Task<TResult>.Result Propiedad

Definición

Obtiene el valor de resultado de este objeto Task<TResult>.Gets the result value of this Task<TResult>.

public:
 property TResult Result { TResult get(); };
public TResult Result { get; }
member this.Result : 'Result
Public ReadOnly Property Result As TResult

Valor de propiedad

TResult

Valor de resultado de este Task<TResult>, que es del mismo tipo que el parámetro de tipo de la tarea.The result value of this Task<TResult>, which is of the same type as the task's type parameter.

Excepciones

Se canceló la tarea.The task was canceled. La colección InnerExceptions contiene un objeto TaskCanceledException .The InnerExceptions collection contains a TaskCanceledException object.

O bien,-or- Se inició una excepción durante la ejecución de la tarea.An exception was thrown during the execution of the task. La colección InnerExceptions contiene información sobre la excepción o excepciones.The InnerExceptions collection contains information about the exception or exceptions.

Ejemplos

El ejemplo siguiente es una utilidad de línea de comandos que calcula el número de bytes de los archivos de cada directorio cuyo nombre se pasa como argumento de la línea de comandos.The following example is a command-line utility that calculates the number of bytes in the files in each directory whose name is passed as a command-line argument. Si el directorio contiene archivos, ejecuta una expresión lambda que crea instancias de un objeto FileStream para cada archivo del directorio y recupera el valor de su propiedad FileStream.Length.If the directory contains files, it executes a lambda expression that instantiates a FileStream object for each file in the directory and retrieves the value of its FileStream.Length property. Si un directorio no contiene ningún archivo, simplemente llama al método FromResult para crear una tarea cuya propiedad Task<TResult>.Result es cero (0).If a directory contains no files, it simply calls the FromResult method to create a task whose Task<TResult>.Result property is zero (0). Cuando finalicen las tareas, el número total de bytes en todos los archivos del directorio está disponible en la propiedad Result.When the tasks finish, the total number of bytes in all a directory's files is available from the Result property.

using System;
using System.Collections.Generic;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      string[] args = Environment.GetCommandLineArgs();
      if (args.Length > 1) {
         List<Task<long>> tasks = new List<Task<long>>();
         for (int ctr = 1; ctr < args.Length; ctr++)
            tasks.Add(GetFileLengthsAsync(args[ctr]));

         try {
            Task.WaitAll(tasks.ToArray());
         }
         // Ignore exceptions here.
         catch (AggregateException) {}

         for (int ctr = 0 ; ctr < tasks.Count; ctr++) {
            if (tasks[ctr].Status == TaskStatus.Faulted)
               Console.WriteLine("{0} does not exist", args[ctr + 1]);
            else
               Console.WriteLine("{0:N0} bytes in files in '{1}'",
                                 tasks[ctr].Result, args[ctr + 1]);
         }
      }
      else {
         Console.WriteLine("Syntax error: Include one or more file paths.");
      }
   }

   private static Task<long> GetFileLengthsAsync(string filePath)
   {
      if (! Directory.Exists(filePath)) {
         return Task.FromException<long>(
                     new DirectoryNotFoundException("Invalid directory name."));
      }
      else {
         string[] files = Directory.GetFiles(filePath);
         if (files.Length == 0)
            return Task.FromResult(0L);
         else
            return Task.Run( () => { long total = 0;
                                     Parallel.ForEach(files, (fileName) => {
                                                 var fs = new FileStream(fileName, FileMode.Open,
                                                                         FileAccess.Read, FileShare.ReadWrite,
                                                                         256, true);
                                                 long length = fs.Length;
                                                 Interlocked.Add(ref total, length);
                                                 fs.Close(); } );
                                     return total;
                                   } );
      }
   }
}
// When launched with the following command line arguments:
//      subdir . newsubdir
// the example displays output like the following:
//       0 bytes in files in 'subdir'
//       2,059 bytes in files in '.'
//       newsubdir does not exist
Imports System.Collections.Generic
Imports System.IO
Imports System.Threading
Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      Dim args() As String = Environment.GetCommandLineArgs()
      If args.Length > 1 Then
         Dim tasks As New List(Of Task(Of Long))
         For ctr = 1 To args.Length - 1
            tasks.Add(GetFileLengthsAsync(args(ctr)))
         Next
         Try
            Task.WaitAll(tasks.ToArray())
         ' Ignore exceptions here.
         Catch e As AggregateException
         End Try

         For ctr As Integer = 0 To tasks.Count - 1
            If tasks(ctr).Status = TaskStatus.Faulted Then
               Console.WriteLine("{0} does not exist", args(ctr + 1))
            Else
               Console.WriteLine("{0:N0} bytes in files in '{1}'",
                                 tasks(ctr).Result, args(ctr + 1))
            End If
         Next
      Else
         Console.WriteLine("Syntax error: Include one or more file paths.")
      End If
   End Sub
   
   Private Function GetFileLengthsAsync(filePath As String) As Task(Of Long)
      If Not Directory.Exists(filePath) Then
         Return Task.FromException(Of Long)(
                     New DirectoryNotFoundException("Invalid directory name."))
      Else
         Dim files As String() = Directory.GetFiles(filePath)
         If files.Length = 0 Then
            Return Task.FromResult(0L)
         Else
            Return Task.Run( Function()
                                Dim total As Long = 0
                                Dim lockObj As New Object
                                Parallel.ForEach(files, Sub(fileName)
                                                           Dim fs As New FileStream(fileName, FileMode.Open,
                                                                     FileAccess.Read, FileShare.ReadWrite,
                                                                     256, True)
                                                           Dim length As Long = fs.Length
                                                           Interlocked.Add(total, length)
                                                           fs.Close()
                                                        End Sub)
                                Return total
                             End Function )
         End If
      End If
   End Function
End Module
' When launched with the following command line arguments:
'      subdir . newsubdir
' the example displays output like the following:
'       0 bytes in files in 'subdir'
'       2,059 bytes in files in '.'
'       newsubdir does not exist

Comentarios

El acceso al descriptor de acceso get de la propiedad bloquea el subproceso que realiza la llamada hasta que se completa la operación asincrónica. es equivalente a llamar al método Wait.Accessing the property's get accessor blocks the calling thread until the asynchronous operation is complete; it is equivalent to calling the Wait method.

Una vez que el resultado de una operación está disponible, se almacena y se devuelve inmediatamente en las llamadas subsiguientes a la propiedad Result.Once the result of an operation is available, it is stored and is returned immediately on subsequent calls to the Result property. Tenga en cuenta que, si se ha producido una excepción durante el funcionamiento de la tarea, o si la tarea se ha cancelado, la propiedad Result no devuelve un valor.Note that, if an exception occurred during the operation of the task, or if the task has been cancelled, the Result property does not return a value. En su lugar, si se intenta tener acceso al valor de propiedad, se produce una excepción AggregateException.Instead, attempting to access the property value throws an AggregateException exception.

Se aplica a

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