IcedTasks 0.11.7

dotnet add package IcedTasks --version 0.11.7                
NuGet\Install-Package IcedTasks -Version 0.11.7                
This command is intended to be used within the Package Manager Console in Visual Studio, as it uses the NuGet module's version of Install-Package.
<PackageReference Include="IcedTasks" Version="0.11.7" />                
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add IcedTasks --version 0.11.7                
#r "nuget: IcedTasks, 0.11.7"                
#r directive can be used in F# Interactive and Polyglot Notebooks. Copy this into the interactive tool or source code of the script to reference the package.
// Install IcedTasks as a Cake Addin
#addin nuget:?package=IcedTasks&version=0.11.7

// Install IcedTasks as a Cake Tool
#tool nuget:?package=IcedTasks&version=0.11.7                


What is IcedTasks?

This library contains additional computation expressions for the task CE utilizing the Resumable Code introduced in F# 6.0.

  • ValueTask<'T> - This utilizes .NET's ValueTask (which is essentially a Discriminated Union of 'Value | Task<'Value>) for possibly better performance in synchronous scenarios. Similar to F#'s Task Expression

    • valueTask
    • valueTaskUnit
    • poolingValueTask
  • ColdTask<'T> - Alias for unit -> Task<'T>. Allows for lazy evaluation (also known as Cold) of the tasks, similar to F#'s Async being cold.

    • coldTask
  • CancellableTask<'T> - Alias for CancellationToken -> Task<'T>. Allows for lazy evaluation (also known as Cold) of the tasks, similar to F#'s Async being cold. Additionally, allows for flowing a CancellationToken through the computation, similar to F#'s Async cancellation support.

    • cancellableTask
    • cancellableBackgroundTask
  • CancellableValueTask<'T> - Alias for CancellationToken -> ValueTask<'T>. Allows for lazy evaluation (also known as Cold) of the tasks, similar to F#'s Async being cold. Additionally, allows for flowing a CancellationToken through the computation, similar to F#'s Async cancellation support.

    • cancellableValueTask
    • cancellablePoolingValueTask
  • ParallelAsync<'T> - Utilizes the applicative syntax to allow parallel execution of Async<'T> expressions. See this discussion as to why this is a separate computation expression.

    • parallelAsync
  • AsyncEx<'T> - Variation of F# async semantics described further below with examples.

    • asyncEx
    • This can also be accessed under IcedTasks.Polyfill.Async which will shadow the F# Async CE.
      • async
  • Task<'T> - Polyfill for fixes to F# Task CE. Can be accessed under IcedTasks.Polyfill.Task which will shadow the F# Task CE.

    • task
    • backgroundTask
  • Task - a CE for a Task that has no return value.

    • taskUnit
    • backgroundTaskUnit

Differences at a glance

Computation Expression<sup>1</sup> Library<sup>2</sup> TFM<sup>3</sup> Hot/Cold<sup>4</sup> Multiple Awaits <sup>5</sup> Multi-start<sup>6</sup> Tailcalls<sup>7</sup> CancellationToken propagation<sup>8</sup> Cancellation checks<sup>9</sup> Parallel when using and!<sup>10</sup> use IAsyncDisposable <sup>11</sup>
F# Async FSharp.Core netstandard2.0 Cold Multiple multiple tailcalls implicit implicit No No
F# AsyncEx IcedTasks netstandard2.0 Cold Multiple multiple tailcalls implicit implicit No Yes
F# ParallelAsync IcedTasks netstandard2.0 Cold Multiple multiple tailcalls implicit implicit Yes No
F# Task/C# Task FSharp.Core netstandard2.0 Hot Multiple once-start no tailcalls explicit explicit No Yes
F# ValueTask IcedTasks netstandard2.0 Hot Once once-start no tailcalls explicit explicit Yes Yes
F# ColdTask IcedTasks netstandard2.0 Cold Multiple multiple no tailcalls explicit explicit Yes Yes
F# CancellableTask IcedTasks netstandard2.0 Cold Multiple multiple no tailcalls implicit implicit Yes Yes
F# CancellableValueTask IcedTasks netstandard2.0 Cold Once multiple no tailcalls implicit implicit Yes Yes
  • <sup>1</sup> - Computation Expression
  • <sup>2</sup> - Which Nuget package do they come from
  • <sup>3</sup> - Which Target Framework Moniker these are available in
  • <sup>4</sup> - Hot refers to the asynchronous code block already been started and will eventually produce a value. Cold refers to the asynchronous code block that is not started and must be started explicitly by caller code. See F# Async Tutorial and Asynchronous C# and F# (II.): How do they differ? for more info.
  • <sup>5</sup> - ValueTask Awaiting patterns
  • <sup>6</sup> - Multi-start refers to being able to start the asynchronous code block again. See FAQ on Task Start for more info.
  • <sup>7</sup> - Allows use of let rec with the computation expression. See Tail call Recursion for more info.
  • <sup>8</sup> - CancellationToken is propagated to all types the support implicit CancellatationToken passing. Calling cancellableTask { ... } nested inside async { ... } (or any of those combinations) will use the CancellationToken from when the code was started.
  • <sup>9</sup> - Cancellation will be checked before binds and runs.
  • <sup>10</sup> - Allows parallel execution of the asynchronous code using the Applicative Syntax in computation expressions.
  • <sup>11</sup> - Allows use of IAsyncDisposable with the computation expression. See IAsyncDisposable for more info.

