通过

Observable.FromAsyncPattern<T1、TResult> 方法 (Func<T1、AsyncCallback、Object、IAsyncResult>、Func<IAsyncResult、TResult>)

将 Begin/End 调用函数对转换为异步函数。

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

语法

'Declaration
Public Shared Function FromAsyncPattern(Of T1, TResult) ( _
    begin As Func(Of T1, AsyncCallback, Object, IAsyncResult), _
    end As Func(Of IAsyncResult, TResult) _
) As Func(Of T1, IObservable(Of TResult))

'Usage
Dim begin As Func(Of T1, AsyncCallback, Object, IAsyncResult)
Dim end As Func(Of IAsyncResult, TResult)
Dim returnValue As Func(Of T1, IObservable(Of TResult))

returnValue = Observable.FromAsyncPattern(begin, _
    end)

public static Func<T1, IObservable<TResult>> FromAsyncPattern<T1, TResult>(
    Func<T1, AsyncCallback, Object, IAsyncResult> begin,
    Func<IAsyncResult, TResult> end
)

public:
generic<typename T1, typename TResult>
static Func<T1, IObservable<TResult>^>^ FromAsyncPattern(
    Func<T1, AsyncCallback^, Object^, IAsyncResult^>^ begin, 
    Func<IAsyncResult^, TResult>^ end
)

static member FromAsyncPattern : 
        begin:Func<'T1, AsyncCallback, Object, IAsyncResult> * 
        end:Func<IAsyncResult, 'TResult> -> Func<'T1, IObservable<'TResult>> 

JScript does not support generic types and methods.

类型参数

  • T1
    第一种类型的函数。
  • TResult
    结果的类型。

参数

返回值

类型： System.Func<T1、 IObservable<TResult>>
开始/结束调用函数对。

备注

FromAsyncPattern 运算符用于简化异步调用。 它用一个处理异步调用的异步函数包装对开始/结束调用的异步调用。 函数返回与结果类型相同的可观察序列。 例如，可以设置对 System.IO.Directory.GetFiles 的异步调用。 该方法的结果是包含所请求文件列表的字符串数组。 因此，从 FromAsyncPattern 运算符返回的异步函数将返回 string[] 的可观测序列。 本主题的示例代码对此进行了演示。 此运算符有多种重载，用于处理采用不同数量输入参数的方法调用。 若要设置异步调用，请指定调用 FromAsyncPattern 运算符的类型。 指定的最终类型是返回值类型。 例如，System.IO.Directory.GetFiles 最多可以采用三个输入参数，并返回一个字符串数组作为结果。 以下代码片段显示了类型的顺序。

delegate string[] GetFilesDelegate(string searchPath, string searchPattern, SearchOption searchOption);


GetFilesDelegate getFiles = Directory.GetFiles;


//**************************************************************************************************//
//***  Observable.FromAsyncPattern<Param 1 Type, Param 2 Type, Param 3 Type, Return value type>  ***//
//**************************************************************************************************//
var getFileList = Observable.FromAsyncPattern<string, string, SearchOption, string[]>(getFiles.BeginInvoke, getFiles.EndInvoke);

示例

此示例演示如何异步调用 System.IO.Direcotry.GetFile 以枚举 C：\Program Files 目录下的所有文件。 该示例使用 FromAsyncPattern 运算符提供的异步函数。 操作事件处理程序充当异步调用的回调，以便将结果中的每个文件名写入控制台窗口。

using System;
using System.Reactive.Linq;
using System.IO;

namespace Example
{                                       
  delegate string[] GetFilesDelegate(string searchPath, string searchPattern, SearchOption searchOption);

  class Program
  {
    static void Main()
    {                                                                                                                    
      //********************************************************************************************************************//
      //*** For this example, Reactive Extensions is used to wrap an asynchronous call that recursively enumerates files ***//
      //*** in a given directory.                                                                                        ***//
      //********************************************************************************************************************//
      string mySearchPath = "C:\\Program Files";                                                                                   
      GetFilesDelegate getFiles = Directory.GetFiles;


