The LINQ expression could not be translated in CROSS APPLY

Question

I am trying to get the result of CROSS APPLY between a dbSet and a list of object.

    public class BudgetRate : BaseEntity
    {
        public string CurrencyCode { get; set; }
        public DateTime ValueDate { get; set; }
        public decimal RateValue { get; set; }
        public virtual Currency Currency { get; set; }
    }

    public class TestClass
    {
        public DateTime ExchangeDate { get; set; }
        public string ExchangeCurrencyCode { get; set; }
    }

I have tried the following:

List<TestClass> testClasses = new();
// Logic to fill the list
var query = from a in _dbContext.BudgetRate
            from b in testClasses
                 .Where(b => a.ValueDate <= b.ExchangeDate && a.CurrencyCode == b.ExchangeCurrencyCode).ToList()
                 .OrderByDescending(b => a.ValueDate).Take(1)
            select new
            {
                Key = a.ValueDate.ToString() + ',' + a.CurrencyCode,
                a.RateValue,
            };

However I am getting the following exception:

The LINQ expression 'a => __testClasses_0
    .Where(b => a.ValueDate <= b.ExchangeDate && a.CurrencyCode == b.ExchangeCurrencyCode)
    .AsQueryable()
    .OrderByDescending(b => a.ValueDate)
    .Take(1)' 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'