Observable.GroupBy < TSource、TKey、TElement > 方法 (IObservable < TSource > 、Func TSource、TKey > 、Func << TSource、TElement >)
將可觀察序列的專案分組，並使用指定的函式來選取產生的專案。
Namespace：System.Reactive.Linq
裝配： System.Reactive.dll) 中的 System.Reactive (
Syntax
'Declaration
<ExtensionAttribute> _
Public Shared Function GroupBy(Of TSource, TKey, TElement) ( _
source As IObservable(Of TSource), _
keySelector As Func(Of TSource, TKey), _
elementSelector As Func(Of TSource, TElement) _
) As IObservable(Of IGroupedObservable(Of TKey, TElement))
'Usage
Dim source As IObservable(Of TSource)
Dim keySelector As Func(Of TSource, TKey)
Dim elementSelector As Func(Of TSource, TElement)
Dim returnValue As IObservable(Of IGroupedObservable(Of TKey, TElement))
returnValue = source.GroupBy(keySelector, _
elementSelector)
public static IObservable<IGroupedObservable<TKey, TElement>> GroupBy<TSource, TKey, TElement>(
this IObservable<TSource> source,
Func<TSource, TKey> keySelector,
Func<TSource, TElement> elementSelector
)
[ExtensionAttribute]
public:
generic<typename TSource, typename TKey, typename TElement>
static IObservable<IGroupedObservable<TKey, TElement>^>^ GroupBy(
IObservable<TSource>^ source,
Func<TSource, TKey>^ keySelector,
Func<TSource, TElement>^ elementSelector
)
static member GroupBy :
source:IObservable<'TSource> *
keySelector:Func<'TSource, 'TKey> *
elementSelector:Func<'TSource, 'TElement> -> IObservable<IGroupedObservable<'TKey, 'TElement>>
JScript does not support generic types and methods.
類型參數
- TSource
類型來源。
- TKey
類型索引鍵。
- TElement
類型專案。
參數
- source
類型：System.IObservable< TSource>
可觀察的序列，其專案要分組。
- keySelector
類型：System.Func< TSource、TKey>
用來擷取各項目之索引鍵的函式。
- elementSelector
類型：System.Func< TSource、TElement>
函式，將每個來源專案對應至可觀察群組中的專案。
傳回值
類型：System.IObservable<IGroupedObservable< TKey、 TElement>>
可觀察群組序列，每個群組都會對應至唯一索引鍵值，其中包含共用相同索引鍵值的所有元素。
使用注意事項
在 Visual Basic 和 C# 中，您可以在IObservable< TSource > 類型的任何物件上呼叫這個方法作為實例方法。 使用執行個體方法語法呼叫這個方法時，請省略第一個參數。 如需詳細資訊，請參閱 或 。
備註
GroupBy 運算子可用來根據索引鍵值，將專案的來源序列分組成群組。 每個索引鍵值都是 keySelector 函式的結果，而且可以衍生自來源序列中的每個專案。 GroupBy 運算子的結果是由IGroupedObservable < TKey， TElement >序列所代表的群組專案序列。 IGroupedObservable 會公開可識別群組序列的索引鍵屬性。 結果群組序列中的實際專案是由套用至每個來源專案的 elementSelector 函式結果所控制。
範例
此範例程式碼會產生過去六小時內發生的事件記錄序列。 GroupBy 運算子接著會與 LINQ 語句搭配使用，根據評估為 「Error」 或 「Critical」 的 LevelDisplayName 屬性來分組事件記錄。 如果這是 true，則索引鍵選取器函式的結果為 true，導致事件記錄在錯誤群組中分組。 GroupBy 運算子的結果是 IGroupedObservable < Boolean EventRecord > 。 此 IGroupedObservable 序列已訂閱，以存取群組錯誤事件記錄檔專案。 程式碼會檢查群組的順序，以尋找索引鍵值為 true 的群組。 true 的索引鍵值會識別錯誤群組。 然後訂閱該錯誤群組，並將錯誤事件記錄檔專案寫入主控台視窗。
using System;
using System.Reactive.Linq;
using System.Reactive.Concurrency;
using System.Diagnostics.Eventing.Reader;
using System.IO;
namespace Example
{
class Program
{
static void Main()
{
//************************************************************************************************//
//*** Generate a sequence of event log entries that have been written to the system event log ***//
//*** within the last 6 hours. ***//
//************************************************************************************************//
const int eventLogTimeSpan = 6;
EventLogReader sysEventLog = new EventLogReader("System");
//****************************************************************************************************//
//*** Start with the last entry in the event log. ***//
