Entity Framework OrderBy().Where() expression - entity-framework

Question

I've been using Entity Framework for a little while now with no issues, until i stumbled upon a curly one....well it is for me atleast anyway. I have searched the internet and cannot find anything related to this but i assume it is merely because i am asking the wrong question. So here goes...
query= query.OrderByDescending(u => u.DateCreated);
This is simple and works fine. However the table being queried is for workflow and there are 4 date columns, CreatedDate, EstimatedDate, RevisedDate and ActualDate. At the beginning of the workflow for this element the CreatedDate will and all the other date columns will be NULL. As the element progresses through workflow the subsequent dates will be filled.
So what i am trying to achieve is this, i don't want any grouping, i just want the date to be used for OrderBy() to be the last date in the workflow.
I can achieve this by adding another column to my table called FilterDate which is used solely for sorting and gets updated with the appropriate date based upon workflow, however this is adding another column to my table just because I can't come up with a smart method of achieving this.

Answer 1

It's not pretty, but this should be what you're looking for, assuming that ActualDate (if populated) is always >= RevisedDate >= EstimatedDate => CreatedDate:
query= query.OrderByDescending(u => u.ActualDate.HasValue
? u.ActualDate.Value
: u.RevisedDate.HasValue
? u.RevisedDate.Value
: u.EstimatedDate.HasValue
? u.EstimatedDate.Value
: u.CreatedDate);
This will order by whichever date is available preferencing the Actual over Revised over Estimated and defaulting to the Created.
This doesn't handle if it's possible that a RevisedDate could be after an ActualDate for instance. If the row had an RevisedDate of 2020-12-02 and an ActualDate of 2020-11-25, this query would be using the ActualDate for comparison, not the later RevisedDate.

Answer 2

If I understand your question properly then you don't need to add an extra column to your table.
You just need to add a [NotMapped] decorated property to your object, because that property won't be saved in the database.
[NotMapped]
public DateTime FilteringDate
{
get
{
if (ActualDate.HasValue) return (DateTime)ActualDate;
else if (RevisedDate.HasValue) return (DateTime)RevisedDate;
else if (EstimatedDate.HasValue) return (DateTime)EstimatedDate;
else return CreatedDate;
}
}
usage
query = query.OrderByDescending(u => u.FilteringDate);