Convert.ToDateTime not working

Hi, With the following table:

CREATE TABLE public."Values"
(
    "Guid" bigint NOT NULL,
    "RawValue" text COLLATE pg_catalog."default",
    CONSTRAINT "Values_pkey" PRIMARY KEY ("Guid")
)

The following sample:

    public class EFCoreTestContext : DbContext
    {
        public DbSet<Value> Values { get; set; }

        public static readonly ILoggerFactory DebugLoggerFactory = LoggerFactory.Create(builder => { builder.AddFilter((category, level) => category == DbLoggerCategory.Database.Command.Name && level == LogLevel.Information).AddConsole(); });

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) => optionsBuilder
            .UseLoggerFactory(DebugLoggerFactory)
            .UseNpgsql("Host=localhost;Database=EFCoreTest;Username=test;Password=test");

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder
                .Entity<Value>(eb =>
                {
                    eb.ToTable("Values");
                    eb.HasKey(e => e.Guid);
                });
        }
    }

    public class Value
    {
        public long Guid { get; set; }

        public string RawValue { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            using (var db = new EFCoreTestContext())
            {
                var r = (from e in db.Values
                         select new
                         {
                             Date = Convert.ToDateTime(e.RawValue)
                         })
                         .OrderBy(e => e.Date)
                         .ToList();
            }

            Console.ReadKey();
        }
    }

I’m getting this error:

System.InvalidOperationException: The LINQ expression ‘DbSet<Value> .OrderBy(v => Convert.ToDateTime(v.RawValue))’ 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 either AsEnumerable(), AsAsyncEnumerable(), ToList(), or ToListAsync(). See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.

I was expecting this kind of query translated:

SELECT v."Guid", cast (v."RawValue" as timestamp with time zone) AS "Date"
FROM "Values" AS v
ORDER BY v."RawValue"

The values stored on the table in my case are something like this when they are DateTimes: “2020-01-21T14:33:29-03:00” I searched for some cast method like the EF.Functions.ILike method but had no luck.

Thanks in advance,

[smitpatel]

We had discussions about translating ToString method on object which would be whatever string representation of the value in database is.

[ajcvickers]

@roji I think we said that we would generate simple casts in the database, but would not try to be specific about how the conversions worked. However, I’m not sure either.