When using SqlDependency without providing an options value, SqlDependency.Start() must be called prior to execution of a command added to the SqlDependency instance.

在调试SignalR程序时，提示一个异常：When using SqlDependency without providing an options value, SqlDependency.Start() must be called prior to execution of a command added to the SqlDependency instance.

解决方法是在Global.asax.cs文件中Application_Start()和Application_End()方法中添加下面高亮代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;
using Insus.NET.DataBases;
using System.Data.SqlClient;

namespace Insus.NET
{
    public class MvcApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();
            RouteConfig.RegisterRoutes(RouteTable.Routes);

            SqlDependency.Start(DB.ConnectionString);
        }

        protected void Application_End()
        {
            SqlDependency.Stop(DB.ConnectionString);
        }
    }
}