C# 使用WebClient发送请求-马育民老师

# 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

```

# 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

原文出处：http://www.malaoshi.top/show_1IX6QS1ybygh.html