AggregateException Class

Definition

Namespace:

System

Assembly:

System.Runtime.dll

Source:

AggregateException.cs

Represents one or more errors that occur during application execution.

public ref class AggregateException : Exception

public class AggregateException : Exception

type AggregateException = class
    inherit Exception

Public Class AggregateException
Inherits Exception

Inheritance

Object

Exception

AggregateException

Examples

The following example catches the AggregateException exception and calls the Handle method to handle each exception it contains. Compiling and running the example with the first task1 variable should result in an AggregateException object that contains an UnauthorizedAccessException exception. Commenting out that line, uncommenting the second task1 variable, and compiling and running the example produces an AggregateException object that contains an IndexOutOfRangeException exception.

using System;
using System.IO;
using System.Threading.Tasks;

class Example
{
   static async Task Main(string[] args)
   {
      // Get a folder path whose directories should throw an UnauthorizedAccessException.
      string path = Directory.GetParent(
                              Environment.GetFolderPath(
                              Environment.SpecialFolder.UserProfile)).FullName;

      // Use this line to throw UnauthorizedAccessException, which we handle.
      Task<string[]> task1 = Task<string[]>.Factory.StartNew(() => GetAllFiles(path));

      // Use this line to throw an exception that is not handled.
      // Task task1 = Task.Factory.StartNew(() => { throw new IndexOutOfRangeException(); } );
      try
      {
          await task1;
      }
      catch (UnauthorizedAccessException)
      {
          Console.WriteLine("Caught unauthorized access exception-await behavior");
      }
      catch (AggregateException ae)
      {
          Console.WriteLine("Caught aggregate exception-Task.Wait behavior");
          ae.Handle((x) =>
          {
              if (x is UnauthorizedAccessException) // This we know how to handle.
              {
                  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 true;
              }
              return false; // Let anything else stop the application.
          });
      }

      Console.WriteLine("task1 Status: {0}{1}", task1.IsCompleted ? "Completed," : "",
                                                task1.Status);
   }

   static string[] GetAllFiles(string str)
   {
      // Should throw an UnauthorizedAccessException exception.
      return System.IO.Directory.GetFiles(str, "*.txt", System.IO.SearchOption.AllDirectories);
   }
}
// The example displays the following output if the file access task is run:
//       You do not have permission to access all folders in this path.
//       See your network administrator or try another path.
//       task1 Status: Completed,Faulted
// It displays the following output if the second task is run:
//       Unhandled Exception: System.AggregateException: One or more errors occurred. ---
//       > System.IndexOutOfRangeException: Index was outside the bounds of the array.
//          at Example.<Main>b__0()
//          at System.Threading.Tasks.Task.Execute()
//          --- End of inner exception stack trace ---
//          at System.AggregateException.Handle(Func`2 predicate)
//          at Example.Main(String[] args)

open System
open System.IO
open System.Threading.Tasks

let getAllFiles str =
    // Should throw an UnauthorizedAccessException exception.
    System.IO.Directory.GetFiles(str, "*.txt", System.IO.SearchOption.AllDirectories)

// Get a folder path whose directories should throw an UnauthorizedAccessException.
let path =
    let directory =
        Environment.SpecialFolder.UserProfile
        |> Environment.GetFolderPath
        |> Directory.GetParent
    directory.FullName

// Use this line to throw an exception that is not handled.
// let task1 = Task<string []>.Factory.StartNew(fun () -> raise (IndexOutOfRangeException()) )
let task1 = Task.Factory.StartNew(fun () -> getAllFiles (path))

let execute () =
    try
        task1.Wait()
    with
    | :? UnauthorizedAccessException -> printfn "Caught unauthorized access exception-await behavior"
    | :? AggregateException as ae ->
        printfn "Caught aggregate exception-Task.Wait behavior"

        ae.Handle (fun x ->
            match x with
            | :? UnauthorizedAccessException ->
                printfn "You do not have permission to access all folders in this path."
                printfn "See your network administrator or try another path."
                true
            | _ -> false)
    printfn $"""task1 Status: {if task1.IsCompleted then "Completed," else ""}{task1.Status}"""

execute ()

// The example displays the following output if the file access task is run:
//       You do not have permission to access all folders in this path.
//       See your network administrator or try another path.
//       task1 Status: Completed,Faulted
// It displays the following output if the second task is run:
//       Unhandled exception. System.AggregateException: One or more errors occurred. (Index was outside the bounds of the array.) (Index was outside the bounds of the array.)
//        ---> System.IndexOutOfRangeException: Index was outside the bounds of the array.
//          at Exception1.task1@19.Invoke()
//          at System.Threading.Tasks.Task`1.InnerInvoke()
//          at System.Threading.Tasks.Task.<>c.<.cctor>b__277_0(Object obj)
//          at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)   
//       --- End of stack trace from previous location ---
//          at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)   
//          at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
//          --- End of inner exception stack trace ---
//          at System.AggregateException.Handle(Func`2 predicate)
//          at <StartupCode$exception1>.$Exception1.main@()

