[API Proposal]: IsEmpty Linq extension property

[ladeak]

Background and motivation

Add IsEmpty Linq extension property as discussed here: https://build.microsoft.com/en-US/sessions/BRK114?source=sessions (t=28:40)

API Proposal

namespace System.Linq;
public static partial class Enumerable
{
    extension<T>(IEnumerable<T> source)
    {
        public bool IsEmpty { get; }
    }
}

API Usage

List<int> mycollection = new();
Console.WriteLine(mycollection.IsEmpty);

Alternative Designs (EDITED)

namespace System.Linq;
public static partial class Collections
{
    extension<T>(ICollection<T> source)
    {
        public bool IsEmpty { get; }
    }
}

Risks

Cluttering the API.

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[stephentoub]

Such a member could end up doing an unknown amount of work, as in the case of a non-collection IEnumerable<T>, it would need to enumerate to see if there's at least one element, just like Any() does. Properties are supposed to be cheap. I don't see us adding this, especially as it'd just be a synonym for !Any().

[ladeak]

Such a member could end up doing an unknown amount of work, as in the case of a non-collection IEnumerable<T>, it would need to enumerate to see if there's at least one element

This concern makes sense; I would modify (adding an alternative design) the proposal to be an extension method to ICollection<T>. In this case the implementation becomes trivial shorthand for Count == 0, which I wouldn't see much value to be provided by the class libraries.

I will keep the proposal open for another day to see if anyone else sees value, and closing after.