[英]How Can I Unfold This Event into an Observable Sequence?
好吧,就在我認為自己對事物有把握的時候,我又陷入了另一彎。
我正在嘗試創建一個可觀察的序列, 而不是這樣做:
((Outlook.MAPIFolderEvents_12_Event)calendarFolder).BeforeItemMove +=
Calendar_BeforeItemMove;
private void Calendar_BeforeItemMove(
object item,
Outlook.MAPIFolder destFolder,
ref bool cancel){ /*...*/ }
我正在嘗試使用Observable.FromEventPattern<TDelegate, TEventArgs> (Func<EventHandler<TEventArgs>, TDelegate>, Action<TDelegate>, Action<TDelegate>)
方法,但是由於所需的參數,我幾乎沒有遇到成功。 我最接近的是:
var itemBeforeMovedObservable = Observable
.FromEvent<Outlook.MAPIFolderEvents_12_BeforeItemMoveEventHandler, object>(handler =>
{
Outlook.MAPIFolderEvents_12_BeforeItemMoveEventHandler bimEventHandler =
(obj, f, ref cx) => // <-- Cannot resolve symbol 'cx'; Identifier expected
{
handler(obj); // <-- shouldn't this have the other parameters as well?
};
return bimEventHandler;
},
h => ((Outlook.MAPIFolderEvents_12_Event)calendarFolder).BeforeItemMove += h,
h => ((Outlook.MAPIFolderEvents_12_Event)calendarFolder).BeforeItemMove -= h);
在此先感謝您的指導。
我真的沒有辦法測試它,但是我想說,您最好將它包裝成一個運算符:
//Because that naming is ridiculous
using ItemMoveEventHandler = Outlook.MAPIFolderEvents_12_BeforeItemMoveEventHandler;
using ItemMoveEvent = Outlook.MAPIFolderEvents_12_Event;
//Used to wrap multiple arguments into a single object
public class MyMoveEventArgs {
public MyMoveEventArgs(Object item, MAPIFolder folder) {
this.Item = item;
this.Folder = folder;
}
public Object Item {get; private set;}
public MAPIFolder Folder {get; private set;}
}
//Create an extension method
public static IObservable<MyMoveEventArgs> BeforeMoveObservable(
this ItemMoveEvent folder,
Func<object, MAPIFolder, bool> shouldCancel) {
return Observable.FromEvent<ItemMoveEventHandler,
MoveEventArgs>
//Use the conversion overload
(emit => new ItemMoveEventHandler(
//The compiler seems to complain about cancel
//being implicit, so explicitly declare your params
(object item, MAPIFolder f, out bool cancel) =>
{
//cancel needs to be set somewhere in the body
if (!(cancel = shouldCancel(item, f)) {
emit(new MyMoveEventArgs(item, f));
}
}
},
h => folder.BeforeItemMove += h,
h => folder.BeforeItemMove -= h);
}
然后,您應該可以像這樣(未經測試)使用它:
calendarFolder.BeforeMoveObservable((obj, folder => /*Return if the event should be cancelled or not*/)
.Subscribe(x => /*Only reach here if the move was successful*/);
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