C# Http调用详细代码_Asp.net

一、原理讲解

1. http调用的基本原理

http调用本质上是：

客户端（你的c#程序）向服务器通过网络发送http请求（如get、post等），
服务器接收请求并处理，
然后把响应（数据、状态码等）返回给客户端。

在c#中，最常用的http调用类库是 httpclient（.net framework 4.5+自带），它封装了底层的socket通信和http协议细节，使开发者可以更简单地发起网络请求。

2. 主要流程

建立连接：httpclient内部通过tcp协议与目标服务器建立连接（通常通过socket）。
发送请求：构造http请求报文（包括请求行、请求头、请求体）。
等待响应：服务器返回http响应报文（包括响应行、响应头、响应体）。
读取响应：httpclient读取响应内容，供程序处理。
关闭连接：连接可以复用（keep-alive），也可关闭。

3. 底层原理简述

httpclient基于httpwebrequest/httpwebresponse（.net core和.net 5+底层有优化）。
网络通信实际是通过socket进行数据收发。
http协议规定了请求和响应的格式，httpclient负责封装和解析。

4. 代码示例与报文结构

以get请求为例：

代码

using system;
using system.net.http;
using system.threading.tasks;
 
class program
{
    public static async task main(string[] args)
    {
        using (httpclient client = new httpclient())
        {
            httpresponsemessage response = await client.getasync("https://jsonplaceholder.typicode.com/posts/1");
            string content = await response.content.readasstringasync();
            console.writeline(content);
        }
    }
}

实际http报文

请求报文：

get /posts/1 http/1.1
host: jsonplaceholder.typicode.com
user-agent: ...
accept: ...
connection: keep-alive
...

响应报文：

http/1.1 200 ok
content-type: application/json; charset=utf-8
content-length: 292
...

{
  "userid": 1,
  "id": 1,
  "title": "...",
  "body": "..."
}

5. 关键点

请求方式：决定http请求的类型（get/post/put/delete等）。
请求头/响应头：包含元数据（如content-type、authorization等）。
请求体/响应体：实际传输的数据（如json、文本、文件等）。
状态码：服务器响应的处理结果（如200、404、500等）。

6. 总结

c#通过httpclient等类库，底层用socket实现http协议的数据收发。
httpclient负责封装http报文，简化开发流程。
http调用的本质是：构造请求 → 发送 → 等待响应 → 解析响应。

二、完整代码示例

1. 引入命名空间

using system;
using system.net.http;
using system.text;
using system.threading.tasks;

2. get请求

public static async task httpgetasync()
{
    using (httpclient client = new httpclient())
    {
        // 设置请求头（可选）
        client.defaultrequestheaders.add("user-agent", "c# app");
 
        // 发送get请求
        httpresponsemessage response = await client.getasync("https://jsonplaceholder.typicode.com/posts/1");
 
        // 判断是否成功
        if (response.issuccessstatuscode)
        {
            string content = await response.content.readasstringasync();
            console.writeline("get请求结果：");
            console.writeline(content);
        }
        else
        {
            console.writeline($"get请求失败，状态码：{response.statuscode}");
        }
    }
}

3. post请求（发送json）

public static async task httppostasync()
{
    using (httpclient client = new httpclient())
    {
        // 构造要发送的数据
        string json = "{\"title\": \"foo\", \"body\": \"bar\", \"userid\": 1}";
        stringcontent content = new stringcontent(json, encoding.utf8, "application/json");
 
        // 发送post请求
        httpresponsemessage response = await client.postasync("https://jsonplaceholder.typicode.com/posts", content);
 
        // 判断是否成功
        if (response.issuccessstatuscode)
        {
            string result = await response.content.readasstringasync();
            console.writeline("post请求结果：");
            console.writeline(result);
        }
        else
        {
            console.writeline($"post请求失败，状态码：{response.statuscode}");
        }
    }
}

4. 主函数调用示例

public static async task main(string[] args)
{
    await httpgetasync();
    await httppostasync();
}