Why should I use this?


AsyncEx is similar to Async except in the following ways:

  1. Allows use for IAsyncDisposable

    open IcedTasks
    let fakeDisposable () = { new IAsyncDisposable with member __.DisposeAsync() = ValueTask.CompletedTask }
    let myAsyncEx = asyncEx {
        use _ = fakeDisposable ()
        return 42
  2. Allows let!/do! against Tasks/ValueTasks/any Awaitable

    open IcedTasks
    let myAsyncEx = asyncEx {
        let! _ = task { return 42 } // Task<T>
        let! _ = valueTask { return 42 } // ValueTask<T>
        let! _ = Task.Yield() // YieldAwaitable
        return 42
  3. When Tasks throw exceptions they will use the behavior described in Async.Await overload (esp. AwaitTask without throwing AggregateException

    let data = "lol"
    let inner = asyncEx {
            task {
                do! Task.Yield()
                raise (ArgumentException "foo")
                return data
            :> Task
    let outer = asyncEx {
            do! inner
            return ()
        | :? ArgumentException ->
            // Should be this exception and not AggregationException
            return ()
        | ex ->
            return raise (Exception("Should not throw this type of exception", ex))
  4. Use IAsyncEnumerable with for keyword. This example uses TaskSeq but you can use any IAsyncEnumerable<T>.

    open IcedTasks
    open FSharp.Control
    let myAsyncEx = asyncEx {
        let items = taskSeq {  // IAsyncEnumerable<T>
            yield 42
            do! Task.Delay(100)
            yield 1701
        let mutable sum = 0
        for i in items do
            sum <- sum + i
        return sum

For ValueTasks

open IcedTasks

let myValueTask = task {
    let! theAnswer = valueTask { return 42 }
    return theAnswer

For Cold & CancellableTasks

  • You want control over when your tasks are started
  • You want to be able to re-run these executable tasks
  • You don't want to pollute your methods/functions with extra CancellationToken parameters
  • You want the computation to handle checking cancellation before every bind.


Short example:

open IcedTasks

let coldTask_dont_start_immediately = task {
    let mutable someValue = null
    let fooColdTask = coldTask { someValue <- 42 }
    do! Async.Sleep(100)
    // ColdTasks will not execute until they are called, similar to how Async works
    Expect.equal someValue null ""
    // Calling fooColdTask will start to execute it
    do! fooColdTask ()
    Expect.equal someValue 42 ""

CancellableTask & CancellableValueTask

The examples show cancellableTask but cancellableValueTask can be swapped in.

Accessing the context's CancellationToken:

  1. Binding against CancellationToken -> Task<_>

    let writeJunkToFile = 
        let path = Path.GetTempFileName()
        cancellableTask {
            let junk = Array.zeroCreate bufferSize
            use file = File.Create(path)
            for i = 1 to manyIterations do
                // You can do! directly against a function with the signature of `CancellationToken -> Task<_>` to access the context's `CancellationToken`. This is slightly more performant.
                do! fun ct -> file.WriteAsync(junk, 0, junk.Length, ct)
  2. Binding against CancellableTask.getCancellationToken

    let writeJunkToFile = 
        let path = Path.GetTempFileName()
        cancellableTask {
            let junk = Array.zeroCreate bufferSize
            use file = File.Create(path)
            // You can bind against `CancellableTask.getCancellationToken` to get the current context's `CancellationToken`.
            let! ct = CancellableTask.getCancellationToken ()
            for i = 1 to manyIterations do
                do! file.WriteAsync(junk, 0, junk.Length, ct)

Short example:

let executeWriting = task {
    // CancellableTask is an alias for `CancellationToken -> Task<_>` so we'll need to pass in a `CancellationToken`.
    // For this example we'll use a `CancellationTokenSource` but if you were using something like ASP.NET, passing in `httpContext.RequestAborted` would be appropriate.
    use cts = new CancellationTokenSource()
    // call writeJunkToFile from our previous example
    do! writeJunkToFile cts.Token


  • When you want to execute multiple asyncs in parallel and wait for all of them to complete.

