LINQ Using Max() to select a single row

Question

I'm using LINQ on an IQueryable returned from NHibernate and I need to select the row with the maximum value(s) in a couple of fields.

I've simplified the bit that I'm sticking on. I need to select the one row from my table with the maximum value in one field.

var table = new Table { new Row(id: 1, status: 10), new Row(id: 2, status: 20) }  from u in table group u by 1 into g where u.Status == g.Max(u => u.Status) select u 

This is incorrect but I can't work out the right form.

BTW, what I'm actually trying to achieve is approximately this:

var clientAddress = this.repository.GetAll()     .GroupBy(a => a)     .SelectMany(             g =>             g.Where(                 a =>                 a.Reference == clientReference &&                  a.Status == ClientStatus.Live &&                  a.AddressReference == g.Max(x => x.AddressReference) &&                  a.StartDate == g.Max(x => x.StartDate)))     .SingleOrDefault(); 

I started with the above lambda but I've been using LINQPad to try and work out the syntax for selecting the Max().

UPDATE

Removing the GroupBy was key.

var all = this.repository.GetAll();  var address = all             .Where(                 a =>                 a.Reference == clientReference &&                  a.Status == ClientStatus.Live &&                  a.StartDate == all.Max(x => x.StartDate) &&                 a.AddressReference == all.Max(x => x.AddressReference))             .SingleOrDefault(); 

Answer 1

I don't see why you are grouping here.

Try this:

var maxValue = table.Max(x => x.Status) var result = table.First(x => x.Status == maxValue); 

An alternate approach that would iterate table only once would be this:

var result = table.OrderByDescending(x => x.Status).First(); 

This is helpful if table is an IEnumerable<T> that is not present in memory or that is calculated on the fly.

Answer 2

You can also do:

(from u in table orderby u.Status descending select u).Take(1);