HttpClient获取数据

# 1、获取网页内容
```java
using System;
using System.Net.Http;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        using (var httpClient = new HttpClient())
        {
            string url = "https://www.163.com";
            string content = await httpClient.GetStringAsync(url);
            Console.WriteLine(content);
        }
    }
}
```
# 2、post 调用RESTful API
```java
class Program
{
    static async Task Main(string[] args)
    {
        using (var httpClient = new HttpClient())
        {
            var postData = new StringContent("{\"name\":\"John Doe\"}", Encoding.UTF8, "application/json");
            string url = "https://api.example.com/users";

HttpResponseMessage response = await httpClient.PostAsync(url, postData);
            if (response.IsSuccessStatusCode)
            {
                string content = await response.Content.ReadAsStringAsync();
                Console.WriteLine(content);
            }
        }
    }
}
```
# 3、上传文件
```java
using System;
using System.IO;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        using (var httpClient = new HttpClient())
        using (var multipartFormDataContent = new MultipartFormDataContent())
        {
            string filePath = @"path\to\your\file.txt";
            using (var fileStream = File.OpenRead(filePath))
            using (var fileContent = new StreamContent(fileStream))
            {
                fileContent.Headers.ContentType = MediaTypeHeaderValue.Parse("multipart/form-data");
                multipartFormDataContent.Add(fileContent, "file", Path.GetFileName(filePath));

string url = "https://api.example.com/upload";
                HttpResponseMessage response = await httpClient.PostAsync(url, multipartFormDataContent);

if (response.IsSuccessStatusCode)
                {
                    string content = await response.Content.ReadAsStringAsync();
                    Console.WriteLine(content);
                }
            }
        }
    }
}
```
# 4、处理JSON数据
```java
using System;
using System.Net.Http;
using System.Text;
using System.Text.Json;
using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        using (var httpClient = new HttpClient())
        {
            var user = new { Name = "John Doe", Email = "john@example.com" };
            string json = JsonSerializer.Serialize(user);
            var postData = new StringContent(json, Encoding.UTF8, "application/json");

string url = "https://api.example.com/users";
            HttpResponseMessage response = await httpClient.PostAsync(url, postData);

if (response.IsSuccessStatusCode)
            {
                string content = await response.Content.ReadAsStringAsync();
                var createdUser = JsonSerializer.Deserialize<dynamic>(content);
                Console.WriteLine($"User Created: {createdUser.Name}");
            }
        }
    }
}
```

# 5、获取Cookie
## 5.1 使用HttpClientHandler和CookieContainer
```java
var cookieContainer = new CookieContainer();
var handler = new HttpClientHandler() { CookieContainer = cookieContainer, UseCookies = true };
using (var client = new HttpClient(handler))
{
    // 发送请求，CookieContainer将自动捕获Set-Cookie头部  
    // ...  
    await client.GetAsync("https://www.baidu.com");
    // 之后，你可以通过CookieContainer访问这些Cookie  
    foreach (Cookie cookie in cookieContainer.GetCookies(new Uri("https://www.baidu.com")))
    {
        Console.WriteLine($"Cookie Name: {cookie.Name}, Value: {cookie.Value}");
    }
}
```
## 5.2 直接解析Set-Cookie头部
```java
using (var client = new HttpClient())
{
    var response = await client.GetAsync("https://www.baidu.com");

if (response.IsSuccessStatusCode && response.Headers.TryGetValues("Set-Cookie", out var cookieHeaders))
    {
        foreach (var cookieHeader in cookieHeaders)
        {
            Console.WriteLine(cookieHeader); // 直接打印Set-Cookie的值  
                                             // 这里可以添加逻辑来解析Cookie的详细信息  
        }
    }
}
```