Observable.GroupBy<TSource、TKey、TElement> 方法 (IObservable<TSource>、Func<TSource、TKey>、Func<TSource、TElement>)

2011-06-28

对可观测序列的元素进行分组，并使用指定的函数选择生成的元素。

Namespace：System.Reactive.Linq
装配： System.Reactive.dll) 中的 System.Reactive (

语法

'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.

类型参数

TSource
类型源。

TKey
类型键。

TElement
类型元素。

参数

source
类型： System.IObservable<TSource>
要对其元素进行分组的可观察序列。

keySelector
类型： System.Func<TSource、TKey>
用于提取每个元素的键的函数。

elementSelector
类型： System.Func<TSource、TElement>
用于将每个源元素映射到可观测组中的元素的函数。

返回值

类型： System.IObservable<IGroupedObservable<TKey、TElement>>
一系列可观测组，其中每个组对应一个唯一键值，其中包含共享同一键值的所有元素。

使用说明

在 Visual Basic 和 C# 中，可以将此方法作为 IObservable<TSource> 类型的任何对象的实例方法调用。当使用实例方法语法调用此方法时，请省略第一个参数。有关详细信息，请参阅或。

备注

GroupBy 运算符用于根据键值将项的源序列分组到组中。每个键值都是 keySelector 函数的结果，可以派生自源序列中的每个项。 GroupBy 运算符的结果是由 IGroupedObservable<TKey， TElement> 序列表示的分组项序列。 IGroupedObservable 公开用于标识分组序列的键属性。生成的分组序列中的实际项由应用于每个源项的 elementSelector 函数的结果控制。

示例

此示例代码生成过去六小时内发生的事件日志记录序列。然后，GroupBy 运算符与 LINQ 语句一起使用，根据计算结果为“Error”或“Critical”的 LevelDisplayName 属性对错误事件记录进行分组。如果为 true，则键选择器函数的结果为 true，导致将事件记录分组到错误组中。 GroupBy 运算符的结果是 IGroupedObservable<布尔值 EventRecord>。此 IGroupedObservable 序列订阅以访问分组错误事件日志条目。代码检查组序列，以查找键值为 true 的组。 true 的键值标识错误组。然后订阅该错误组，并将错误事件日志条目写入控制台窗口。

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();
    }
  }
}

以下输出是使用示例代码生成的。

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.

另请参阅

参考

可观测类

GroupBy 重载

System.Reactive.Linq 命名空间

通过

Observable.GroupBy<TSource、TKey、TElement> 方法 (IObservable<TSource>、Func<TSource、TKey>、Func<TSource、TElement>)

语法

类型参数

参数

返回值

使用说明

备注

示例

另请参阅

参考

其他资源