Can't connect from my Angular app to ASP.Net server SignalR

Question

I use ASP.Net framework to host the socket server. I created a Hub using SignalR, i ran it and then tried to connect to it from my angular app but recieved this error:

Failed to start the connection: TypeError: Cannot read properties of undefined (reading 'length')

There are no more details. I Enabled CORS with this code:

public void Configuration(IAppBuilder app)
        {
            app.UseCors(CorsOptions.AllowAll);
            app.MapSignalR("/Art", new HubConfiguration());
        }

and in the hub:

[EnableCors(origins: "http://localhost:4200", headers: "*", methods: "*")]
    public class ArtHub : Hub
    {
    ....
    }

I will highly appreciate any help

Answer 1

In configuration of your server use this to see detailed error info:

builder.Services.AddSignalR(o =>
{
    o.EnableDetailedErrors = true;
});

Use SignalR Hub endpoint like this:

app.UseEndpoints(endpoints =>
{
    endpoints.MapHub<ArtHub>("/art");
});