Editing Multiple dispatch (section)

==== C# ====
[[C Sharp (programming language)|C#]] introduced support for dynamic multimethods in version 4<ref>{{cite web
 |url=https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/types/using-type-dynamic
 |title=Using type dynamic (C# Programming Guide)
 |access-date=2020-05-14
}}</ref> (April 2010) using the 'dynamic' keyword. The following example demonstrates multimethods.  Like many other statically-typed languages, C# also supports static method overloading.<ref>{{cite web
 |url=https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/language-specification/basic-concepts#signatures-and-overloading
 |title=Basic concepts
 |access-date=2020-05-14
}}</ref> Microsoft expects that developers will choose static typing over dynamic typing in most scenarios.<ref>{{cite web
 |url=https://docs.microsoft.com/en-us/archive/msdn-magazine/2011/february/msdn-magazine-dynamic-net-understanding-the-dynamic-keyword-in-csharp-4
 |title=Dynamic .NET - Understanding the Dynamic Keyword in C# 4
 |date=10 August 2015
 |access-date=2020-05-14
}}</ref>  The 'dynamic' keyword supports interoperability with COM objects and dynamically-typed .NET languages.

[[File:Csharp ColliderLibrary.svg]]

The example below uses features introduced in C# 9 and C# 10.

<syntaxhighlight lang="c#">
using static ColliderLibrary;

Console.WriteLine(Collide(new Asteroid(101), new Spaceship(300)));
Console.WriteLine(Collide(new Asteroid(10), new Spaceship(10)));
Console.WriteLine(Collide(new Spaceship(101), new Spaceship(10)));

string Collide(SpaceObject x, SpaceObject y) =>
    x.Size > 100 && y.Size > 100
        ? "Big boom!"
        : CollideWith(x as dynamic, y as dynamic); // Dynamic dispatch to CollideWith method

class ColliderLibrary
{
    public static string CollideWith(Asteroid x, Asteroid y) => "a/a";
    public static string CollideWith(Asteroid x, Spaceship y) => "a/s";
    public static string CollideWith(Spaceship x, Asteroid y) => "s/a";
    public static string CollideWith(Spaceship x, Spaceship y) => "s/s";
}

abstract record SpaceObject(int Size);
record Asteroid(int Size) : SpaceObject(Size);
record Spaceship(int Size) : SpaceObject(Size);
</syntaxhighlight>

Output:
<syntaxhighlight lang="output">
Big boom!
a/s
s/s
</syntaxhighlight>