Widely-used DistinctBy workaround causes other errors

[lonix1]

Originally asked on SO without resolution.

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A query:

List<Guid> productCodes = GetProductCodes();  
var products = await _context
  .Products
  .Where(x => productCodes.Contains(x.ProductCode))
  .GroupBy(x => x.ProductCode).Select(x => x.First())    // workaround for `DistinctBy`
  .Select(x => new { SupplierId = x.Supplier.Id, WarehouseId = x.Warehouse.Id, x.ProductCode, x.Price, ... })
  .ToListAsync();

Result:

InvalidOperationException: The LINQ expression 'ProjectionBindingExpression: 0' could not
be translated. Either rewrite the query in a form that can be translated, or switch to
client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable',
'ToList', or 'ToListAsync'.

I use the GroupBy/Select-First workaround instead of DistinctBy which is currently unsupported.

I assume from the error message that the projection in .Select() is the problem; when I remove that the query works. I could perform the projection afterwards, but then I'd be fetching large quantities of data for nothing.

Is there a way to workaround this issue until there is DistinctBy support?

EF Core version: 7.0.16
Database provider: Npsql
Target framework: 7.0
Operating system: linux
IDE: vscode 1.90.2

[roji]

7.0 is out of support, please upgrade to 8.0 and confirm that the issue is still present there.

[lonix1]

I'll do that and reopen if necessary, thank you.