AggregateException.Handle(Func<Exception,Boolean>) Metodo
Definizione
Importante
Alcune informazioni sono relative alla release non definitiva del prodotto, che potrebbe subire modifiche significative prima della release definitiva. Microsoft non riconosce alcuna garanzia, espressa o implicita, in merito alle informazioni qui fornite.
Richiama un gestore in ogni Exception oggetto contenuto in questo AggregateExceptionoggetto .
public:
void Handle(Func<Exception ^, bool> ^ predicate);public void Handle(Func<Exception,bool> predicate);member this.Handle : Func<Exception, bool> -> unitPublic Sub Handle (predicate As Func(Of Exception, Boolean))Parametri
Predicato da eseguire per ogni eccezione. Il predicato accetta come argomento da Exception elaborare e restituisce un valore Boolean per indicare se l'eccezione è stata gestita.
Eccezioni
L'argomento predicate è Null.
Eccezione contenuta in questo AggregateException oggetto non gestita.
Esempio
In genere, un gestore eccezioni che intercetta un'eccezione AggregateException usa un ciclo foreach (in C#) o For Each (in Visual Basic) per gestire ogni eccezione nella raccolta InnerExceptions. L'esempio seguente usa invece il Handle metodo per gestire ogni eccezione e genera solo eccezioni che non CustomException sono istanze.
using System;
using System.Threading.Tasks;
public class Example
{
public static void Main()
{
var task1 = Task.Run( () => { throw new CustomException("This exception is expected!"); } );
try {
task1.Wait();
}
catch (AggregateException ae)
{
// Call the Handle method to handle the custom exception,
// otherwise rethrow the exception.
ae.Handle(ex => { if (ex is CustomException)
Console.WriteLine(ex.Message);
return ex is CustomException;
});
}
}
}
public class CustomException : Exception
{
public CustomException(String message) : base(message)
{}
}
// The example displays the following output:
// This exception is expected!
open System
open System.Threading.Tasks
type CustomException(message) =
inherit Exception(message)
let task1 =
Task.Run(fun () -> raise (CustomException "This exception is expected!"))
try
task1.Wait()
with
| :? AggregateException as ae ->
// Call the Handle method to handle the custom exception,
// otherwise rethrow the exception.
ae.Handle (fun ex ->
if ex :? CustomException then
printfn $"{ex.Message}"
ex :? CustomException)
// The example displays the following output:
// This exception is expected!
Imports System.Threading.Tasks
Module Example
Public Sub Main()
Dim task1 = Task.Run(Sub() Throw New CustomException("This exception is expected!"))
Try
task1.Wait()
Catch ae As AggregateException
' Call the Handle method to handle the custom exception,
' otherwise rethrow the exception.
ae.Handle(Function(e)
If TypeOf e Is CustomException Then
Console.WriteLine(e.Message)
End If
Return TypeOf e Is CustomException
End Function)
End Try
End Sub
End Module
Class CustomException : Inherits Exception
Public Sub New(s As String)
MyBase.New(s)
End Sub
End Class
' The example displays the following output:
' This exception is expected!
Di seguito è riportato un esempio più completo che usa il Handle metodo per fornire una gestione speciale per un oggetto durante l'enumerazione UnauthorizedAccessException dei file.
using System;
using System.IO;
using System.Threading.Tasks;
public class Example2
{
public static void Main()
{
// This should throw an UnauthorizedAccessException.
try {
var files = GetAllFiles(@"C:\");
if (files != null)
foreach (var file in files)
Console.WriteLine(file);
}
catch (AggregateException ae) {
foreach (var ex in ae.InnerExceptions)
Console.WriteLine("{0}: {1}", ex.GetType().Name, ex.Message);
}
Console.WriteLine();
// This should throw an ArgumentException.