Short example:

open IcedTasks

let exampleHttpCall url = async {
    // Pretend we're executing an HttpClient call
    return 42

let getDataFromAFewSites = parallelAsync {
    let! result1 = exampleHttpCall "howManyPlantsDoIOwn"
    and! result2 = exampleHttpCall "whatsTheTemperature"
    and! result3 = exampleHttpCall "whereIsMyPhone"

    // Do something meaningful with results
    return ()


GitHub Actions
GitHub Actions
Build History


Package Stable Prerelease
IcedTasks NuGet Badge NuGet Badge


Make sure the following requirements are installed on your system:


Environment Variables

  • CONFIGURATION will set the configuration of the dotnet commands. If not set, it will default to Release.
    • CONFIGURATION=Debug ./ will result in -c additions to commands such as in dotnet build -c Debug
  • GITHUB_TOKEN will be used to upload release notes and Nuget packages to GitHub.
    • Be sure to set this before releasing


> build.cmd <optional buildtarget> // on windows
$ ./  <optional buildtarget>// on unix

The bin of your library should look similar to:

$ tree src/MyCoolNewLib/bin/
└── Debug
    └── net50
        ├── MyCoolNewLib.deps.json
        ├── MyCoolNewLib.dll
        ├── MyCoolNewLib.pdb
        └── MyCoolNewLib.xml

Build Targets

  • Clean - Cleans artifact and temp directories.
  • DotnetRestore - Runs dotnet restore on the solution file.
  • DotnetBuild - Runs dotnet build on the solution file.
  • DotnetTest - Runs dotnet test on the solution file.
  • GenerateCoverageReport - Code coverage is run during DotnetTest and this generates a report via ReportGenerator.
  • WatchTests - Runs dotnet watch with the test projects. Useful for rapid feedback loops.
  • GenerateAssemblyInfo - Generates AssemblyInfo for libraries.
  • DotnetPack - Runs dotnet pack. This includes running Source Link.
  • SourceLinkTest - Runs a Source Link test tool to verify Source Links were properly generated.
  • PublishToNuGet - Publishes the NuGet packages generated in DotnetPack to NuGet via paket push.
  • GitRelease - Creates a commit message with the Release Notes and a git tag via the version in the Release Notes.
  • GitHubRelease - Publishes a GitHub Release with the Release Notes and any NuGet packages.
  • FormatCode - Runs Fantomas on the solution file.
  • BuildDocs - Generates Documentation from docsSrc and the XML Documentation Comments from your libraries in src.
  • WatchDocs - Generates documentation and starts a webserver locally. It will rebuild and hot reload if it detects any changes made to docsSrc files, libraries in src, or the docsTool itself.
  • ReleaseDocs - Will stage, commit, and push docs generated in the BuildDocs target.
  • Release - Task that runs all release type tasks such as PublishToNuGet, GitRelease, ReleaseDocs, and GitHubRelease. Make sure to read Releasing to setup your environment correctly for releases.


git add .
git commit -m "Scaffold"
git remote add origin
git push -u origin master
  • Create your NuGeT API key

    paket config add-token "" 4003d786-cc37-4004-bfdf-c4f3e8ef9b3a
    • or set the environment variable NUGET_TOKEN to your key
  • Create a GitHub OAuth Token

    • You can then set the environment variable GITHUB_TOKEN to upload release notes and artifacts to github
    • Otherwise it will fallback to username/password
  • Then update the with an "Unreleased" section containing release notes for this version, in KeepAChangelog format.

NOTE: Its highly recommend to add a link to the Pull Request next to the release note that it affects. The reason for this is when the RELEASE target is run, it will add these new notes into the body of git commit. GitHub will notice the links and will update the Pull Request with what commit referenced it saying "added a commit that referenced this pull request". Since the build script automates the commit message, it will say "Bump Version to x.y.z". The benefit of this is when users goto a Pull Request, it will be clear when and which version those code changes released. Also when reading the CHANGELOG, if someone is curious about how or why those changes were made, they can easily discover the work and discussions.

Here's an example of adding an "Unreleased" section to a with a 0.1.0 section already released.

