Blazor Server vs WASM - different output on `enumerable is ICollection<int>`

[tesar-tech]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Blazor app and this code:

List<int> list = [1,2,3];
IEnumerable<int> enumerable =list.Take(2);
bool isCollection = enumerable is ICollection<int>;

Console.WriteLine($"is ICollection: {isCollection} "); //true on server, false on wasm

Expected Behavior

The result should be the same on Blazor Servers and Blazor Wasm.

Steps To Reproduce

Clone this bug report repo (simple blazor app), run the app and visit:

• http://localhost:5031/
  • It will output isCollection as true
  • The exact code/page: https://github.com/tesar-tech/blazor_wasm_vs_server_bug/blob/master/blazor_wasm_vs_server_bug/Components/Pages/Home.razor
• http://localhost:5031/wasmhome
  • It will output false (it will briefly have true because of pre-rendering, but that's not the point)
  • The exact code/page: https://github.com/tesar-tech/blazor_wasm_vs_server_bug/blob/master/blazor_wasm_vs_server_bug.Client/WasmHome.razor

Exceptions (if any)

No response

.NET Version

9.0.100 (but was also on 8)

Anything else?

No response

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing
See info in area-owners.md if you want to be subscribed.

[dotnet-policy-service]

Tagging subscribers to this area: @mangod9
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[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-collections
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[pavelsavara]

It boils down to System.Linq.Enumerable+<TakeIterator> vs System.Linq.Enumerable+IListSkipTakeIterator<int>
which is because WASM uses code size optimized implementation and server uses speed optimized implementation.

I think that the public API doesn't claim that you could cast it to ICollection<int>.

I also believe this is by design since dotnet/corefx#31025

cc @stephentoub