Question

I have a datatable which contains a load of dates. I wanted to group these by date and give each row a count.

I have managed to do this by dong the following:

 IEnumerable query = from row in stats.AsEnumerable()
                     group row by row.Field<string>("date") into grp
                     select new { Date = grp.Key, Count = grp.Count(t => t["date"] != null) };

(where “stats” is the datatable)

I can see from debugging that this brings back the values all grouped as I need, but now I need to loop them and get each date and count.

My problem is I don’t know how to retrieve the values!

I have a foreach loop

foreach (var rw  in query)
{
   string date = rw.Date; // <---- this is my problem?
}

I don’t know what type my Ienumerable is to be able to reference the values in it!

So my question is how can I retrieve each date and count for each row by doing similar to the above?

I hope this makes sense!

Answer 1

This link on my blog should help you
http://www.matlus.com/linq-group-by-finding-duplicates/

Essentially your type is an anonymous type so you can’t reference it as a type but you can access the properties like you’re trying to do.

I think I see your issue. If you’re trying to return it from a method, you should define a type and reuturn it like shown below:

public IEnumerable<MyType> GetQuery()
{

  var query = from row in stats.AsEnumerable()
                    group row by row.Field<string>("date") into grp
                    select new { Date = grp.Key, Count = grp.Count(t => t["date"] != null) }; 

  foreach (var rw  in query)
  {
     yield return new MyType(rw.Date, rw.Count);
  }
}

declare your “query” variable using “var” as shown above.