C#通过API接口返回流式响应内容---SignalR方式

1、背景

在上两篇《C#通过API接口返回流式响应内容—分块编码方式》和《C#通过API接口返回流式响应内容—SSE方式》实现了流式响应的内容。
上面的这两个主要是通过HTTP的一些功能，除了这些之外，还有WebSocket的方式。C#中的WebSocket的有比较多的方案：SignalR、Fleck、FreeIM、WebSocket-Sharp、NetCoreServer等。其中SignalR是微软官网推荐的、Fleck是WebSocket的C#的开源项目，并且用的比较多，其他三个（FreeIM、WebSocket-Sharp、NetCoreServer）本人未使用，但原理相同，大家可以网上找找方案。
本篇主要是使用SignalR的方案

2、效果

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3、具体代码

3.1、创建一个Hub

在这里插入图片描述
创建一个Hub服务，本质上它是一个服务器，用作一个服务转发。它是通过继承Hub实现。

using Microsoft.AspNetCore.SignalR;namespace SignalRHub.Hubs
{public class DeepSeekChat:Hub{public async Task SendDeepSeekStream(string msg){await Clients.All.SendAsync("ReceiveMsg", msg); //非常简单的方法，就是直接推送数据}}
}

3.2、配置Hub

在program.cs中配置Hub

using Microsoft.AspNetCore.SignalR;using SignalRHub.Hubs;var builder = WebApplication.CreateBuilder(args);builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
builder.Services.AddSignalR();      //【添加SignalR服务】
var app = builder.Build();
// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{app.UseSwagger();app.UseSwaggerUI();
}//app.UseHttpsRedirection();
app.UseCors(MyAllowSpecificOrigins);app.UseAuthorization();app.MapControllers();
app.MapHub<DeepSeekChat>("/dschat"); //【配置Endpoint】
app.Run();

3.3、配置推送服务

当我们实现了DeepSeekChat时，我们如何通过服务器，将数据推送到终端呢？因此我们需对外的API接口，当我们调用API的接口时，API方法内部调用signalr的实例，并调用推送方法，从而将我们的内容推送到终端。
在apicontroller中或者program.cs
在apicontroller中的方法如下，【这个是一个Get方法】

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.SignalR;
using SignalRHub.Hubs;namespace SignalRHub.Controllers
{[Route("api/[controller]")][ApiController]public class ViaAPIController : ControllerBase{private readonly IHubContext<DeepSeekChat> chatHub;public ViaAPIController(IHubContext<DeepSeekChat> chatHub){this.chatHub = chatHub;}[HttpGet("sendmsg")]public async Task SendMsg(){//模拟deepseek的对话内容var phrases = new string[] { "你好！", "我是", "北京清华长庚医院", "信息管理部的", "郑林" };foreach (var item in phrases){await chatHub.Clients.All.SendAsync("ReceiveMsg", item);await Task.Delay(1000);}}}
}

在program.cs的代码如下：

//上文中的其他配置略过
app.UseAuthorization();
app.MapControllers();
app.MapHub<DeepSeekChat>("/dschat");
//【这儿就是直接配置的，两者的效果是一样的，都是发送数据】
app.MapPost("sendNotification", async (string msg, IHubContext<DeepSeekChat> context) => {var phrases = new string[] { "你好！", "我是", "北京清华长庚医院", "信息管理部的", "郑林" };foreach (var item in phrases){await context.Clients.All.SendAsync("ReceiveMsg", item);await Task.Delay(1000);}
});app.Run();

两者的效果是一致的

3.4、前端代码

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>SignalR Client</title><script src="https://cdnjs.cloudflare.com/ajax/libs/microsoft-signalr/3.1.18/signalr.min.js"></script>
</head>
<body><h3>流式响应</h3><div id="stockPrices"></div><script>const connection = new signalR.HubConnectionBuilder().withUrl("http://localhost:5071/dschat").build();connection.on("ReceiveMsg", (msg) => {const stockPricesDiv = document.getElementById("stockPrices");stockPricesDiv.innerHTML+= msg +'&nbsp;'; });connection.start().then(() => {console.log("SignalR connection started.");}).catch(err => {console.error("Error connecting to SignalR: ", err);});window.addEventListener("beforeunload", () => {connection.stop().then(() => {console.log("SignalR connection stopped.");}).catch(err => {console.error("Error stopping SignalR connection: ", err);});});</script>
</body>
</html>

比较简单

3.5、配置Cors

这样运行的话，浏览器是报错的，因为有Cors限制，因此需要在program.cs中配置

var MyAllowSpecificOrigins = "_myAllowSpecificOrigins";var builder = WebApplication.CreateBuilder(args);//设置CORS
builder.Services.AddCors(options => {options.AddPolicy(name: MyAllowSpecificOrigins,policy => {policy.SetIsOriginAllowed(t=>true) //默认全部访问.AllowAnyHeader().AllowAnyMethod().AllowCredentials();});
});
builder.Services.AddControllers();//其他配置//app.UseHttpsRedirection();
app.UseCors(MyAllowSpecificOrigins); //配置Cors
app.UseAuthorization();
app.MapControllers();

3.6、完整的program配置

完整的配置如下：

using Microsoft.AspNetCore.SignalR;
using SignalRHub.BackgroundServices;
using SignalRHub.Hubs;var MyAllowSpecificOrigins = "_myAllowSpecificOrigins";var builder = WebApplication.CreateBuilder(args);//设置CORS
builder.Services.AddCors(options => {options.AddPolicy(name: MyAllowSpecificOrigins,policy => {policy.SetIsOriginAllowed(t=>true) //.AllowAnyHeader().AllowAnyMethod().AllowCredentials();});
});builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
builder.Services.AddSignalR();//添加SignalR服务
//builder.Services.AddHostedService<Worker>(); //添加一个后台服务var app = builder.Build();// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{app.UseSwagger();app.UseSwaggerUI();
}//app.UseHttpsRedirection();
app.UseCors(MyAllowSpecificOrigins); //配置Corsapp.UseAuthorization();app.MapControllers();
app.MapHub<DeepSeekChat>("/dschat");app.MapPost("sendNotification", async (string msg, IHubContext<DeepSeekChat> context) => {var phrases = new string[] { "你好！", "我是", "北京清华长庚医院", "信息管理部的", "郑林" };foreach (var item in phrases){await context.Clients.All.SendAsync("ReceiveMsg", item);await Task.Delay(1000);}
});app.Run();