.Net HttpClient 使用 Cookie

在 HttpClient 中使用 Cookie

Cookie 是服务器存储在客户端的小型数据片段，可用于身份验证、会话跟踪等。

.Net HttpClient 支持 Cookie 功能，本教程详细介绍了Cookie 的管理与使用。

初始化

#!import "./Ini.ipynb"

什么是 Cookie

Cookie 是服务器发送到用户浏览器并存储在本地的一小段数据,用来进行会话管理（如登录状态）、个性化设置（如主题偏好）、跟踪用户行为等功能。

HttClient 手动管理 Cookie

如果只在简单的使用Cookie，想保持简洁、灵活。可以手管理。

发送带Cookie的请求

• 不使用Cookie

{   //不使用Cookie
    using (var client = new HttpClient(){BaseAddress=new Uri(webApiBaseUrl)})
    {
        var response = await client.GetAsync("/api/Cookie/GetRequestCookie"); 

        //确保请求成功
        response.EnsureSuccessStatusCode();

        //读取响应内容
        var content = await response.Content.ReadAsStringAsync();

        //输出 响应内容
        Console.WriteLine(content);
    }
}

• 手动设置Cookie: 在默认请求头中添加Cookie，适合快捷请求方法(Get,Post,Put,Delete等)

{   //多次请求时，都自动携带默认请求头Cookie

    var client = new HttpClient()
    {
        BaseAddress = new Uri(webApiBaseUrl),
    };

    //全局设置Cookie,所有快捷请求(Send方法的快捷方法：Get、Post、Put等)都会带上这个Cookie
    //快捷方法，不能单独设置Cookie; 只有Send方法才可以单独设置Cookie
    client.DefaultRequestHeaders.Add("Cookie", "Client=PolyglotNotebook,User=andy");

    //请求1
    var response = await client.GetAsync("/api/Cookie/GetRequestCookie"); 

    //确保请求成功
    response.EnsureSuccessStatusCode();

    //读取响应内容
    var content = await response.Content.ReadAsStringAsync();

    //输出 响应内容
    Console.WriteLine(content);

    //再次快捷请求，不用重新设置
    //请求2
    var response2 = await client.GetAsync("/api/Cookie/GetRequestCookie"); 

    //确保请求成功
    response2.EnsureSuccessStatusCode();

    //读取响应内容
    var content2 = await response2.Content.ReadAsStringAsync();

    //输出 响应内容
    Console.WriteLine(content2);

}

• 手动设置Cookie：每次请求设置 HttpRequestMessage，适合Send通用方法。当然可以合并默认请求头

{   //手动设置Cookie, 单次HttpRequestMessage合并默认请求头Cookie

    var client = new HttpClient()
    {
        BaseAddress = new Uri(webApiBaseUrl),
    };

    //全局设置Cookie,所有请求都会带上这个Cookie
    client.DefaultRequestHeaders.Add("Cookie", "Client=PolyglotNotebook,User=andy");

    //单请求设置
    var requestMessage = new HttpRequestMessage(HttpMethod.Get, "/api/Cookie/GetRequestCookie");
    
    //设置Cookie，会覆盖HttpClient设置的默认Cookie
    requestMessage.Headers.Add("Cookie", "Password=MyPassword,Role=Admin");
    //添加默认
    if(client.DefaultRequestHeaders.Contains("Cookie"))
    {
        requestMessage.Headers.Add("Cookie", client.DefaultRequestHeaders.GetValues("Cookie"));
    }

    var response = await client.SendAsync(requestMessage);
    var content = await response.Content.ReadAsStringAsync();
    Console.WriteLine(content);

    //响应头也会自动带上Cookie
    if(response.Headers.Contains("cookie"))
    {
        Console.Write($"响应头中Cookie为：");
        var cookies = response.Headers.GetValues("cookie");
        foreach (var cookie in cookies)
        {
            Console.WriteLine($"{cookie}");
        }
    }
    else
    {
        Console.WriteLine($"响应头中没有Cookie");
    }
}

查看响应头中的Cookie

{   //获取响应头中的Cookie

    var client = new HttpClient()
    {
        BaseAddress = new Uri(webApiBaseUrl),
    };

    var response = await client.GetAsync("/api/Cookie/GetResponseCookie");

    //获取响应头中的Cookie
    if(response.Headers.Contains("cookie"))
    {
        Console.Write($"响应头中Cookie为：");
        var cookies = response.Headers.GetValues("cookie");
        foreach (var cookie in cookies)
        {
            Console.WriteLine($"{cookie}");
        }
    }
    else
    {
        Console.WriteLine($"响应头中没有Cookie");
    }
}

HttClient 使用 CookieContainer 自动管理 Cookie

.NET 提供了 HttpClientHandler + CookieContainer 来自动管理 Cookie 生命周期和持久化。

使用 CookieContainer

{
    var handler = new HttpClientHandler()
    {
        UseCookies = true,
        CookieContainer = new CookieContainer(),
    };

    using var client = new HttpClient(handler)
    {
        BaseAddress = new Uri(webApiBaseUrl),
    };

