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German Hayles
Posts: 41
Joined: 2015-04-27
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Recently I found it necessary to add a Timer (System.Timers.Timer) object to my class OutlookItemEventsClass. It's derived from AddinExpress.MSO.ADXOutlookItemEvents.
Experience tells me that when dealing with unmanaged resources in a class it's usually best to implement the Dispose Design Pattern. Below is a code snippet of what I did. I was wondering if I'd missed anything, or if there were any "Gotchas"
public class OutlookItemEventsClass : AddinExpress.MSO.ADXOutlookItemEvents
{
static System.Timers.Timer _Timer = null; //UNMANAGED RESOURCE
public OutlookItemEventsClass(AddinExpress.MSO.ADXAddinModule module): base(module)
{
_Timer = new System.Timers.Timer(1000);
_Timer.Elapsed += new System.Timers.ElapsedEventHandler(WhatTheHey);
_Timer.AutoReset = false;
}
#region Dispose Design pattern
// Flag: has Dispose already been called?
bool _disposed = false;
// Public implementation of Dispose pattern callable by consumers.
public override void Dispose()
{
base.Dispose(); // CALLING BASE CLASS DISPOSE
Dispose(true);
GC.SuppressFinalize(this);
}
// Protected implementation of Dispose pattern.
protected virtual void Dispose(bool disposing)
{
if (_disposed)
return;
if (disposing)
{
// Managed code gets freed here
}
// Unmanaged code gets freed here
//
if (_Timer != null)
{
log.Debug("Disposing _Timer resource");
_Timer.Dispose();
_Timer = null;
}
_disposed = true;
}
/// <summary>
/// Finalizers are used in the case of a class containing unmanaged code
/// "_Timer" is unmanaged
/// </summary>
~OutlookItemEventsClass()
{
// Finalizer calls Dispose(false)
log.Info("Finalizer called for OutlookItemEventsClass");
Dispose(false);
}
#endregion
}
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Andrei Smolin
Add-in Express team
Posts: 18829
Joined: 2006-05-11
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Hello German,
Since it is mentioned in the System.Timers namespace, I assume this is a managed object, not unmanaged one.
In a COM add-in you should only use System.Windows.Forms.Timer because this timer fires its event on the main thread. You may run into many, many issues when using a timer that fires its event on a background thread *if* you use any Office object model on that thread. The point is: all Office object models are not thread safe.
Andrei Smolin
Add-in Express Team Leader |
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German Hayles
Posts: 41
Joined: 2015-04-27
|
Thanks!
I wasn't aware of System.Windows.Forms.Timer and the threading issue you brought up.
My only point of disagreement is about System.Timers. System.Timers.Timer has a call to "Dispose". I wouldn't think that Microsoft would provide a "Dispose" method on a managed object.
That said, I am going to follow your suggestion and switch over to System.Windows.Forms.Timer. I'd like to avoid any threading surprises as much as possible. |
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Andrei Smolin
Add-in Express team
Posts: 18829
Joined: 2006-05-11
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No problem.
Andrei Smolin
Add-in Express Team Leader |
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