Question

I have the following expression

        var q = from c in D1                  join dp in                     (from e in E1                      group e by e.ID into g                      select new { ID = g.Key, Cnt = g.Count() })                 on c.ID                 equals dp.ID                  into dpp from v in dpp.DefaultIfEmpty()                  select new { c.ID, Cnt= v.Cnt ?? 0 }; 

How can i convert this to Lambda expression?

Answer 1

Here’s one way to go. This kind-of matches the above.

var subquery = E1   .GroupBy(e => e.Id)   .Select(g => new { ID = g.Key, Cnt = g.Count()});   //.ToList();  var q = D1   .GroupJoin(     subquery,     c => c.ID,     dp => dp.ID,     (c, g) => new {ID = c.ID, Cnt=g.Any() ? g.First().Cnt : 0 }   ) 

After refactoring, I came up with this:

var q = D1   .GroupJoin(     E1,     d => d.ID,     e => e.ID,     (d, g) => new {ID = d.ID, Cnt = g.Count()}   ); 

For comparision, the query comprehension form is:

var q = from d in D1   join e in E1 on d.ID equals e.ID into g   select new {ID = d.ID, Cnt = g.Count()};