5. 完整代码示例

using system;
using system.net.http;
using system.text;
using system.threading.tasks;
 
class program
{
    public static async task httpgetasync()
    {
        using (httpclient client = new httpclient())
        {
            client.defaultrequestheaders.add("user-agent", "c# app");
            httpresponsemessage response = await client.getasync("https://jsonplaceholder.typicode.com/posts/1");
            if (response.issuccessstatuscode)
            {
                string content = await response.content.readasstringasync();
                console.writeline("get请求结果：");
                console.writeline(content);
            }
            else
            {
                console.writeline($"get请求失败，状态码：{response.statuscode}");
            }
        }
    }
 
    public static async task httppostasync()
    {
        using (httpclient client = new httpclient())
        {
            string json = "{\"title\": \"foo\", \"body\": \"bar\", \"userid\": 1}";
            stringcontent content = new stringcontent(json, encoding.utf8, "application/json");
            httpresponsemessage response = await client.postasync("https://jsonplaceholder.typicode.com/posts", content);
            if (response.issuccessstatuscode)
            {
                string result = await response.content.readasstringasync();
                console.writeline("post请求结果：");
                console.writeline(result);
            }
            else
            {
                console.writeline($"post请求失败，状态码：{response.statuscode}");
            }
        }
    }
 
    public static async task main(string[] args)
    {
        await httpgetasync();
        await httppostasync();
    }
}

6. 添加自定义请求头（如token）

public static async task httpgetwithtokenasync()
{
    using (httpclient client = new httpclient())
    {
        // 添加bearer token
        client.defaultrequestheaders.authorization = new system.net.http.headers.authenticationheadervalue("bearer", "your_token_here");
        
        httpresponsemessage response = await client.getasync("https://api.example.com/data");
        string result = await response.content.readasstringasync();
        console.writeline(result);
    }
}

7. 发送表单数据（application/x-www-form-urlencoded）

public static async task httppostformasync()
{
    using (httpclient client = new httpclient())
    {
        var formdata = new formurlencodedcontent(new[]
        {
            new keyvaluepair<string, string>("username", "test"),
            new keyvaluepair<string, string>("password", "123456")
        });
 
        httpresponsemessage response = await client.postasync("https://httpbin.org/post", formdata);
        string result = await response.content.readasstringasync();
        console.writeline(result);
    }
}

8. 上传文件（multipart/form-data）

public static async task httppostfileasync()
{
    using (httpclient client = new httpclient())
    {
        using (var multipartformcontent = new multipartformdatacontent())
        {
            // 添加文件
            var filestream = system.io.file.openread("test.txt");
            multipartformcontent.add(new streamcontent(filestream), name: "file", filename: "test.txt");
 
            // 添加其他表单字段
            multipartformcontent.add(new stringcontent("value1"), "field1");
 
            httpresponsemessage response = await client.postasync("https://httpbin.org/post", multipartformcontent);
            string result = await response.content.readasstringasync();
            console.writeline(result);
        }
    }
}

9. 设置超时和异常处理

public static async task httpgetwithtimeoutasync()
{
    using (httpclient client = new httpclient())
    {
        client.timeout = timespan.fromseconds(5); // 设置超时时间
 
        try
        {
            httpresponsemessage response = await client.getasync("https://jsonplaceholder.typicode.com/posts/1");
            string content = await response.content.readasstringasync();
            console.writeline(content);
        }
        catch (taskcanceledexception ex)
        {
            console.writeline("请求超时: " + ex.message);
        }
        catch (exception ex)
        {
            console.writeline("请求异常: " + ex.message);
        }
    }
}

10. 反序列化json响应为对象

你可以使用 system.text.json 或 newtonsoft.json，这里用自带的 system.text.json。

using system.text.json;
 
public class post
{
    public int userid { get; set; }
    public int id { get; set; }
    public string title { get; set; }
    public string body { get; set; }
}
 
public static async task httpgetdeserializeasync()
{
    using (httpclient client = new httpclient())
    {
        httpresponsemessage response = await client.getasync("https://jsonplaceholder.typicode.com/posts/1");
        string content = await response.content.readasstringasync();
 
        // 反序列化为对象
        var post = jsonserializer.deserialize<post>(content);
        console.writeline($"标题: {post.title}, 内容: {post.body}");
    }
}

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