服务端

builder.Services.AddSignalR();

app.UseEndpoints(endpoints =>
{
endpoints.MapRazorPages();
endpoints.MapHub<GraphGenerationHub>("/file");
});

public class GraphGenerationHub : Hub
{
public async Task SendMessage(string user, string message)
{
await Clients.All.SendAsync("ReceiveMessage", user, message);
}

}
注入
private readonly IHubContext<GraphGenerationHub> _hubContext;

public DemoController(SqlSugarClient _db,IHubContext<GraphGenerationHub> hubContext)
{
db = _db;
_hubContext = hubContext;
}
发消息
await _hubContext.Clients.All.SendAsync("ReceiveMessage", siz+"%");

前端
<script src="https://cdnjs.cloudflare.com/ajax/libs/microsoft-signalr/3.1.7/signalr.min.js"></script>
<script>
var messages = [];
// 创建 SignalR 连接
var connection = new signalR.HubConnectionBuilder()
.withUrl("http://localhost:8081/file")
.build();

    // 注册事件处理程序
    connection.on("messageReceived", function (message) {
        console.log(message);
    });

    // 启动连接
    connection.start()
        .then(function () {
            console.log("SignalR connection started.");
        })
        .catch(function (err) {
            console.error(err.toString());
        });

弄得比较简单 但是就是不通