dotnet · BillWagner · Nov 19, 2021 · Nov 19, 2021 · Nov 19, 2021 · Nov 19, 2021
@@ -0,0 +1,58 @@
+// <Snippet1>
+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 $"""task1 Status: {if task1.IsCompleted then "Completed," else ""}{task1.Status}"""
+
+execute ()
+
+// The example displays the following output if the file access task is run:
+//       You do not have permission to access all folders in this path.
+//       See your network administrator or try another path.
+//       task1 Status: Completed,Faulted
+// It displays the following output if the second task is run:
+//       Unhandled exception. System.AggregateException: One or more errors occurred. (Index was outside the bounds of the array.) (Index was outside the bounds of the array.)
+//        ---> System.IndexOutOfRangeException: Index was outside the bounds of the array.
+//          at [email protected]()
+//          at System.Threading.Tasks.Task`1.InnerInvoke()
+//          at System.Threading.Tasks.Task.<>c.<.cctor>b__277_0(Object obj)
+//          at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)   
+//       --- End of stack trace from previous location ---
+//          at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)   
+//          at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
+//          --- End of inner exception stack trace ---
+//          at System.AggregateException.Handle(Func`2 predicate)
+//          at <StartupCode$exception1>.$Exception1.main@()
+// </Snippet1>
@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net5.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="exception1.fs" />
+  </ItemGroup>
+
+</Project>
@@ -0,0 +1,38 @@
+module flatten2
+// <Snippet22>
+open System
+open System.Threading.Tasks
+
+type CustomException(message) =
+    inherit Exception(message)
+
+let task1 =
+    Task.Factory.StartNew (fun () ->
+        let child1 =
+            Task.Factory.StartNew(
+                (fun () ->
+                    let child2 =
+                        Task.Factory.StartNew(
+                            (fun () -> raise (CustomException "Attached child2 faulted,")),
+                            TaskCreationOptions.AttachedToParent
+                        )
+                    raise (CustomException "Attached child1 faulted.")),
+                TaskCreationOptions.AttachedToParent
+            )
+        ()
+    )
+
+try
+    task1.Wait()
+with
+| :? AggregateException as ae ->
+    for e in ae.Flatten().InnerExceptions do
+        if e :? CustomException then
+            printfn "%s" e.Message
+        else
+            reraise()
+
+// The example displays the following output:
+//    Attached child1 faulted.
+//    Attached child2 faulted.
+// </Snippet22>
@@ -0,0 +1,26 @@
+module handlemethod2
+// <Snippet16>
+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!
+// </Snippet16>
@@ -0,0 +1,53 @@
+module taskexceptions
+// <snippet12>
+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')
+// </snippet12>
@@ -0,0 +1,43 @@
+module taskexceptions2
+// <snippet13>
+open System
+open System.IO
+open System.Threading.Tasks
+
+let executeTasks () =
+    // Assume this is a user-entered String.
+    let path = @"C:\"
+
+    let tasks =
+        [| Task.Run (fun () ->
+               // This should throw an UnauthorizedAccessException.
+               Directory.GetFiles(path, "*.txt", SearchOption.AllDirectories))
+           :> Task
+           Task.Run (fun () ->
+               if path = @"C:\" then
+                   raise (ArgumentException "The system root is not a valid path.")
+
+               [| ".txt"; ".dll"; ".exe"; ".bin"; ".dat" |])
+           :> Task
+           Task.Run(fun () -> raise (NotImplementedException "This operation has not been implemented")) |]
+
+    try
+        Task.WaitAll(tasks)
+    with
+    | :? AggregateException as ae -> raise (ae.Flatten())
+
+try
+    executeTasks ()
+with 
+| :? AggregateException as ae ->
+    for e in ae.InnerExceptions do
+        printfn $"{e.GetType().Name}:\n   {e.Message}"
+
+// The example displays the following output:
+//       UnauthorizedAccessException:
+//          Access to the path 'C:\Documents and Settings' is denied.
+//       ArgumentException:
+//          The system root is not a valid path.
+//       NotImplementedException:
+//          This operation has not been implemented.
+// </Snippet13>
@@ -0,0 +1,15 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net5.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="flatten2.fs" />
+    <Compile Include="taskexceptions2.fs" />
+    <Compile Include="handlemethod2.fs" />
+    <Compile Include="taskexceptions.fs" />
+  </ItemGroup>
+
+</Project>
@@ -71,6 +71,7 @@
  The following example catches the <xref:System.AggregateException> exception and calls the <xref:System.AggregateException.Handle%2A> method to handle each exception it contains. Compiling and running the example with the first `task1` variable should result in an <xref:System.AggregateException> object that contains an <xref:System.UnauthorizedAccessException> exception. Commenting out that line, uncommenting the second `task1` variable, and compiling and running the example produces an <xref:System.AggregateException> object that contains an <xref:System.IndexOutOfRangeException> exception.  
 
