net10.0 
namespace System.Web
{
    [DefaultMember("Item")]
    public sealed class HttpFileCollection : NameObjectCollectionBase
    {
        [Obsolete("Retrieving Keys is not supported on .NET 6+. Please use the enumerator instead.")]
        public override KeysCollection! Keys { get; }
    }
}
.NET
8.09.010.0
Information specific to net10.0
Assembly

Microsoft.AspNetCore.SystemWebAdapters , Version=2.2.1.0, PublicKeyToken=adb9793829ddae60

Referencing

Your project needs a package reference to Microsoft.AspNetCore.SystemWebAdapters.

Package Microsoft.AspNetCore.SystemWebAdapters (2.2.1) net10.0
Obsolete Retrieving Keys is not supported on .NET 6+. Please use the enumerator instead.
Platform Restrictions

The property getter is supported on all platforms.

  • Built-in API
  • Package-provided API