//*** Stop on an event generated at a time more than the EventLogTimeSpan (6 hrs in this example). ***//
//*** Each iteration function will step back one entry. ***//
//*** The resultSelector function will just select each entry for inclusion in the sequence. ***//
//*** The ThreadPool schedule schedules the processing of the event log on a thread pool thread ***//
//****************************************************************************************************//
sysEventLog.Seek(SeekOrigin.End,0);
EventRecord lastEntry = sysEventLog.ReadEvent();
var eventLogEntrySeq = Observable.Generate(lastEntry,
x => (DateTime.Now - x.TimeCreated) < TimeSpan.FromHours(eventLogTimeSpan),
x => {sysEventLog.Seek(x.Bookmark,-1); return sysEventLog.ReadEvent();},
x => x,
Scheduler.ThreadPool);
//************************************************************************************************************//
//*** Use the GroupBy operator with LINQ to group the sequence into entries that are errors (key=true) and ***//
//*** those that are not errors (key=false). ***//
//************************************************************************************************************//
var eventLogGroupedSeq =
from entry in eventLogEntrySeq
group entry by (entry.LevelDisplayName == "Error") || (entry.LevelDisplayName == "Critical") into groupedEntries
select groupedEntries;
//***************************************************************************************//
//*** eventLogGroupedSeq is a IGroupedObservable<Boolean, EventRecord>. Subscribing ***//
//*** will return a sequence of the groups. For this example, we only want the group ***//
//*** where the key is true indicating the Error entries group. So we then subscribe ***//
//*** to that grouped sequence to write the error entries that occurred within the ***//
//*** last 6 hours. ***//
//***************************************************************************************//
eventLogGroupedSeq.Subscribe(groupedSeq =>
{
if (groupedSeq.Key == true)
{
groupedSeq.Subscribe(evtEntry => Console.WriteLine("ID : {0}\n" +
"Type : {1}\n" +
"Source: {2}\n" +
"Time Generated: {3}\n" +
"Message: {4}\n",
evtEntry.Id,
evtEntry.LevelDisplayName,
evtEntry.ProviderName,
evtEntry.TimeCreated.ToString(),
evtEntry.FormatDescription()));
}
});
Console.WriteLine("\nDisplaying error entries from the system event log\n" +
"that occurred within the last {0} hours...\n\n" +
"Press ENTER to exit...\n",eventLogTimeSpan);
Console.ReadLine();
}
}
}
下列輸出是使用範例程式碼所產生。
Displaying error entries from the system event log
that occurred within the last 6 hours...
Press ENTER to exit...
ID : 34001
Type : Error
Source: Microsoft-Windows-SharedAccess_NAT
Time Generated: 5/31/2011 4:39:18 AM
Message: The ICS_IPV6 failed to configure IPv6 stack.
ID : 34001
Type : Error
Source: Microsoft-Windows-SharedAccess_NAT
Time Generated: 5/31/2011 4:01:36 AM
Message: The ICS_IPV6 failed to configure IPv6 stack.
ID : 34001
Type : Error
Source: Microsoft-Windows-SharedAccess_NAT
Time Generated: 5/31/2011 3:49:29 AM
Message: The ICS_IPV6 failed to configure IPv6 stack.
ID : 34001
Type : Error
Source: Microsoft-Windows-SharedAccess_NAT
Time Generated: 5/31/2011 3:11:47 AM
Message: The ICS_IPV6 failed to configure IPv6 stack.
ID : 34001
Type : Error
Source: Microsoft-Windows-SharedAccess_NAT
Time Generated: 5/31/2011 2:59:40 AM
Message: The ICS_IPV6 failed to configure IPv6 stack.