Linq OrderBy calculated property - linq

Question

I use expression builder to sort and filter table data. However, the query doesn't execute when there's a calculation in the property.
I read similar post here but couldn't find an answer!
e.g. if I try to sort the query below by "Due", it fails with the error below.
System.InvalidOperationException: The LINQ expression 'DbSet()
.Where(i => i.OrganisationId == __organisationId_0)
.OrderBy(i => (Nullable)(DateTime.Now - i.PaymentDueDate).TotalDays)' 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.
How do I cope this situation or am I doing anything wrong here?
thanks, much appreciated!
Method:
public async Task<PaginatedList<GetInvoiceListDto>> Handle(GetInvoiceListQuery request, CancellationToken cancellationToken)
{
var organisationId = _tenantService.GetOrganisationId();
return await _context.Invoices
.Include(i => i.InvoiceSaleItems)
.Where(w => w.OrganisationId == organisationId)
.Select(y => new GetInvoiceListDto
{
Status = y.PaymentDueDate < DateTime.Now ? "Overdue" : "Sent",
Due = (DateTime.Now - y.PaymentDueDate).TotalDays,
InvoiceDate = y.InvoiceDate,
InvoiceNumber = y.InvoiceNumber,
CustomerName = y.Customer.CustomerName,
AmountDue = y.InvoiceSaleItems.Sum(yx => yx.Amount) + y.InvoiceSaleItems.SelectMany(ss => ss.InvoiceSaleItemTaxes).Sum(sg => sg.Amount),
}).PaginatedListAsync(request.PageNumber, request.PageSize, request.SortColumn, request.SortOrder, request.q);
}
Extension:
public static Task<PaginatedList<TDestination>> PaginatedListAsync<TDestination>(this IQueryable<TDestination> queryable, int pageNumber, int pageSize, string sortColumn, string sortOrder, string filter)
=> PaginatedList<TDestination>.CreateAsync(queryable, pageNumber, pageSize, sortColumn, sortOrder, filter);
public static async Task<PaginatedList<T>> CreateAsync(IQueryable<T> source, int pageIndex, int pageSize, string sortColumn, string sortOrder, string filter)
{
var query = source;
// query = query.Filter<T>(filter); // commented for simplicity.
query = query.OrderBy<T>(sortColumn, sortOrder);
var count = query.Count(); // <= The error is thrown at this line.
var items = await Task.FromResult (query.Skip((pageIndex - 1) * pageSize).Take(pageSize).ToList());
return new PaginatedList<T>(items, count, pageIndex, pageSize);
}
public static IQueryable<T> OrderBy<T>(this IQueryable<T> query, string sortColumn, string direction)
{
var methodNameFirst = string.Format("OrderBy{0}", direction.ToLower() == "asc" ? "" : "descending");
var methodNameContinue = string.Format("ThenBy{0}", direction.ToLower() == "asc" ? "" : "descending");
ParameterExpression parameter = Expression.Parameter(query.ElementType, "p");
Expression result = query.Expression;
var methodName = methodNameFirst;
foreach (var fields in sortColumn.Split(','))
{
Expression memberAccess = null;
foreach (var property in fields.Split('.'))
{
if (string.IsNullOrEmpty(property.Trim()) == false)
{
var newProp = "";
if (property.IndexOf(" asc") == -1)
{
newProp = property.Trim();
}
else
{
newProp = property.Substring(0, property.IndexOf(" asc")).Trim();
}
try
{
memberAccess = MemberExpression.Property(memberAccess ?? (parameter as Expression), newProp);
}
catch (Exception e)
{
}
}
}
LambdaExpression orderByLambda = Expression.Lambda(memberAccess, parameter);
result = Expression.Call(
typeof(Queryable),
methodName,
new[] { query.ElementType, memberAccess.Type },
result,
Expression.Quote(orderByLambda));
methodName = methodNameContinue;
}
return query.Provider.CreateQuery<T>(result);
}

Answer 1

Instead of using (DateTime.Now - y.PaymentDueDate).TotalDays try to replace with something that EF Core can translate to the SQL:
return await _context.Invoices
.Where(w => w.OrganisationId == organisationId)
.Select(y => new GetInvoiceListDto
{
Status = y.PaymentDueDate < DateTime.Now ? "Overdue" : "Sent",
Due = EF.Functions.DateDiffDay(DateTime.Now, y.PaymentDueDate),
InvoiceDate = y.InvoiceDate,
InvoiceNumber = y.InvoiceNumber,
CustomerName = y.Customer.CustomerName,
AmountDue = y.InvoiceSaleItems.Sum(yx => yx.Amount) + y.InvoiceSaleItems.SelectMany(ss => ss.InvoiceSaleItemTaxes).Sum(sg => sg.Amount),
}).PaginatedListAsync(request.PageNumber, request.PageSize, request.SortColumn, request.SortOrder, request.q);
Note, that I have removed Include which is not needed if you have Select.