    // 第一次请求，服务端设置 Cookie
    var response = await client.GetAsync("/api/Cookie/GetResponseCookie");
    response.EnsureSuccessStatusCode();

    // 第二次请求，自动携带之前设置的 Cookie
    var response2 = await client.GetAsync("/api/Cookie/GetRequestCookie");
    var content2 = await response2.Content.ReadAsStringAsync();
    Console.WriteLine(content2);
}

Cookie 持久化（保存与恢复）

若需要在程序重启后继续使用 Cookie，可将其序列化保存至文件或数据库。

• 保存 Cookie 到文件

///<summary
/// 保存Cookie到文件
///</summary>
public void SaveCookies(CookieContainer container, string filePath)
{
    using (var writer = new StreamWriter(filePath))
    {
        foreach (Cookie cookie in container.GetCookies(new Uri(webApiBaseUrl)))
        {
            writer.WriteLine($"{cookie.Name}={cookie.Value};Domain={cookie.Domain};Path={cookie.Path};Expires={cookie.Expires}");
        }
    }
}

//应用
{
    var handler = new HttpClientHandler()
    {
        UseCookies = true,
        CookieContainer = new CookieContainer(),
    };

    using (var client = new HttpClient(handler))
    {
        client.BaseAddress = new Uri(webApiBaseUrl);

        // 第一次请求，服务端设置 Cookie
        var response = await client.GetAsync("/api/Cookie/GetResponseCookie");
        response.EnsureSuccessStatusCode();

        SaveCookies(handler.CookieContainer, "cookies.txt");
    }
}

• 从文件中加载 Cookie

 <summary>
/// 从文件中加载 Cookie
/// </summary>
public CookieContainer LoadCookies(string filePath)
{
    var container = new CookieContainer();
    if (!File.Exists(filePath)) return container;

    foreach (var line in File.ReadAllLines(filePath))
    {
        var parts = line.Split(';');
        var nameValue = parts[0].Split('=');
        var cookie = new Cookie(nameValue[0], nameValue[1])
        {
            Domain = parts[1].Replace("Domain=", "").Trim(),
            Path = parts[2].Replace("Path=", "").Trim(),
            Expires = DateTime.Parse(parts[3].Replace("Expires=", "").Trim())
        };
        container.Add(cookie);
    }

    return container;
}

//发送请求：从文件中加载 Cookie, 在请求中携带
{
    var cookieBox = LoadCookies("cookies.txt");

    var handler = new HttpClientHandler()
    {
        UseCookies = true,
        CookieContainer = cookieBox,
    };

    var client = new HttpClient(handler)
    {
        BaseAddress = new Uri(webApiBaseUrl)
    };

    // 第一次请求，服务端设置 Cookie
    var response = await client.GetAsync("/api/Cookie/GetRequestCookie");
    response.EnsureSuccessStatusCode();

    var content = await response.Content.ReadAsStringAsync();

    Console.WriteLine(content);
}

跨域 Cookie 处理

默认情况下，CookieContainer 会根据域名自动隔离 Cookie。若需跨域共享 Cookie，可通过以下方式实现：

• 手动复制 Cookie

//示例代码，无实际请求
var sourceUri = new Uri("https://source.com");
var targetUri = new Uri("https://target.com");

foreach (Cookie cookie in handler.CookieContainer.GetCookies(sourceUri))
{
    var crossDomainCookie = new Cookie(cookie.Name, cookie.Value, cookie.Path, targetUri.Host);
    handler.CookieContainer.Add(targetUri, crossDomainCookie);
}

• 自定义 CookieContainer（高级）
  可以继承 CookieContainer 并重写相关方法以实现自定义 Cookie 共享策略。

进阶功能：Cookie 过期、安全标志、SameSite 设置等

• 设置 Cookie 高级属性

{
    //发送请求
    {
        var handler = new HttpClientHandler()
        {
            UseCookies = true,
            CookieContainer = new CookieContainer(),
        };

        var client = new HttpClient(handler)
        {
            BaseAddress = new Uri(webApiBaseUrl)
        };

        //设置Cookie
        var cookie = new Cookie("jwt_token", "a.b.c")
        {
            Expires = DateTime.Now.AddDays(7),
            Domain = new Uri(webApiBaseUrl).Host,
            Path = "/",
            Secure = true,           // 仅 HTTPS 传输
            HttpOnly = true,         // 防止 XSS 攻击
        };

        handler.CookieContainer.Add(new Uri(webApiBaseUrl), cookie);

        // 第一次请求，服务端设置 Cookie
        var response = await client.GetAsync("/api/Cookie/GetRequestCookie");
        response.EnsureSuccessStatusCode();

        var content = await response.Content.ReadAsStringAsync();

        Console.WriteLine(content);
    }
}

总结