Gapotchenko.FX.Linq 2022.2.7

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dotnet add package Gapotchenko.FX.Linq --version 2022.2.7                
NuGet\Install-Package Gapotchenko.FX.Linq -Version 2022.2.7                
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="Gapotchenko.FX.Linq" Version="2022.2.7" />                
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add Gapotchenko.FX.Linq --version 2022.2.7                
#r "nuget: Gapotchenko.FX.Linq, 2022.2.7"                
#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 Gapotchenko.FX.Linq as a Cake Addin
#addin nuget:?package=Gapotchenko.FX.Linq&version=2022.2.7

// Install Gapotchenko.FX.Linq as a Cake Tool
#tool nuget:?package=Gapotchenko.FX.Linq&version=2022.2.7                


The module provides primitives for functional processing of data sequences.


Memoization is a pillar of functional data processing. You already met it quite often albeit in somewhat masked forms.

Gapotchenko.FX.Linq module provides the Memoize() extension method for IEnumerable<T> types. You can use it like this:

using Gapotchenko.FX.Linq;

var files = Directory.EnumerateFiles(".", "*.txt").Select(Path.GetFileName).Memoize();

Console.WriteLine("A text file with an upper case letter is present: {0}", files.Any(x => x.Any(char.IsUpper)));
Console.WriteLine("A text file with a name longer than 12 letters is present: {0}", files.Any(x => x.Length > 12));

Memoize() caches the already retrieved elements of a sequence, and does it lazily.

.NET developers often use ToList() and ToArray() methods for the very same purpose. But those methods are eager, as they retrieve all elements of a sequence in one shot. This often leads to suboptimal performance of an otherwise sound functional algorithm.

Memoize() solves that. This is the method you are going to use the most for LINQ caching.


The second most popular primitive provided by Gapotchenko.FX.Linq module is ScalarOrDefault() method. It is similar to SingleOrDefault() from conventional .NET but with one big difference: it does not throw an exception when sequence contains multiple elements.

SingleOrDefault() Semantics

using System.Linq;

new string[0].SingleOrDefault(); // returns null
new[] { "A" }.SingleOrDefault(); // returns "A"
new[] { "A", "B" }.SingleOrDefault(); // throws an exception 😞

ScalarOrDefault() Semantics

using Gapotchenko.FX.Linq;

new string[0].ScalarOrDefault(); // returns null
new[] { "A" }.ScalarOrDefault(); // returns "A"
new[] { "A", "B" }.ScalarOrDefault(); // returns null 👍

In practice, ScalarOrDefault() semantics is a big win as it allows to safely determine whether a given query converges to a scalar result.


Returns distinct elements from a sequence by using the default equality comparer on the keys extracted by a specified selector function.

The method is similar to Distinct() method provided by the stock System.Linq namespace, but allows to specify a selector function in order to differentiate the elements by a specific criteria.

Let's take a look at example:

using Gapotchenko.FX.Linq;

var source = new[]
    new { FirstName = "Alex", LastName = "Cooper" },
    new { FirstName = "John", LastName = "Walker" },
    new { FirstName = "Alex", LastName = "The Great" },
    new { FirstName = "Jeremy", LastName = "Doer" }

var query = source.DistinctBy(x => x.FirstName);

foreach (var i in query)

The code produces the following output:

{ FirstName = Alex, LastName = Cooper }
{ FirstName = John, LastName = Walker }
{ FirstName = Jeremy, LastName = Doer }


Returns a minimum/maximum value in a sequence according to a specified key selector function.

Let's take a look at example:

using Gapotchenko.FX.Linq;

var source = new[]
    new { FirstName = "Alex", LastName = "Cooper", Age = 45 },
    new { FirstName = "John", LastName = "Walker", Age = 17 },
    new { FirstName = "Alex", LastName = "The Great", Age = 1500 },
    new { FirstName = "Jeremy", LastName = "Doer", Age = 29 }

Console.WriteLine("The oldest person: {0}", source.MaxBy(x => x.Age));
Console.WriteLine("The youngest person: {0}", source.MinBy(x => x.Age));

The code produces the following output:

The oldest person: { FirstName = Alex, LastName = The Great, Age = 1500 }
The youngest person: { FirstName = John, LastName = Walker, Age = 17 }


These methods augment the semantics of conventional Min and Max methods, allowing to return the default value when the input sequence is empty. Conventional Min and Max methods just throw an exception in that case.

Other Modules

Let's continue with a look at some other modules provided by Gapotchenko.FX:

Or look at the full list of modules.

Product Compatible and additional computed target framework versions.
.NET net5.0 is compatible.  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 is compatible.  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 is compatible.  netcoreapp2.1 is compatible.  netcoreapp2.2 was computed.  netcoreapp3.0 is compatible.  netcoreapp3.1 was computed. 
.NET Standard netstandard2.0 is compatible.  netstandard2.1 is compatible. 
.NET Framework net46 is compatible.  net461 was computed.  net462 was computed.  net463 was computed.  net47 was computed.  net471 is compatible.  net472 is compatible.  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 (6)

Showing the top 5 NuGet packages that depend on Gapotchenko.FX.Linq:

Package Downloads

The module provides data structures and primitives for collections.


The module provides primitives for LINQ expressions.


Represents the Core profile of Gapotchenko.FX.


The module provides primitives and operations for geometry math.


The module provides the math operations for combinatorics.

GitHub repositories

This package is not used by any popular GitHub repositories.

Version Downloads Last updated
2022.2.7 2,079 5/1/2022
2022.2.5 1,861 5/1/2022
2022.1.4 1,934 4/6/2022
2021.2.21 1,990 1/21/2022
2021.2.20 1,929 1/17/2022
2021.1.5 1,018 7/6/2021
2020.2.2-beta 514 11/21/2020
2020.1.15 854 11/5/2020
2020.1.9-beta 504 7/14/2020
2020.1.8-beta 499 7/14/2020
2020.1.7-beta 538 7/14/2020
2020.1.1-beta 607 2/11/2020
2019.3.7 891 11/4/2019
2019.2.20 880 8/13/2019
2019.1.151 978 3/30/2019