I 've got a simple query but it throws, that it couldn't be translated

here is the function

    public async Task<Voucher> Get(Predicate<Voucher> predicate)
    {
        try
        {
           var voucher = await _promotionCoreContext.Vouchers.AsNoTracking().FirstOrDefaultAsync(i => predicate(i));
           return voucher;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex.Message);
        }
    }

usage is something like this:

repository.Get(c => c.Code == "abc");

but for a reason it can't translate the predicate, it compiles though.

---- System.InvalidOperationException : The LINQ expression 'DbSet() .Where(v => Invoke(__predicate_0, v) )' 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

Anyone know how I can fix this without making it client side with ToList()

CodePudding user response：

The IQueryable.FirstOrDefaultAsync takes an Expression<Func<TSource,bool>>, not a Func<TSource,bool>. The Enumerable extension methods can work with Func<TSource,bool>, but since that's basically a function pointer, EF can't translate it to SQL.