I have developed an Outlook VSTO addin. Some tasks should be made on a background thread. Typically, checking something in my local db or invoking a web request. After reading several posts, I dropped the idea of calling the Outlook Object Model (OOM) in a background thread.
I have some wpf controls and I successfully managed to use the .NET 40 TPL to perform the async task and when completed to "finish" the job (i.e. accessing the UI or the OOM) in the Main VSTA Thread.
To do so I use a syntax of the form:
Task<SomeResult> task = Task.Factory.StartNew(()=>{
//Do long tasks that have nothing to do with UI or OOM
return SomeResult();
});
//now I need to access the OOM
task.ContinueWith((Task<SomeResult> tsk) =>{
//Do something clever using SomeResult that uses the OOM
},TaskScheduler.FromCurrentSynchronizationContext());
So far so good. But now I want to do something similar when hooking an event in the OOM where there are no Form/WPF control. Precisely, my problem comes from the fact that TaskScheduler.FromCurrentSynchronizationContext() throws an exception.
For instance,
Items inboxItems = ...;
inboxItems.ItemAdd += AddNewInboxItems;
private void AddNewInboxItems(object item)
{
Task<SomeResult> task = Task.Factory.StartNew(()=>{
//Do long tasks that have nothing to do with OOM
return SomeResult()});
var scheduler = TaskScheduler.FromCurrentSynchronizationContext();
/* Ouch TaskScheduler.FromCurrentSynchronizationContext() throws an InvalidOperationException, 'The current SynchronizationContext may not be used as a TaskScheduler.' */
task.ContinueWith((Task<SomeResult> tsk) =>{
//Do something clever using SomeResult that uses the OOM
}),scheduler};
}
/* Ouch TaskScheduler.FromCurrentSynchronizationContext() throws an InvalidOperationException, 'The current SynchronizationContext may not be used as a TaskScheduler.' */
Note that I tried to create a TaskScheduler in addin initialization and putting it in a singleton as suggested here. But it does not work, the continuation task is not performed in the desired VSTA Main thread but another one (inspected with VisualStudio).
Any idea ?