  :::code language="csharp" source="~/samples/snippets/csharp/VS_Snippets_CLR_System/system.aggregateexception.class/cs/exception1.cs" id="Snippet1":::
+ :::code language="fsharp" source="~/samples/snippets/fsharp/VS_Snippets_CLR_System/system.aggregateexception.class/fs/exception1.fs" id="Snippet1":::
  :::code language="vb" source="~/samples/snippets/visualbasic/VS_Snippets_CLR_System/system.aggregateexception.class/vb/exception1.vb" id="Snippet1":::  
 
  ]]></format>
@@ -548,11 +549,13 @@
  In the following example, nested <xref:System.AggregateException> instances are flattened and handled in just one loop.  
 
  :::code language="csharp" source="~/samples/snippets/csharp/VS_Snippets_Misc/tpl_exceptions/cs/flatten2.cs" id="Snippet22":::
+ :::code language="fsharp" source="~/samples/snippets/fsharp/VS_Snippets_Misc/tpl_exceptions/fs/flatten2.fs" id="Snippet22":::
  :::code language="vb" source="~/samples/snippets/visualbasic/VS_Snippets_Misc/tpl_exceptions/vb/flatten2.vb" id="Snippet22":::  
 
  You can also use the <xref:System.AggregateException.Flatten%2A?displayProperty=nameWithType> method to rethrow the inner exceptions from multiple <xref:System.AggregateException> instances thrown by multiple tasks in a single <xref:System.AggregateException> instance, as the following example shows.  
 
  :::code language="csharp" source="~/samples/snippets/csharp/VS_Snippets_Misc/tpl_exceptions/cs/taskexceptions2.cs" id="Snippet13":::
+ :::code language="fsharp" source="~/samples/snippets/fsharp/VS_Snippets_Misc/tpl_exceptions/fs/taskexceptions2.fs" id="Snippet13":::
  :::code language="vb" source="~/samples/snippets/visualbasic/VS_Snippets_Misc/tpl_exceptions/vb/taskexceptions2.vb" id="Snippet13":::  
 
  ]]></format>
@@ -712,11 +715,13 @@
  Ordinarily, an exception handler that catches an <xref:System.AggregateException> exception uses a `foreach` loop (in C#) or `For Each` loop (in Visual Basic) to handle each exception in its <xref:System.AggregateException.InnerExceptions%2A> collection. Instead, the following example uses the <xref:System.AggregateException.Handle%2A> method to handle each exception, and only re-throws exceptions that are not `CustomException` instances.  
 
  :::code language="csharp" source="~/samples/snippets/csharp/VS_Snippets_Misc/tpl_exceptions/cs/handlemethod2.cs" id="Snippet16":::
+ :::code language="fsharp" source="~/samples/snippets/fsharp/VS_Snippets_Misc/tpl_exceptions/fs/handlemethod2.fs" id="Snippet16":::
  :::code language="vb" source="~/samples/snippets/visualbasic/VS_Snippets_Misc/tpl_exceptions/vb/handlemethod2.vb" id="Snippet16":::  
 
  The following is a more complete example that uses the <xref:System.AggregateException.Handle%2A> method to provide special handling for an <xref:System.UnauthorizedAccessException> when enumerating files.  
 
  :::code language="csharp" source="~/samples/snippets/csharp/VS_Snippets_Misc/tpl_exceptions/cs/taskexceptions.cs" id="Snippet12":::
+ :::code language="fsharp" source="~/samples/snippets/fsharp/VS_Snippets_Misc/tpl_exceptions/fs/taskexceptions.fs" id="Snippet12":::
  :::code language="vb" source="~/samples/snippets/visualbasic/VS_Snippets_Misc/tpl_exceptions/vb/taskexceptions.vb" id="Snippet12":::  
 
  ]]></format>