FsToolkit.ErrorHandling.IcedTasks 4.15.1

dotnet add package FsToolkit.ErrorHandling.IcedTasks --version 4.15.1
NuGet\Install-Package FsToolkit.ErrorHandling.IcedTasks -Version 4.15.1
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="FsToolkit.ErrorHandling.IcedTasks" Version="4.15.1" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add FsToolkit.ErrorHandling.IcedTasks --version 4.15.1
#r "nuget: FsToolkit.ErrorHandling.IcedTasks, 4.15.1"
#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 FsToolkit.ErrorHandling.IcedTasks as a Cake Addin
#addin nuget:?package=FsToolkit.ErrorHandling.IcedTasks&version=4.15.1

// Install FsToolkit.ErrorHandling.IcedTasks as a Cake Tool
#tool nuget:?package=FsToolkit.ErrorHandling.IcedTasks&version=4.15.1


FsToolkit.ErrorHandling is a utility library to work with the Result type in F#, and allows you to do clear, simple and powerful error handling.

The library provides utility functions like map, bind, apply, traverse, sequence as well as computation expressions and infix operators to work with Result<'a, 'b>, Result<'a option, 'b>, Async<Result<'a, 'b>>, Async<Result<'a option, 'b>>, and Result<'a, 'b list>.

It was inspired by Chessie and Cvdm.ErrorHandling (the latter has now been merged into FsToolkit.ErrorHandling).

FsToolkit.ErrorHandling targets .NET Standard 2.0 and .NET Framework 4.6.1 and supports Fable.


The documentation is available here.

Further material


GitHub Actions
GitHub Actions
Build History


Package name Release Prelease
FsToolkit.ErrorHandling NuGet NuGet
FsToolkit.ErrorHandling.TaskResult NuGet NuGet
FsToolkit.ErrorHandling.JobResult NuGet NuGet
FsToolkit.ErrorHandling.AsyncSeq NuGet NuGet
FsToolkit.ErrorHandling.IcedTasks NuGet NuGet

Developing locally


This repository has a devcontainer setup for VSCode. For more infomation see:

Local Setup


To test fable builds locally you will need:

  • Node
    • v18.0.0 or Higher
    • Not required but recommend that you use NVM to easily manage multiple versions of Node
  • Python
    • v3.10.0 or higher
    • Required for Fable-Python
> build.cmd <optional buildtarget> // on windows
$ ./build.sh  <optional buildtarget>// on unix

Without specifying a build target, the default target is DotnetPack, which will run tests for all projects on dotnet and then pack the projects into nuget packages. For additional notable targets see below.

Build Targets
  • Clean - Will clean all projects bin and obj folders
  • DotnetTest - Will run tests for dotnet projects
  • NpmTest - Will run tests for fable-javascript projects
  • PythonTest - Will run tests for fable-python projects
  • RunTests - Will run tests for dotnet, fable-javascript and fable-python projects
  • FormatCode - Will run fantomas to format the codebase

This is not an exhausting list. Additional targets can be found in the ./build/build.fs file.

A motivating example

This example of composing a login flow shows one example of how this library can aid in clear, simple, and powerful error handling, using just a computation expression and a few helper functions. (The library has many more helper functions and computation expressions as well as infix operators; see the documentation for details.)

// Given the following functions:
//   tryGetUser: string -> Async<User option>
//   isPwdValid: string -> User -> bool
//   authorize: User -> Async<Result<unit, AuthError>>
//   createAuthToken: User -> Result<AuthToken, TokenError>

type LoginError = InvalidUser | InvalidPwd | Unauthorized of AuthError | TokenErr of TokenError

let login (username: string) (password: string) : Async<Result<AuthToken, LoginError>> =
  asyncResult {
    // requireSome unwraps a Some value or gives the specified error if None
    let! user = username |> tryGetUser |> AsyncResult.requireSome InvalidUser

    // requireTrue gives the specified error if false
    do! user |> isPwdValid password |> Result.requireTrue InvalidPwd

    // Error value is wrapped/transformed (Unauthorized has signature AuthError -> LoginError)
    do! user |> authorize |> AsyncResult.mapError Unauthorized

    // Same as above, but synchronous, so we use the built-in mapError
    return! user |> createAuthToken |> Result.mapError TokenErr


<a href="https://www.ajira.tech"><img src="./Ajira-logo.png" alt="Ajira Technologies, India" width="200" /></a>

Product Compatible and additional computed target framework versions.
.NET net5.0 was computed.  net5.0-windows was computed.  net6.0 was computed.  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 netcoreapp3.0 was computed.  netcoreapp3.1 was computed. 
.NET Standard netstandard2.1 is compatible. 
MonoAndroid monoandroid was computed. 
MonoMac monomac was computed. 
MonoTouch monotouch was computed. 
Tizen 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)
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Learn more about Target Frameworks and .NET Standard.

NuGet packages

This package is not used by any NuGet packages.

GitHub repositories

This package is not used by any popular GitHub repositories.

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