【SignalR】SignalR Invoke not working

Client 有連線上，但 Invoke 無反應，若 Wait() 則會出現 500 內部伺服器的錯誤等訊息。
Client is connected but Invoke doesn't seem to work.  Also 500 Internal Server Error show up when I use Wait() to check if the method done.

直接講結論，Server Hub 不能有非空的建構子，否則就會這樣(我猜可能會影響 Owin 架站的構築之類)。
Server Hub can't have none empty constructor, otherwise this would happen. Example below

public class SignalRServer : Hub
{
    ...
 
    // X
    public SignalRServer(string url)
    {
        string x = url;
    }
 
    // X
    public SignalRServer()
    {
        string x = "x";
    }
 
    // O
    public SignalRServer()
    {
    }
    
    // No ctor is OK as well
    
}