Add("image_file", postImage);
            //postParameter.Add("image_url", "http://imgtu.5011.net/uploads/content/20170328/7150651490664042.jpg");

            string result = RequestForm.OnRequest(postParameter, url);
            Console.WriteLine(result);
            Console.ReadKey();
        }

调用时参数为请求的url以及Dictionary<string, object> 类型的主体参数，传入图片时只需要一个参数调用时的key（上述代码为"image_file"）和包含图片路径的对象postImage，如果传入参数还需要其他文件如Txt格式等的文件时，只需要通过filestream读取出来即可