      //*****************************************************************************************************************************//
      //*** Reactive Extensions will wrap the asynchronous call to the delegate returning the asynchronous function, getFileList. ***//
      //*** Calling the asynchronous function returns the observable sequence of the string[].                                    ***//
      //***                                                                                                                       ***//
      //*** There are many overloaded versions of the FromAsyncPattern operator. The types signified here are based on parameters ***//
      //*** in the signature of actual method being called asynchronously. The types are specified in their proper order followed ***//
      //*** by the return type (ex. <Param 1 type, Param 2 type, Param 3 type, return type> ).                                    ***//
      //*****************************************************************************************************************************//
      var getFileList = Observable.FromAsyncPattern<string, string, SearchOption, string[]>(getFiles.BeginInvoke, getFiles.EndInvoke);    
      IObservable<string[]> fileObservable = getFileList(mySearchPath,"*.*",SearchOption.AllDirectories);


      //*********************************************************************************************************************//
      //*** We subscribe to this sequence with an action event handler defined with the lambda expression. It acts as the ***//
      //*** callback for completion of the asynchronous operation.                                                        ***//
      //*********************************************************************************************************************//
      fileObservable.Subscribe(fileList =>
      {
        foreach (string f in fileList)
        {
          Console.WriteLine(f.ToString());
        }
      });


      Console.WriteLine("Running async enumeration of the {0} directory.\n\nPress ENTER to cancel...\n",mySearchPath);
      Console.ReadLine();
    }
  }
}

以下示例输出由示例代码生成。

Running async enumeration of the C:\Program Files directory.

Press ENTER to cancel...

C:\Program Files\desktop.ini
C:\Program Files\ATI\CIM\Bin64\atdcm64a.sys
C:\Program Files\ATI\CIM\Bin64\ATILog.dll
C:\Program Files\ATI\CIM\Bin64\ATIManifestDLMExt.dll
C:\Program Files\ATI\CIM\Bin64\ATISetup.exe
C:\Program Files\ATI\CIM\Bin64\CompressionDLMExt.dll
C:\Program Files\ATI\CIM\Bin64\CRCVerDLMExt.dll
C:\Program Files\ATI\CIM\Bin64\DetectionManager.dll
C:\Program Files\ATI\CIM\Bin64\difxapi.dll
C:\Program Files\ATI\CIM\Bin64\DLMCom.dll
C:\Program Files\ATI\CIM\Bin64\EncryptionDLMExt.dll
C:\Program Files\ATI\CIM\Bin64\InstallManager.dll
C:\Program Files\ATI\CIM\Bin64\InstallManagerApp.exe
C:\Program Files\ATI\CIM\Bin64\InstallManagerApp.exe.manifest
C:\Program Files\ATI\CIM\Bin64\LanguageMgr.dll
C:\Program Files\ATI\CIM\Bin64\mfc80u.dll
C:\Program Files\ATI\CIM\Bin64\Microsoft.VC80.ATL.manifest
C:\Program Files\ATI\CIM\Bin64\Microsoft.VC80.CRT.manifest
C:\Program Files\ATI\CIM\Bin64\Microsoft.VC80.MFC.manifest
C:\Program Files\ATI\CIM\Bin64\Microsoft.VC80.MFCLOC.manifest
C:\Program Files\ATI\CIM\Bin64\Microsoft.VC80.OpenMP.manifest
C:\Program Files\ATI\CIM\Bin64\msvcp80.dll
C:\Program Files\ATI\CIM\Bin64\msvcr80.dll
C:\Program Files\ATI\CIM\Bin64\PackageManager.dll
C:\Program Files\ATI\CIM\Bin64\readme.rtf
C:\Program Files\ATI\CIM\Bin64\SetACL64.exe

另请参阅

参考

可观测类

FromAsyncPattern 重载

System.Reactive.Linq 命名空间