什么是C＃Linq等效于VB.Net Linq Group Join和Into关键字？

Question

I am trying to rewrite an old vb.net app in C#. I have come across this linq code that I need to convert:

 (From wn In dtx.WebQueryGroupNames Group Join _
                    wqg In dtx.WebQueryGroups On wn.QueryGroupNameKey Equals wqg.QueryGroupNameKey _
                    Into Group _
                    From p In Group.DefaultIfEmpty() _
                    Select wn _
                    Where Not (From x In dtx.WebQueryGroups Where x.QueryKey = queryKey Select x.QueryGroupNameKey).Contains(wn.QueryGroupNameKey)).Distinct.ToList

What I have so far is:

 (from wn in dtx.WebQueryGroupNames Group join  
        wqg in dtx.WebQueryGroups on wn.QueryGroupNameKey equals wqg.QueryGroupNameKey 
        Into Group 
        from p in Group.DefaultIfEmpty() 
        select wn 
        where !(from x in dtx.WebQueryGroups where x.QueryKey = queryKey select x.QueryGroupNameKey).Contains(wn.QueryGroupNameKey)).Distinct(); 

I can't seem to find any information on the Group and Into keywords as it translates to C#. I think I am missing a key point that makes this query make sense.

Answer 1

I believe Group Join translates into a plan join with an into clause. Try this

 (from wn in dtx.WebQueryGroupNames join  
        wqg in dtx.WebQueryGroups on wn.QueryGroupNameKey equals wqg.QueryGroupNameKey 
        into g
        from p in g.DefaultIfEmpty() 
        select wn 
        where !(from x in dtx.WebQueryGroups where x.QueryKey = queryKey select x.QueryGroupNameKey).Contains(wn.QueryGroupNameKey)).Distinct();

See http://msdn.microsoft.com/en-us/library/bb397905.aspx

Answer 2

The term you're looking for is Group By .

var queryLastNames =
    from student in students
    group student by student.LastName into newGroup
    orderby newGroup.Key
    select newGroup;