FSharp.Control.TaskSeq

FSharp.Control.TaskSeq provides a taskSeq computation expression for IAsyncEnumerable<'T>, along with a comprehensive TaskSeq module.

An task sequence is an asynchronous sequence in which individual elements are awaited: the next element is not necessarily available immediately. Under the hood each taskSeq { ... } is an IAsyncEnumerable<'T> — the .NET standard interface used by C# await foreach, Entity Framework Core, gRPC streaming, and many other libraries in the ecosystem.

Quick Start

Add the NuGet package FSharp.Control.TaskSeq to your project and open the namespace:

// #r "nuget: FSharp.Control.TaskSeq"

open FSharp.Control

A TaskSeq<'T> can be created with the taskSeq { ... } computation expression:

let oneThenTwo = taskSeq {
    yield 1
    do! Task.Delay 1000   // non-blocking sleep
    yield 2
}

When iterated, the sequence above yields 1 immediately and 2 after one second. Consumers must await each step.

Use await foreach in C#, or any TaskSeq consumer in F#:

// Iterate with a for loop inside a task { ... }
task {
    for item in oneThenTwo do
        printfn "Got %d" item
} |> Task.Run |> ignore

// Or use TaskSeq.iter
do! oneThenTwo |> TaskSeq.iter (printfn "Got %d")

Topics

• Generating sequences — taskSeq { }, init, unfold, ofArray, …
• Transforming sequences — map, filter, choose, collect, …
• Consuming sequences — iter, fold, find, toArray, sum, …
• Combining sequences — append, zip, take, skip, chunkBySize, …
• Advanced operations — groupBy, mapFold, distinct, partition, …

Comparison with FSharp.Control.AsyncSeq

FSharp.Control.AsyncSeq is the predecessor library, oriented towards Async<'T>. Both libraries implement IAsyncEnumerable<'T> so they are interoperable. The main differences are:

Related links

• NuGet package
• GitHub repository
• Release notes
• API reference