Мы реализуем шаблон опроса в ASP.NET, который может применяться в вашем случае использования.
В нашем Global.ashx у нас есть:
protected void Application_Start(object sender, EventArgs e)
{
ConfigurationMonitor.Start();
}
, где ConfiguraitonMonitor выглядит примерно так:
public static class ConfigurationMonitor
{
private static readonly Timer timer = new Timer(PollingInterval);
public static bool MonitoringEnabled
{
get
{
return ((timer.Enabled || Working) ? true : false);
}
}
private static int _PollingInterval;
public static int PollingInterval
{
get
{
if (_PollingInterval == 0)
{
_PollingInterval = (Properties.Settings.Default.ConfigurationPollingIntervalMS > 0) ? Properties.Settings.Default.ConfigurationPollingIntervalMS : 5000;
}
return (_PollingInterval);
}
set { _PollingInterval = value; }
}
private static bool _Working = false;
public static bool Working
{
get { return (_Working); }
}
public static void Start()
{
Start(PollingInterval);
}
/// <summary>
/// Scans each DLL in a folder, building a list of the ConfigurationMonitor methods to call.
/// </summary>
private static List<ConfigurationMonitorAttribute> _MonitorMethods;
private static List<ConfigurationMonitorAttribute> MonitorMethods
{
get
{
if (_MonitorMethods == null)
{
_MonitorMethods = new List<ConfigurationMonitorAttribute>();
MonitorMethodsMessage = string.Empty;
foreach (var assemblyFile in Directory.GetFiles(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "bin"), Properties.Settings.Default.ConfigurtionMonitorDLLPath))
{
var assembly = Assembly.LoadFrom(assemblyFile);
foreach (ConfigurationMonitorAttribute monitor in assembly.GetCustomAttributes(typeof(ConfigurationMonitorAttribute), inherit: false))
{
_MonitorMethods.Add(monitor);
}
}
}
return (_MonitorMethods);
}
}
/// <summary>
/// Resets and instanciates MonitorMethods property to refresh dlls being monitored
/// </summary>
public static void LoadMonitoringMethods()
{
_MonitorMethods = null;
List<ConfigurationMonitorAttribute> monitorMethods = MonitorMethods;
}
/// <summary>
/// Initiates a timer to monitor for configuration changes.
/// This method is invoke on web application startup.
/// </summary>
/// <param name="pollingIntervalMS"></param>
public static void Start(int pollingIntervalMS)
{
if (Properties.Settings.Default.ConfigurationMonitoring)
{
if (!timer.Enabled)
{
LoadMonitoringMethods();
timer.Interval = pollingIntervalMS;
timer.Enabled = true;
timer.Elapsed += new ElapsedEventHandler(OnTimerElapsed);
timer.Start();
}
else
{
timer.Interval = pollingIntervalMS;
}
}
}
public static void Stop()
{
if (Properties.Settings.Default.ConfigurationMonitoring)
{
if (timer.Enabled)
{
timer.Stop();
}
}
}
/// <summary>
/// Monitors CE table for changes
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private static void OnTimerElapsed(object sender, ElapsedEventArgs e)
{
timer.Enabled = false;
PollForChanges();
timer.Enabled = true;
}
public static DateTime PollForChanges()
{
LastPoll = PollForChanges(LastPoll);
return (LastPoll);
}
public static DateTime PollForChanges(DateTime lastPollDate)
{
try
{
_Working = true;
foreach (ConfigurationMonitorAttribute monitor in MonitorMethods)
{
try
{
lastPollDate = monitor.InvokeMethod(lastPollDate);
if (lastPollDate > LastRefreshDate)
LastRefreshDate = lastPollDate;
}
catch (System.Exception ex)
{
// log the exception; my code omitted for brevity
}
}
}
catch (System.Exception ex)
{
// log the exception; my code omitted for brevity
}
finally
{
_Working = false;
}
return (lastPollDate);
}
#region Events
/// <summary>
/// Event raised when an AppDomain reset should occur
/// </summary>
public static event AppDomainChangeEvent AppDomainChanged;
public static void OnAppDomainChanged(string configFile, IDictionary<string, object> properties)
{
if (AppDomainChanged != null) AppDomainChanged(null, new AppDomainArgs(configFile, properties));
}
#endregion
}
Когда у нас есть сценарий использования, который хочетчтобы «участвовать» в этом механизме опроса, мы помечаем некоторый метод с атрибутом:
[assembly: ConfigurationMonitorAttribute(typeof(bar), "Monitor")]
namespace foo
{
public class bar
{
public static DateTime Monitor(DateTime lastPoll)
{
// do your expensive work here, setting values in your cache
}
}
}
Наш паттерн с методом, вызванным ConfigurationMonitor, возвращающим DateTime, был довольно странным краемдело.Вы, конечно, можете использовать метод void.
, где ConfigurationMonitorAttribute выглядит примерно так:
[AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
public class ConfigurationMonitorAttribute : Attribute
{
private Type _type;
private string _methodName;
public ConfigurationMonitorAttribute(Type type, string methodName)
{
_type = type;
_methodName = methodName;
}
public Type Type
{
get
{
return _type;
}
}
public string MethodName
{
get
{
return _methodName;
}
}
private MethodInfo _Method;
protected MethodInfo Method
{
get
{
if (_Method == null)
{
_Method = Type.GetMethod(MethodName, BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.Public);
if (_Method == null)
throw new ArgumentException(string.Format("The type {0} doesn't have a static method named {1}.", Type, MethodName));
}
return _Method;
}
}
public DateTime InvokeMethod(DateTime lastPoll)
{
try
{
return (DateTime)Method.Invoke(null, new object[] { lastPoll });
}
catch (System.Exception err)
{
new qbo.Exception.ThirdPartyException(string.Format("Attempting to monitor {0}/{1} raised an error.", _type, _methodName), err);
}
return lastPoll;
}
}