C# 使用WebClient发送请求

作者：马育民 • • 阅读：10118

发get请求

返回html字符串

WebClient client = new WebClient();
// 指定字符集
client.Encoding = System.Text.Encoding.UTF8;
// 必须携带下面数据，否则发送请求，报错：服务器500
client.Headers["User-Agent"] = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.0.0 Safari/537.36 Edg/117.0.2045.60";
client.Headers["Referer"] = url;

// 获取响应字符串
string html = client.DownloadString(url);

// 获取响应头
//WebHeaderCollection resp = client.ResponseHeaders;
//string te = resp.Get("Transfer-Encoding");
//string ct = resp.Get("Content-Type");
//string ce = resp.Get("Content-Encoding");
//string html = Encoding.UTF8.GetString(data);

返回字节数组

返回字节数组，然后进行解码

WebClient client = new WebClient();
// 必须携带下面数据，否则发送请求，报错：服务器500
client.Headers["User-Agent"] = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.0.0 Safari/537.36 Edg/117.0.2045.60";
client.Headers["Referer"] = url;

byte[] data = client.DownloadData(url);
string html = Encoding.UTF8.GetString(data);

携带请求头

每次发请求，都需要携带请求头。如果只携带一次请求头，那么发请求后，就会清空请求头

WebClient client = new WebClient();
// 指定字符集
client.Encoding = System.Text.Encoding.UTF8;
// 必须携带下面数据，否则发送请求，报错：服务器500
client.Headers["User-Agent"] = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.0.0 Safari/537.36 Edg/117.0.2045.60";
client.Headers["Referer"] = url;

// 获取响应字符串
string html = client.DownloadString(url);

下载文件

WebClient client = new WebClient();
// 指定字符集
client.Encoding = System.Text.Encoding.UTF8;
// 必须携带下面数据，否则发送请求，报错：服务器500
client.Headers["User-Agent"] = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.0.0 Safari/537.36 Edg/117.0.2045.60";
client.Headers["Referer"] = url;
// 下载文件，需指定下载的文件名
client.DownloadFile(downloadUrl, "a.zip");

解压缩gzip

如果web服务器返回的数据经过 gzip 压缩，就需要 继承 WebClient 类，并覆盖 GetWebRequest() 方法，才能解压缩

定义子类

internal class GZipWebClient : WebClient
{
    protected override WebRequest GetWebRequest(Uri address)
    {

        HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(address);
        request.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
        return request;
    }
}

调用

然后使用 GZipWebClient 发请求

GZipWebClient client = new GZipWebClient();
client.Encoding = System.Text.Encoding.UTF8;//定义语言
// 必须携带下面数据，否则发送请求，报错：服务器500
client.Headers["User-Agent"] = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.0.0 Safari/537.36 Edg/117.0.2045.60";
client.Headers["Referer"] = url;
//client.Headers["Accept-Encoding"] = "gzip, deflate, br";

string html = client.DownloadString(url);

参考：
https://blog.csdn.net/weixin_42301080/article/details/118394491

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