dustincampbell/csharpdemos

Various public C# demos

csharpdemos's Issues

How ImmutableArray and ImmutableList work differently

I'm taking the liberty of simplifying the code of your conference to point out an error I have at home.

Console.WriteLine(CheckNotes([]));
Console.WriteLine(CheckNotes([3.99m]));
Console.WriteLine(CheckNotes([1.0m, 2.0m, 3.0m, 4.0m]));


Note CheckNotes(ImmutableArray<Note> notes) => notes switch
{
    [] => 2.0m,
    [var note] => note,
    [..var all] => all.Average(),
};

Here everything works correctly, but if I change ImmutableArray to ImmutableList I get an exception

Note CheckNotes(ImmutableList<Note> notes) => notes switch
{
    [] => 2.0m,
    [var note] => note,
    [..var all] => all.Average(),
};

and the exception

/***/RiderProjects/Tests/CSharp12Conference/CSharp12Conference/Program.cs(23,6): error CS1503: Argument 1: cannot convert from 'System.Range' to 'int' [/***/RiderProjects/Tests/CSharp12Conference/CSharp12Conference/CSharp12Conference.csproj]
/***/RiderProjects/Tests/CSharp12Conference/CSharp12Conference/Program.cs(23,20): error CS1929: 'decimal' does not contain a definition for 'Average' and the best extension method overload 'Enumerable.Average(IEnumerable<decimal>)' requires a receiver of type 'System.Collections.Generic.IEnumerable<decimal>' [/***/RiderProjects/Tests/CSharp12Conference/CSharp12Conference/CSharp12Conference.csproj]

The build failed. Fix the build errors and run again.

Thank you in advance for any clarification on this behavior.