關於C# winform怎么調用webapi來獲取到json數據

C/S系統也可以和B/S系統一樣實現“前后端分離”，那這樣寫winform就相當於純粹的前端頁面了，然后再單獨部署一個webapi項目，通過api調用數據庫進行數據的操作，有利於維護和數據安全性的提高，那么winform怎么去調用api接口呢，寫了一個demo，大家借鑒一下哈，本人才疏學淺，有不足和錯誤請指出：

        winform界面就不設計了，僅僅是為了測試是否調用到api，直接在創建的類庫中寫一個方法：

       /// <summary>
       /// 調用api返回json
       /// </summary>
       /// <param name="url">api地址</param>
       /// <param name="jsonstr">接收參數</param>
       /// <param name="type">類型</param>
       /// <returns></returns>
       public static string HttpApi(string url, string jsonstr, string type)
       {
           Encoding encoding = Encoding.UTF8;
           HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);//webrequest請求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界面的事件中調用該方法：

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

本地運行后變量str接收數據格式如下:

HttpWebRequest請求時無法發送具有此謂詞類型的內容正文。

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HttpWebRequest request = (HttpWebRequest)WebRequest.Create(postUrl); //--需要封裝的參數              request.CookieContainer = new CookieContainer();              CookieContainer cookie = request.CookieContainer; //如果用不到Cookie，刪去即可               //以下是發送的http頭              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頭看情況而定，但是下面倆必須加               request.ContentType = "application/x-www-form-urlencoded" ;              Encoding encoding = Encoding.UTF8; //根據網站的編碼自定義              request.Method = "get" ;  //--需要將get改為post才可行              string postDataStr;              Stream requestStream = request.GetRequestStream();              if (postDatas != "" )              {                  postDataStr=postDatas; //--需要封裝,形式如“arg=arg1&arg2=arg2”                  byte [] postData = encoding.GetBytes(postDataStr); //postDataStr即為發送的數據，                  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單數據的時候不能使用get方法，必須用post方法，

改為

1	request.Method = "post" ;  就可以了。  做一個記號

今天請求接口直接調了以前寫好的方法，結果報了（405）不支持方法的錯誤，一看是GET寫成POST了，改成GET之后，又報了無法發送具有此謂詞類型的內容正文錯誤的錯誤

原來之前的方法里面有GetRequestStream(), GET請求並不支持它。

把GetRequestStream()和相應的代碼注釋掉就OK了

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

特此記錄！

 

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