C#实现访问Web API Url提交数据并获取处理结果

应用场景

应用程序编程接口（Application Programming Interface，简称：API），是服务方定制开发一些预先定义的函数方法，并提供访问的方式及规则。访问 API 的开发人员无需理解其内部工作机制，只根据服务方提供的说明及规则，提交参数数据，并获取有需要的处理结果。

Web API  是 Web 服务器和 Web 浏览器之间的应用程序处理接口。我们常见的模式是访问 Web API Url 地址，POST 或 GET 所需要的参数数据，并获取 Json 、XML或其它指定格式的处理结果。 

范例运行环境

操作系统： Windows Server 2019 DataCenter

.net版本： .netFramework4.0 或以上

开发工具：VS2019  C# 

WebService 类

设计

WebService 类的 GetResponseResult 方法提供了访问 Web API Url 的能力，方法返回字符串（即API返回的处理结果），另外WebService 类还提供了 ErrorMessage 属性，通过访问此属性是否为空以判断方法是否正确返回了处理结果，GetResponseResult方法的 使用说明见如下表格：

实现

实现代码如下：

public sealed class WebService
{
 
 
        public string ErrorMessage = "";
 
        public string GetResponseResult(string url, System.Text.Encoding encoding, string method, string postData)
        {
            return GetResponseResult(url,encoding,method,postData,null);
        }
        public string GetResponseResult(string url, System.Text.Encoding encoding, string method, string postData,string[] headers,string ContentType= "application/x-www-form-urlencoded")
        {
            
            method = method.ToUpper();
            System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls | System.Net.SecurityProtocolType.Tls11 | System.Net.SecurityProtocolType.Tls12;
            if (method == "GET")
            {
                try
                {
                    WebRequest request2 = WebRequest.Create(@url);
                    request2.Method = method;
                    WebResponse response2 = request2.GetResponse();
                    Stream stream = response2.GetResponseStream();
                    StreamReader reader = new StreamReader(stream, encoding);
                    string content = reader.ReadToEnd();
                    return content;
                }
                catch (Exception ex)
                {
                    ErrorMessage = ex.Message;
                    return "";
                }
 
            }
            Stream outstream = null;
            Stream instream = null;
            StreamReader sr = null;
            HttpWebResponse response = null;
            HttpWebRequest request = null;
            byte[] data = encoding.GetBytes(postData);
            // 准备请求...
            try
            {
                // 设置参数
                request = WebRequest.Create(url) as HttpWebRequest;
                CookieContainer cookieContainer = new CookieContainer();
                request.CookieContainer = cookieContainer;
                request.AllowAutoRedirect = true;
                request.Method = method;
                request.Timeout = 1000000;
                if (headers != null)
                {
                    for(int i = 0; i < headers.GetLength(0); i++)
                    {
                        if (headers[i].Split(':').Length <2)
                        {
                            continue;
                        }
 
                        if (headers[i].Split(':').Length > 1) {
                            if (headers[i].Split(':')[0] == "Host") {
                                request.Host = headers[i].Split(':')[1];
                                continue;
                            }else if (headers[i].Split(':')[0] == "Content-Type")
                            {
                                request.ContentType = headers[i].Split(':')[1];
                                continue;
                            }
                        }
                        request.Headers.Add(headers[i]);
                    }
                }
                request.ContentType = ContentType;
                request.ContentLength = data.Length;
                outstream = request.GetRequestStream();
                outstream.Write(data, 0, data.Length);
                outstream.Close();
                //发送请求并获取相应回应数据
                response = request.GetResponse() as HttpWebResponse;
 
                instream = response.GetResponseStream();
                sr = new StreamReader(instream, encoding);
 
                string content = sr.ReadToEnd();
                sr.Close();
                sr.Dispose();
                
                return content;
            }
            catch (Exception ex)
            {
                ErrorMessage = ex.Message;
                return "";
            }
        }//get response result
}

调用

调用示例代码如下：

string content = "{\"key1\": 1,\"key2\": \"value2\"}";
string apiUrl = "https://api.t.com/test.aspx";
 
WebService ws = new WebService();
string resultStr = ws.GetResponseResult(settingUrl, Encoding.UTF8, "POST", content);
 
if(ErrorMessage!=""){
    Response.Write("访问没有成功，错误信息："+ErrorMessage);
}else{
    Response.Write(resultStr);
}

其它

我们在 WebService 类里创建了另一个实用方法：DownLoadFile，即提供对应的下载地址可以指定下载到本地文件，方法返回字符串（为空表示下载成功，不为空则显示错误信息）方法的使用说明见如下表格：

实现代码如下：

public string DownLoadFile(string url, string localfile)
{
            string pathUrl = url;
            System.Net.HttpWebRequest request = null;
            System.Net.HttpWebResponse response = null;
            //请求网络路径地址
            request = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(pathUrl);
            request.Timeout = 5000; // 超时时间
            //获得请求结果
            try
            {
                response = (System.Net.HttpWebResponse)request.GetResponse();
                Stream stream = response.GetResponseStream();
                //先创建文件
                Stream sos = new System.IO.FileStream(localfile, System.IO.FileMode.Create);
                byte[] img = new byte[1024];
                int total = stream.Read(img, 0, img.Length);
                while (total > 0)
                {
                    //之后再输出内容
                    sos.Write(img, 0, total);
                    total = stream.Read(img, 0, img.Length);
                }
                stream.Close();
                stream.Dispose();
                sos.Close();
                sos.Dispose();
                return "";
            }
            catch (Exception e)
            {
                return e.Message;
            }
}