try {
foreach (var s in GetAllFiles(""))
Console.WriteLine(s);
}
catch (AggregateException ae) {
foreach (var ex in ae.InnerExceptions)
Console.WriteLine("{0}: {1}", ex.GetType().Name, ex.Message);
}
}
static string[] GetAllFiles(string path)
{
var task1 = Task.Run( () => Directory.GetFiles(path, "*.txt",
SearchOption.AllDirectories));
try {
return task1.Result;
}
catch (AggregateException ae) {
ae.Handle( x => { // Handle an UnauthorizedAccessException
if (x is UnauthorizedAccessException) {
Console.WriteLine("You do not have permission to access all folders in this path.");
Console.WriteLine("See your network administrator or try another path.");
}
return x is UnauthorizedAccessException;
});
return Array.Empty<String>();
}
}
}
// The example displays the following output:
// You do not have permission to access all folders in this path.
// See your network administrator or try another path.
//
// ArgumentException: The path is not of a legal form.
open System
open System.IO
open System.Threading.Tasks
let getAllFiles path =
let task1 =
Task.Run(fun () -> Directory.GetFiles(path, "*.txt", SearchOption.AllDirectories))
try
task1.Result
with
| :? AggregateException as ae ->
ae.Handle (fun x ->
// Handle an UnauthorizedAccessException
if x :? UnauthorizedAccessException then
printfn "You do not have permission to access all folders in this path."
printfn "See your network administrator or try another path."
x :? UnauthorizedAccessException)
Array.empty
// This should throw an UnauthorizedAccessException.
try
let files = getAllFiles @"C:\"
if not (isNull files) then
for file in files do
printfn $"{file}"
with
| :? AggregateException as ae ->
for ex in ae.InnerExceptions do
printfn $"{ex.GetType().Name}: {ex.Message}"
printfn ""
// This should throw an ArgumentException.
try
for s in getAllFiles "" do
printfn $"{s}"
with
| :? AggregateException as ae ->
for ex in ae.InnerExceptions do
printfn $"{ex.GetType().Name}: {ex.Message}"
// The example displays the following output:
// You do not have permission to access all folders in this path.
// See your network administrator or try another path.
//
// ArgumentException: The path is empty. (Parameter 'path')
Imports System.IO
Imports System.Threading.Tasks
Module Example
Public Sub Main()
' This should throw an UnauthorizedAccessException.
Try
Dim files = GetAllFiles("C:\")
If files IsNot Nothing Then
For Each file In files
Console.WriteLine(file)
Next
End If
Catch ae As AggregateException
For Each ex In ae.InnerExceptions
Console.WriteLine("{0}: {1}", ex.GetType().Name, ex.Message)
Next
End Try
Console.WriteLine()
' This should throw an ArgumentException.
Try
For Each s In GetAllFiles("")
Console.WriteLine(s)
Next
Catch ae As AggregateException
For Each ex In ae.InnerExceptions
Console.WriteLine("{0}: {1}", ex.GetType().Name, ex.Message)
Next
End Try
Console.WriteLine()
End Sub
Function GetAllFiles(ByVal path As String) As String()
Dim task1 = Task.Run( Function()
Return Directory.GetFiles(path, "*.txt",
SearchOption.AllDirectories)
End Function)
Try
Return task1.Result
Catch ae As AggregateException
ae.Handle( Function(x)
' Handle an UnauthorizedAccessException
If TypeOf x Is UnauthorizedAccessException Then
Console.WriteLine("You do not have permission to access all folders in this path.")
Console.WriteLine("See your network administrator or try another path.")
End If
Return TypeOf x Is UnauthorizedAccessException
End Function)
End Try
Return Array.Empty(Of String)()
End Function
End Module
' The example displays the following output:
' You do not have permission to access all folders in this path.
' See your network administrator or try another path.
'
' ArgumentException: The path is not of a legal form.
Commenti
Ogni chiamata di predicate restituisce true o false per indicare se Exception è stato gestito. Dopo tutte le chiamate, tutte le eccezioni non gestite vengono inserite in un nuovo AggregateException che verrà generato. Se non sono presenti eccezioni non gestite, il Handle metodo restituisce semplicemente . Se una chiamata di genera un'eccezione predicate , interromperà l'elaborazione di altre eccezioni e propaga immediatamente l'eccezione generata as-is.