Convert to Lambda expression

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

Why would you want to convert it?

For complex queries like this one the query syntax you have used here is invariably clearer.

Answer 2

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()};