## [Unreleased]

### Added
- Does cool stuff!

### Fixed
- Fixes that silly oversight

## [0.1.0] - 2017-03-17
First release

### Added
- This release already has lots of features

  • You can then use the Release target, specifying the version number either in the RELEASE_VERSION environment variable, or else as a parameter after the target name. This will:
    • update, moving changes from the Unreleased section into a new 0.2.0 section
      • if there were any prerelease versions of 0.2.0 in the changelog, it will also collect their changes into the final 0.2.0 entry
    • make a commit bumping the version: Bump version to 0.2.0 and adds the new changelog section to the commit's body
    • publish the package to NuGet
    • push a git tag
    • create a GitHub release for that git tag

macOS/Linux Parameter:

./ Release 0.2.0

macOS/Linux Environment Variable:

RELEASE_VERSION=0.2.0 ./ Release
Product Compatible and additional computed target framework versions.
.NET net5.0 was computed.  net5.0-windows was computed.  net6.0 is compatible.  net6.0-android was computed.  net6.0-ios was computed.  net6.0-maccatalyst was computed.  net6.0-macos was computed.  net6.0-tvos was computed.  net6.0-windows was computed.  net7.0 was computed.  net7.0-android was computed.  net7.0-ios was computed.  net7.0-maccatalyst was computed.  net7.0-macos was computed.  net7.0-tvos was computed.  net7.0-windows was computed.  net8.0 was computed.  net8.0-android was computed.  net8.0-browser was computed.  net8.0-ios was computed.  net8.0-maccatalyst was computed.  net8.0-macos was computed.  net8.0-tvos was computed.  net8.0-windows was computed. 
.NET Core netcoreapp2.0 was computed.  netcoreapp2.1 was computed.  netcoreapp2.2 was computed.  netcoreapp3.0 was computed.  netcoreapp3.1 was computed. 
.NET Standard netstandard2.0 is compatible.  netstandard2.1 is compatible. 
.NET Framework net461 was computed.  net462 was computed.  net463 was computed.  net47 was computed.  net471 was computed.  net472 was computed.  net48 was computed.  net481 was computed. 
MonoAndroid monoandroid was computed. 
MonoMac monomac was computed. 
MonoTouch monotouch was computed. 
Tizen tizen40 was computed.  tizen60 was computed. 
Xamarin.iOS xamarinios was computed. 
Xamarin.Mac xamarinmac was computed. 
Xamarin.TVOS xamarintvos was computed. 
Xamarin.WatchOS xamarinwatchos was computed. 
Compatible target framework(s)
Included target framework(s) (in package)
Learn more about Target Frameworks and .NET Standard.

NuGet packages (3)

Showing the top 3 NuGet packages that depend on IcedTasks:

Package Downloads

FsToolkit.ErrorHandling is an extensive utility library based around the F# Result type, enabling consistent and powerful error handling.


This is the core library for the Migrondi CLI, you can use this library to run the same functionality of Migrondi as part of your source code or to write an abstraction for different kind of tools.


Package Description

GitHub repositories

This package is not used by any popular GitHub repositories.

Version Downloads Last updated
0.11.7 284 7/11/2024
0.11.6 600 5/8/2024
0.11.5 2,937 4/22/2024
0.11.4 866 4/6/2024
0.11.3 481 2/7/2024
0.11.2 89 2/7/2024
0.11.0 546 1/31/2024
0.10.2 322 1/29/2024
0.10.0 13,345 11/22/2023
0.9.2 7,483 11/9/2023
0.9.1 98 11/8/2023
0.9.0 130 11/6/2023
0.8.5 725 10/29/2023
0.8.5-beta001 98 10/28/2023
0.8.4 119 10/28/2023
0.8.3 114 10/27/2023
0.8.2 342 10/23/2023
0.8.2-beta003 86 10/23/2023
0.8.0 2,342 7/18/2023
0.7.1 177 7/8/2023
0.7.0 5,131 7/4/2023
0.6.0 181 6/30/2023
0.6.0-beta001 122 6/30/2023
0.5.4 5,555 4/3/2023
0.5.4-beta004 122 4/3/2023
0.5.3 11,049 2/22/2023
0.5.1 3,045 12/17/2022
0.5.0 527 12/9/2022
0.5.0-beta001 118 12/9/2022
0.4.0 370 12/2/2022
0.3.2 326 12/1/2022
0.3.2-beta002 125 12/1/2022
0.3.2-beta001 109 12/1/2022
0.3.1 334 11/27/2022
0.3.1-beta002 124 11/27/2022
0.3.1-beta001 123 11/27/2022
0.3.0 1,312 11/8/2022
0.3.0-beta007 126 11/8/2022
0.3.0-beta006 130 11/8/2022
0.3.0-beta005 87 11/8/2022
0.3.0-beta004 91 11/8/2022
0.3.0-beta001 86 11/7/2022
0.2.0 38,059 3/23/2022
0.1.1 424 3/7/2022
0.1.0 526 3/6/2022
0.1.0-beta004 145 3/6/2022
0.1.0-beta003 151 3/6/2022
0.1.0-beta002 157 3/6/2022
0.1.0-beta001 154 3/6/2022

## [0.11.7] - 2024-07-10


### Fixed
- [Fix Disposes not happening on cancellation]( - Credits @TheAngryByrd