C#中HttpWebRequest的用法

前言

HttpWebRequest是一个常用的类，用于发送和接收HTTP请求。在C#中使用HttpWebRequest可以实现各种功能，包括发送GET和POST请求、处理Cookie、设置请求头、添加参数等。本文将深入介绍HttpWebRequest的用法，并给出一些常见的示例。

1. 发送GET请求

使用HttpWebRequest发送GET请求非常简单，只需指定目标URL即可。以下是发送GET请求的示例代码：

using System;
using System.IO;
using System.Net;

class Program
{
    static void Main()
    {
        string url = "https://www.example.com/api/data";
        
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
        request.Method = "GET";
        
        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        
        using (StreamReader streamReader = new StreamReader(response.GetResponseStream()))
        {
            string responseData = streamReader.ReadToEnd();
            
            Console.WriteLine(responseData);
        }
    }
}

上述代码中，首先通过WebRequest.Create方法创建一个HttpWebRequest实例，并指定目标URL。然后设置请求方法为GET，通过GetResponse方法发送请求并获取响应。最后通过StreamReader对象读取响应数据。

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2. 发送POST请求

发送POST请求与发送GET请求类似，只需将请求方法设置为POST，并设置请求体的数据。以下是发送POST请求的示例代码：

using System;
using System.IO;
using System.Net;
using System.Text;

class Program
{
    static void Main()
    {
        string url = "https://www.example.com/api/data";
        string requestData = "param1=value1&param2=value2";

        byte[] byteData = Encoding.UTF8.GetBytes(requestData);

        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
        request.Method = "POST";
        request.ContentType = "application/x-www-form-urlencoded";
        request.ContentLength = byteData.Length;

        using (Stream requestStream = request.GetRequestStream())
        {
            requestStream.Write(byteData, 0, byteData.Length);
        }

        HttpWebResponse response = (HttpWebResponse)request.GetResponse();

        using (StreamReader streamReader = new StreamReader(response.GetResponseStream()))
        {
            string responseData = streamReader.ReadToEnd();

            Console.WriteLine(responseData);
        }
    }
}

上述代码中，首先将请求体的数据转换为字节数组，并设置请求方法为POST。然后设置Content-Type头为application/x-www-form-urlencoded，并设置请求体的长度。接着通过GetRequestStream方法获取请求流，并将请求数据写入请求流中。发送请求并获取响应的过程与发送GET请求相同。

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3. 设置请求头和处理Cookie

HttpWebRequest还提供了一些方法和属性来设置请求头和处理Cookie。以下是设置请求头和处理Cookie的示例代码：

using System;
using System.IO;
using System.Net;

class Program
{
    static void Main()
    {
        string url = "https://www.example.com/api/data";
        
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
        request.Method = "GET";
        
        // 设置请求头
        request.Headers["Authorization"] = "Bearer xxxxxxx";
        request.UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.45 Safari/537.36";
        
        // 处理Cookie
        request.CookieContainer = new CookieContainer();
        request.CookieContainer.Add(new Uri(url), new Cookie("cookie1", "value1"));
        
        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        
        using (StreamReader streamReader = new StreamReader(response.GetResponseStream()))
        {
            string responseData = streamReader.ReadToEnd();
            
            Console.WriteLine(responseData);
        }
    }
}

上述代码中，使用request.Headers属性可以设置请求头的键值对。通过设置UserAgent属性可以伪装请求的浏览器标识。通过创建CookieContainer对象并使用Add方法添加Cookie来处理Cookie。

4. 添加参数和处理响应

使用HttpWebRequest发送请求时，可能需要添加一些参数和在接收到响应后进行处理。以下是添加参数和处理响应的示例代码：

using System;
using System.IO;
using System.Net;
using System.Text;

class Program
{
    static void Main()
    {
        string url = "https://www.example.com/api/data";
        string requestData = "param1=value1&param2=value2";

        byte[] byteData = Encoding.UTF8.GetBytes(requestData);

        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
        request.Method = "POST";
        request.ContentType = "application/x-www-form-urlencoded";
        request.ContentLength = byteData.Length;

        using (Stream requestStream = request.GetRequestStream())
        {
            requestStream.Write(byteData, 0, byteData.Length);
        }

        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        
        // 处理响应
        HttpStatusCode statusCode = response.StatusCode;
        string statusDescription = response.StatusDescription;

        using (StreamReader streamReader = new StreamReader(response.GetResponseStream()))
        {
            string responseData = streamReader.ReadToEnd();

            Console.WriteLine(responseData);
        }
    }
}