Start of application

ASP.NET user id is not available in Application.Start, which allows writing to the database. (The website is running on a shared host, so I couldn't configure the permissions as I needed.) So, I implemented the following in global.asax. I am not sure if it is completely stream protected. I want to remove a delegate to eliminate blocking checking to optimize performance.

I wonder if "if (TheFirstReq! = Null)" can fail. Thanks to

delegate void FirstRequest();
static volatile FirstRequest TheFirstReq;
static object ObjLock = new Object();


void Application_Start(object sender, EventArgs e) 
{
    // Code that runs on application startup
    AppStartDateTime = DateTime.Now;
    TheFirstReq = FirstReq;
}

void FirstReq()
{
    lock (ObjLock)
    {
        if (TheFirstReq == null)
            return;
        TheFirstReq = null;
        // Log Application start.
    }
}

protected void Application_BeginRequest(object sender, EventArgs e)
{
    if (TheFirstReq != null)
        TheFirstReq();
}