System.InvalidOperationException：无法使用带有 PostgreSQL 的 EF Core 翻译 LINQ 表达式

Question

I want to check if a list contains any item from another list using EF Core with Npsql provider. Then I want to get the exact item that was matched in my Dto.

My code is the following (note: Reports.Models is List<string> and so is request.Models as well. The request is consumer filter/search):

var x = await _dbContext.Reports
            .Where(x => x.Models.Any(i => request.Models.Contains(i)))
            .Select(x => new ReportDto
            {
                // Model = x.Identifiers.First(i => request.Identifiers.Contains(i)) // this also fails.
                Model = request.Models.First(i => request.Models.Any(y => y == i)), // fails on this line
            })
            .ToListAsync(cancellationToken);

I tried both ways using Any and Contains , neither work. They both return the same error which says:

System.InvalidOperationException: The LINQ expression 'i => __request_Models_0.Contains(i)' 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'. See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.

But I don't understand why? The error never changes, even in my case when I use Any , it still complains about Contains .

Answer 1

You are effectively trying to push your request.Models to the database Server for it to evaluate if any of its datasets are in it. That won't work.

You need to request the Models from the database first and compare them locally OR transform your request.Models into a set of IDs that the database can compare against.