这是我在经典模式下使用的内容.开销可以忽略不计.

/// <summary>
/// Class is called only on the first request
/// </summary>
private class AppStart
{
    static bool _init = false;
    private static Object _lock = new Object();
 
    /// <summary>
    /// Does nothing after first request
    /// </summary>
    /// <param name="context"></param>
    public static void Start(HttpContext context)
    {
        if (_init)
        {
            return;
        }
        //create class level lock in case multiple sessions start simultaneously
        lock (_lock)
        {
            if (!_init)
            {
                string server = context.Request.ServerVariables["SERVER_NAME"];
                string port = context.Request.ServerVariables["SERVER_PORT"];
                HttpRuntime.Cache.Insert("basePath","http://" + server + ":" + port + "/");
            }
        }
    }
}
 
protected void Session_Start(object sender,EventArgs e)
{
    //initializes Cache on first request
    AppStart.Start(HttpContext.Current);
}