Task.FromException Método

Definición

Sobrecargas

FromException(Exception)

Crea una Task que finalizó con una excepción especificada.Creates a Task that has completed with a specified exception.

FromException<TResult>(Exception)

Crea una Task<TResult> que finalizó con una excepción especificada.Creates a Task<TResult> that's completed with a specified exception.

FromException(Exception)

Crea una Task que finalizó con una excepción especificada.Creates a Task that has completed with a specified exception.

public:
 static System::Threading::Tasks::Task ^ FromException(Exception ^ exception);
public static System.Threading.Tasks.Task FromException (Exception exception);
static member FromException : Exception -> System.Threading.Tasks.Task

Parámetros

exception
Exception

Excepción con la que se finaliza la tarea.The exception with which to complete the task.

Devoluciones

Tarea con error.The faulted task.

Comentarios

Este método crea un objeto de Task cuya propiedad Status es Faulted y cuya propiedad Exception contiene exception.This method creates a Task object whose Status property is Faulted and whose Exception property contains exception. El método se utiliza normalmente cuando se sabe inmediatamente que el trabajo que realiza una tarea producirá una excepción antes de ejecutar una ruta de acceso de código más larga.The method is commonly used when you immediately know that the work that a task performs will throw an exception before executing a longer code path. Para obtener un ejemplo, vea la FromException<TResult>(Exception) sobrecarga.For an example, see the FromException<TResult>(Exception) overload.

FromException<TResult>(Exception)

Crea una Task<TResult> que finalizó con una excepción especificada.Creates a Task<TResult> that's completed with a specified exception.

public:
generic <typename TResult>
 static System::Threading::Tasks::Task<TResult> ^ FromException(Exception ^ exception);
public static System.Threading.Tasks.Task<TResult> FromException<TResult> (Exception exception);
static member FromException : Exception -> System.Threading.Tasks.Task<'Result>

Parámetros de tipo

TResult

Tipo de resultado devuelto por la tarea.The type of the result returned by the task.

Parámetros

exception
Exception

Excepción con la que se finaliza la tarea.The exception with which to complete the task.

Devoluciones

Tarea con error.The faulted task.

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. En lugar de ejecutar una ruta de acceso de código más larga que crea instancias de un objeto FileInfo y recupera el valor de su propiedad FileInfo.Length para cada archivo del directorio, el ejemplo simplemente llama al método FromException<TResult>(Exception) para crear una tarea con errores si un subdirectorio determinado no existe.Rather than executing a longer code path that instantiates a FileInfo object and retrieves the value of its FileInfo.Length property for each file in the directory, the example simply calls the FromException<TResult>(Exception) method to create a faulted task if a particular subdirectory does not exist.

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

Este método crea un objeto de Task<TResult> cuya propiedad Status es Faulted y cuya propiedad Exception contiene exception.This method creates a Task<TResult> object whose Status property is Faulted and whose Exception property contains exception. El método se utiliza normalmente cuando se sabe inmediatamente que el trabajo que realiza una tarea producirá una excepción antes de ejecutar una ruta de acceso de código más larga.The method is commonly used when you immediately know that the work that a task performs will throw an exception before executing a longer code path. En este ejemplo se ilustra.The example provides an illustration.

Se aplica a