Question

This is the query I am trying to do.

var commentActivity = project.ProjectDoc
        .Select(c => c.Comment.Select(i => i.UserID))
        .Distinct()
        .Count();

What I want is the number of comments from distinct users on a specific project, but ANY ProjectDoc. This query “works” the result is just wrong. The model is like this, generically sketched.

 Project
      ProjectDoc
           Comment

Update: I had to go one level deeper, based on the answer below I tried a few things that didn’t work so I though I would post this as a reference. Note the two SelectMany methods.

 var replyActivity = project.ProjectDoc
      .SelectMany(c => c.Comment.SelectMany(r => r.CommentReply.Select(u => u.UserID)))
      .Distinct()
      .Count();

Answer 1

Use SelectMany instead of Select

project.ProjectDoc
        .SelectMany(c => c.Comment.Select(i => i.UserID))
        .Distinct()
        .Count()