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System.Threading.Tasks.Task F# snippets (#8870)
* Task F# snippets * fix complication errors
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‎snippets/fsharp/System.Threading.Tasks/Task/.ctor/Run11.fs‎

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module Run11
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// <Snippet11>
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open System.Threading
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open System.Threading.Tasks
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let showThreadInfo s =
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printfn $"%s{s} thread ID: {Thread.CurrentThread.ManagedThreadId}"
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showThreadInfo "Application"
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let t = Task.Run(fun () -> showThreadInfo "Task")
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t.Wait()
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// The example displays the following output:
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// Application thread ID: 1
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// Task thread ID: 3
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// </Snippet11>

‎snippets/fsharp/System.Threading.Tasks/Task/.ctor/Run28.fs‎

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module Run28
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// <Snippet28>
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open System
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open System.Collections.Generic
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open System.Threading
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open System.Threading.Tasks
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let source = new CancellationTokenSource()
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let token = source.Token
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let mutable completedIterations = 0
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let tasks =
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[| for _ = 0 to 19 do
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Task.Run(
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(fun () ->
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let mutable iterations = 0
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for _ = 1 to 2000000 do
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token.ThrowIfCancellationRequested()
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iterations <- iterations + 1
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Interlocked.Increment &completedIterations |> ignore
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if completedIterations >= 10 then
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source.Cancel()
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iterations),
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token
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) |]
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printfn "Waiting for the first 10 tasks to complete...\n"
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try
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tasks |> Seq.cast |> Array.ofSeq |> Task.WaitAll
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with :? AggregateException ->
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printfn "Status of tasks:\n"
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printfn "%10s %20s %14s" "Task Id" "Status" "Iterations"
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for t in tasks do
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if t.Status <> TaskStatus.Canceled then
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t.Result.ToString "N0"
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else
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"n/a"
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|> printfn "%10i %20O %14s" t.Id t.Status
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// The example displays output like the following:
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// Status of tasks:
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//
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// Task Id Status Iterations
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// 1 RanToCompletion 2,000,000
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// 2 RanToCompletion 2,000,000
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// 3 RanToCompletion 2,000,000
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// 4 RanToCompletion 2,000,000
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// 5 RanToCompletion 2,000,000
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// 6 RanToCompletion 2,000,000
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// 7 RanToCompletion 2,000,000
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// 8 RanToCompletion 2,000,000
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// 9 RanToCompletion 2,000,000
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// 10 RanToCompletion 1,658,326
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// 11 RanToCompletion 1,988,506
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// 12 RanToCompletion 2,000,000
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// 13 RanToCompletion 1,942,246
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// 14 RanToCompletion 950,108
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// 15 RanToCompletion 1,837,832
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// 16 RanToCompletion 1,687,182
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// 17 RanToCompletion 194,548
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// 18 Canceled Not Started
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// 19 Canceled Not Started
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// 20 Canceled Not Started
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// </Snippet28>

‎snippets/fsharp/System.Threading.Tasks/Task/.ctor/Run7.fs‎

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module Run7
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// <Snippet7>
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open System
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open System.Collections.Generic
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open System.Threading
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open System.Threading.Tasks
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let source = new CancellationTokenSource()
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let token = source.Token
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let mutable completedIterations = 0
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let tasks =
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[| for _ = 0 to 19 do
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Task.Run(
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(fun () ->
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let mutable iterations = 0
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for _ = 1 to 2000000 do
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token.ThrowIfCancellationRequested()
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iterations <- iterations + 1
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Interlocked.Increment &completedIterations |> ignore
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if completedIterations >= 10 then
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source.Cancel()
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iterations),
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token
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)
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|]
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printfn "Waiting for the first 10 tasks to complete...\n"
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try
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tasks |> Seq.cast |> Array.ofSeq |> Task.WaitAll
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with :? AggregateException ->
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printfn "Status of tasks:\n"
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printfn "%10s %20s %14s" "Task Id" "Status" "Iterations"
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for t in tasks do
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if t.Status <> TaskStatus.Canceled then
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t.Result.ToString "N0"
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else
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"n/a"
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|> printfn "%10i %20O %14s" t.Id t.Status
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// The example displays output like the following:
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// Waiting for the first 10 tasks to complete...
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// Status of tasks:
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//
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// Task Id Status Iterations
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// 1 RanToCompletion 2,000,000
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// 2 RanToCompletion 2,000,000
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// 3 RanToCompletion 2,000,000
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// 4 RanToCompletion 2,000,000
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// 5 RanToCompletion 2,000,000
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// 6 RanToCompletion 2,000,000
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// 7 RanToCompletion 2,000,000
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// 8 RanToCompletion 2,000,000
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// 9 RanToCompletion 2,000,000
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// 10 Canceled n/a
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// 11 Canceled n/a
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// 12 Canceled n/a
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// 13 Canceled n/a
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// 14 Canceled n/a
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// 15 Canceled n/a
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// 16 RanToCompletion 2,000,000
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// 17 Canceled n/a
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// 18 Canceled n/a
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// 19 Canceled n/a
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// 20 Canceled n/a
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// </Snippet7>