Imports System.IO
Imports System.Threading.Tasks

Module Example
    Sub Main()
        ' Get a folder path whose directories should throw an UnauthorizedAccessException.
        Dim path As String = Directory.GetParent(
                                       Environment.GetFolderPath(
                                       Environment.SpecialFolder.UserProfile)).FullName

        ' Use this line to throw UnauthorizedAccessException, which we handle.
        Dim task1 = Task(Of String()).Factory.StartNew(Function() GetAllFiles(path))

        ' Use this line to throw an exception that is not handled.
        ' Task task1 = Task.Factory.StartNew(Sub() Throw New IndexOutOfRangeException() )
        Try
            task1.Wait()
        Catch ae As AggregateException
            ae.Handle(Function(x)
                          If TypeOf (x) Is UnauthorizedAccessException Then ' This we know how to handle
                              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 True
                          Else
                              Return False ' Let anything else stop the application.
                          End If
                      End Function)
        End Try

      Console.WriteLine("task1 Status: {0}{1}", If(task1.IsCompleted, "Completed,", ""), 
                                                task1.Status)
    End Sub

    Function GetAllFiles(ByVal str As String) As String()
        ' Should throw an UnauthorizedAccessException exception. 
        Return System.IO.Directory.GetFiles(str, "*.txt", System.IO.SearchOption.AllDirectories)
    End Function
End Module

Remarks

AggregateException is used to consolidate multiple failures into a single, throwable exception object. It is used extensively in the Task Parallel Library (TPL) and Parallel LINQ (PLINQ). For more information, see Exception Handling and How to: Handle Exceptions in a PLINQ Query. For additional information, see the Aggregating Exceptions entry in the .NET Matters blog.

Constructors

AggregateException()	Initializes a new instance of the AggregateException class with a system-supplied message that describes the error.
AggregateException(Exception[])	Initializes a new instance of the AggregateException class with references to the inner exceptions that are the cause of this exception.
AggregateException(IEnumerable<Exception>)	Initializes a new instance of the AggregateException class with references to the inner exceptions that are the cause of this exception.
AggregateException(SerializationInfo, StreamingContext)	Obsolete. Initializes a new instance of the AggregateException class with serialized data.
AggregateException(String)	Initializes a new instance of the AggregateException class with a specified message that describes the error.
AggregateException(String, Exception)	Initializes a new instance of the AggregateException class with a specified error message and a reference to the inner exception that is the cause of this exception.
AggregateException(String, Exception[])	Initializes a new instance of the AggregateException class with a specified error message and references to the inner exceptions that are the cause of this exception.
AggregateException(String, IEnumerable<Exception>)	Initializes a new instance of the AggregateException class with a specified error message and references to the inner exceptions that are the cause of this exception.

Properties

Data	Gets a collection of key/value pairs that provide additional user-defined information about the exception. (Inherited from Exception)
HelpLink	Gets or sets a link to the help file associated with this exception. (Inherited from Exception)
HResult	Gets or sets HRESULT, a coded numerical value that is assigned to a specific exception. (Inherited from Exception)
InnerException	Gets the Exception instance that caused the current exception. (Inherited from Exception)
InnerExceptions	Gets a read-only collection of the Exception instances that caused the current exception.
Message	Gets a message that describes the exception.
Source	Gets or sets the name of the application or the object that causes the error. (Inherited from Exception)
StackTrace	Gets a string representation of the immediate frames on the call stack. (Inherited from Exception)
TargetSite	Gets the method that throws the current exception. (Inherited from Exception)

Methods

Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
Flatten()	Flattens an AggregateException instances into a single, new instance.
GetBaseException()	Returns the Exception that is the root cause of this exception. This exception is either the root exception or the first AggregateException that contains either multiple inner exceptions or no inner exceptions at all.
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetObjectData(SerializationInfo, StreamingContext)	Obsolete. Initializes a new instance of the AggregateException class with serialized data.
GetType()	Gets the runtime type of the current instance. (Inherited from Exception)
Handle(Func<Exception,Boolean>)	Invokes a handler on each Exception contained by this AggregateException.
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Creates and returns a string representation of the current AggregateException.

Events

SerializeObjectState

Obsolete. Occurs when an exception is serialized to create an exception state object that contains serialized data about the exception. (Inherited from Exception)

Thread Safety

All public and protected members of AggregateException are thread-safe and may be used concurrently from multiple threads.