LINQ to SQL lambda exp. OrderBy, Case When,Dynamic Where

Question

I'm using LINQ to SQL and LINQ dynamic where and order by.

I want to convert the code below(ASP) to C#.net.

    function getTestimonialList(statusCd)
     sWhere = ""
     if statusCd <> "" then
    sWhere = " where status='" & statusCd & "'"
     end if
     sqlStr="select * from testimonial" & sWhere & " order by case when status = 'P' then 1 when status = 'A' then 2 else 3 end, dateadded desc"
     set rs=getResult(sqlStr)
     set getTestimonialList=rs
end function

Here is my query :

var TestimonialList = from p in MainModelDB.Testimonials
                                  where String.IsNullOrEmpty(statusCd)?"1=1":p.status== statusCd
                              orderby p.status == 'P' ? 1 : (p.status == 'A' ? 2 : 3)
                              orderby p.DateAdded descending
                              select p;

the above example doesn't work! , any idea if its possible? any other way to do it?

Thanks

Answer 1

Instead of trying to use a query expression, I suggest you use the Where, OrderBy and ThenByDescending methods directly. For example:

IQueryable<Testimonial> testimonials = MainModelDB.Testimonials;
if (!string.IsNullOrEmpty(statusCd))
{
    testimonials = testimonials.Where(t => t.status == statusCd);
}
var ordered = testimonials.OrderBy(t => t.status == 'P' ? 
                                           1 : (t.status == 'A' ? 2 : 3))
                          .ThenByDescending(t => t.DateAdded);

Note the use of ThenByDescending instead of OrderByDescending - your original query used two "primary" orderings which is almost never what you want.

I'm not entirely sure that the OrderBy clause will work, but it's worth a try. If it doesn't work, please say what happens instead of just saying "it doesn't work".