‎snippets/fsharp/System.Threading.Tasks/Task/.ctor/ctor1.fs‎

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module ctor1
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// <Snippet1>
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open System.Collections.Concurrent
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open System.IO
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open System.Threading.Tasks
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let main =
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task {
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let list = ConcurrentBag<string>()
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let dirNames = [ "."; ".." ]
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let tasks = ResizeArray()
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for dirName in dirNames do
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let t =
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new Task(fun () ->
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for path in Directory.GetFiles dirName do
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list.Add path)
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tasks.Add t
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t.Start()
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do! tasks.ToArray() |> Task.WhenAll
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for t in tasks do
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printfn $"Task {t.Id} Status: {t.Status}"
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printfn $"Number of files read: {list.Count}"
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}
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// The example displays output like the following:
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// Task 1 Status: RanToCompletion
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// Task 2 Status: RanToCompletion
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// Number of files read: 23
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// </Snippet1>

‎snippets/fsharp/System.Threading.Tasks/Task/.ctor/fs.fsproj‎

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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<OutputType>Exe</OutputType>
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<TargetFramework>net7.0</TargetFramework>
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</PropertyGroup>
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<ItemGroup>
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<Compile Include="ctor1.fs" />
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<Compile Include="run2.fs" />
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<Compile Include="run4.fs" />
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<Compile Include="startnew3.fs" />
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<Compile Include="Run11.fs" />
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<Compile Include="run6.fs" />
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<Compile Include="run41.fs" />
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<Compile Include="run31.fs" />
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<Compile Include="Run7.fs" />
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<Compile Include="Run28.fs" />
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</ItemGroup>
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</Project>

‎snippets/fsharp/System.Threading.Tasks/Task/.ctor/run2.fs‎

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module run2
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// Example for Task.Run(Action) method.
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// <Snippet1>
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open System.Collections.Concurrent
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open System.IO
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open System.Threading.Tasks
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let list = ConcurrentBag<string>()
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let dirNames = [ "."; ".." ]
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let tasks = ResizeArray()
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for dirName in dirNames do
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let t =
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Task.Run(fun () ->
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for path in Directory.GetFiles dirName do
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list.Add path)
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tasks.Add t
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tasks.ToArray() |> Task.WaitAll
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for t in tasks do
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printfn $"Task {t.Id} Status: {t.Status}"
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printfn $"Number of files read: {list.Count}"
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// The example displays output like the following:
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// Task 1 Status: RanToCompletion
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// Task 2 Status: RanToCompletion
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// Number of files read: 23
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// </Snippet1>

‎snippets/fsharp/System.Threading.Tasks/Task/.ctor/run31.fs‎

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module run31
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// <Snippet2>
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open System
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open System.IO
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open System.Text.RegularExpressions
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open System.Threading.Tasks
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let pattern = @"\p{P}*\s+"
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let titles = [| "Sister Carrie"; "The Financier" |]
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let tasks =
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Array.map (fun title ->
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Task.Run(fun () ->
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// Create filename from title.
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let fn = title + ".txt"
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if File.Exists fn then
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use sr = new StreamReader(fn)
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let input = sr.ReadToEndAsync().Result
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Regex.Matches(input, pattern).Count
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else
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0)) titles
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tasks |> Seq.cast |> Array.ofSeq |> Task.WaitAll
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printfn "Word Counts:\n"
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for i = 0 to tasks.Length - 1 do
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printfn $"%s{titles.[i]}: %10d{tasks.[i].Result} words"
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// The example displays the following output:
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// Sister Carrie: 159,374 words
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// The Financier: 196,362 words
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// </Snippet2>

‎snippets/fsharp/System.Threading.Tasks/Task/.ctor/run4.fs‎

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module run4
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// Illustrates the Task.Run(Action, CancellationToken) overload.
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// <Snippet4>
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open System
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open System.IO
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open System.Threading
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open System.Threading.Tasks
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let main =
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task {
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use tokenSource = new CancellationTokenSource()
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let token = tokenSource.Token
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let files = ResizeArray()
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let t =
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new Task(
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(fun () ->
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let dir = @"C:\Windows\System32\"
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let obj = obj ()
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if Directory.Exists dir then
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Parallel.ForEach(
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Directory.GetFiles dir,
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fun f ->
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if token.IsCancellationRequested then
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token.ThrowIfCancellationRequested()
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let fi = FileInfo f
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lock obj (fun () -> files.Add(fi.Name, fi.DirectoryName, fi.Length, fi.LastWriteTimeUtc))
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)
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|> ignore),
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token
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)
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t.Start()
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tokenSource.Cancel()
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try
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do! t
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printfn $"Retrieved information for {files.Count} files."
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with :? AggregateException as e ->
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printfn "Exception messages:"
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for ie in e.InnerExceptions do
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printfn $" {ie.GetType().Name}: {ie.Message}"
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printfn $"Task status: {t.Status}"
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}
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main.Wait()
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// The example displays the following output:
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// Exception messages:
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// TaskCanceledException: A task was canceled.
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//
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// Task status: Canceled
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// </Snippet4>

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