关于C# winform怎么调用webapi来获取到json数据

C/S系统也可以和B/S系统一样实现“前后端分离”，那这样写winform就相当于纯粹的前端页面了，然后再单独部署一个webapi项目，通过api调用数据库进行数据的操作，有利于维护和数据安全性的提高，那么winform怎么去调用api接口呢，写了一个demo，大家借鉴一下哈，本人才疏学浅，有不足和错误请指出：

        winform界面就不设计了，仅仅是为了测试是否调用到api，直接在创建的类库中写一个方法：

       /// <summary>
       /// 调用api返回json
       /// </summary>
       /// <param name="url">api地址</param>
       /// <param name="jsonstr">接收参数</param>
       /// <param name="type">类型</param>
       /// <returns></returns>
       public static string HttpApi(string url, string jsonstr, string type)
       {
           Encoding encoding = Encoding.UTF8;
           HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);//webrequest请求api地址
           request.Accept = "text/html,application/xhtml+xml,*/*";
           request.ContentType = "application/json";
           request.Method = type.ToUpper().ToString();//get或者post
           byte[] buffer = encoding.GetBytes(jsonstr);
           request.ContentLength = buffer.Length;
           request.GetRequestStream().Write(buffer, 0, buffer.Length);
           HttpWebResponse response = (HttpWebResponse)request.GetResponse();
           using (StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8))
           {
               return reader.ReadToEnd();
           }
       }

然后再winform界面的事件中调用该方法：

private void button3_Click(object sender, EventArgs e)
        {
            string url = "...(此处为api端口)/api/VisitorInfo/GetEndVisitorInfoList";
            var str = ApiHelper.HttpApi(url, "{}", "get");
        }

本地运行后变量str接收数据格式如下:

HttpWebRequest请求时无法发送具有此谓词类型的内容正文。

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HttpWebRequest request = (HttpWebRequest)WebRequest.Create(postUrl); //--需要封装的参数             request.CookieContainer = new CookieContainer();             CookieContainer cookie = request.CookieContainer;//如果用不到Cookie，删去即可              //以下是发送的http头             request.Referer = "";             request.Accept = "Accept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";             request.Headers["Accept-Language"] = "zh-CN,zh;q=0.";             request.Headers["Accept-Charset"] = "GBK,utf-8;q=0.7,*;q=0.3";             request.UserAgent = "User-Agent:Mozilla/5.0 (Windows NT 5.1) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/14.0.835.202 Safari/535.1";             request.KeepAlive = true;             //上面的http头看情况而定，但是下面俩必须加              request.ContentType = "application/x-www-form-urlencoded";             Encoding encoding = Encoding.UTF8;//根据网站的编码自定义             request.Method ="get";  //--需要将get改为post才可行             string postDataStr;             Stream requestStream = request.GetRequestStream();             if (postDatas != "")             {                 postDataStr=postDatas;//--需要封装,形式如“arg=arg1&arg2=arg2”                 byte[] postData = encoding.GetBytes(postDataStr);//postDataStr即为发送的数据，                 request.ContentLength = postData.Length;                 requestStream.Write(postData, 0, postData.Length);             }               HttpWebResponse response = (HttpWebResponse)request.GetResponse();             Stream responseStream = response.GetResponseStream();                 StreamReader streamReader = new StreamReader(responseStream, encoding);             string retString = streamReader.ReadToEnd();               streamReader.Close();             responseStream.Close();             return retString;

　　如果是以流的方式提交表单数据的时候不能使用get方法，必须用post方法，

改为

1	request.Method ="post";  就可以了。  做一个记号

今天请求接口直接调了以前写好的方法，结果报了（405）不支持方法的错误，一看是GET写成POST了，改成GET之后，又报了无法发送具有此谓词类型的内容正文错误的错误

原来之前的方法里面有GetRequestStream(), GET请求并不支持它。

把GetRequestStream()和相应的代码注释掉就OK了

      // Stream outStream = myRequest.GetRequestStream();
      // outStream.Write(arrB, 0, arrB.Length);
      //outStream.Close();

特此记录！

出处：https://blog.csdn.net/Andrewniu/article/details/79752653