Data in Linq query not in join is not in output to json only those that are related in 2 classes are showing up

Question

The basis of this question is from this question:

Combine 2 classes with adding data and 1 table has a colllection list of the other table and wanting to use linq to dis

Answer 1

I think the linked question was not answered correctly.

Looks like all you need is a simple Group Join:

var query = 
    from d in reportData
    join r in reportDefinition on d.ReportGroupId equals r.ReportGroupId into items
    select new
    {
        d.ReportGroupName,
        items = items.ToList(),
        d.ReportGroupId
    };