Nested grouping with Linq? - asp.net

Question

I am trying to create a "simple" timesheet application that is almost doing what I need it to do, I'm not sure it's the most efficient way of doing this, so please give me feedback if you have better ideas... I got help here at SO before (See Group items with Linq and display in table in MVC view where you can also see the database schema). Now I just need to be able to group at one more nested level.
What I get now is a sort of table layout looking sort of like this:
Project Task 1 2 3 (dates with hours in the cells)
ProjA Analysis 8 8 8
ProjB Analysis 8 7 8
(Etc)
Here's the property in the viewmodel that I use to populate the table(s):
public IEnumerable<IGrouping<Project, TimeSegment>> TimeSegmentsByProject
{
get
{
var projectGroups = from timeSegment in ts.TimeSegments
group timeSegment by timeSegment.Project
into projectGroup
select projectGroup;
return projectGroups.ToList();
}
}
And here's the code in the View:
<table>
<tr>
<th>
Projekt
</th>
<th>
Aktivitet
</th>
<th>
Timmar
</th>
</tr>
<% foreach (var item in Model.TimeSegmentsByProject)
{ %>
<tr>
<td>
<%:item.Key.Name %>
</td>
<td>
<table>
<% foreach (var i in item)
{ %>
<tr>
<td>
<%: i.Task.Name %>
</td>
</tr>
<% } %>
</table>
</td>
<td>
<table>
<% foreach (var i in item)
{ %>
<tr>
<% for (int index = 0; index < 30; index++)
{%>
<td width="20px">
<%if (i.Date.Substring(8) == index.ToString())
{ %>
<%: i.Hours %>
<% } %>
</td>
<% } %>
</tr>
<% } %>
</table>
</td>
</tr>
<% } %>
</table>
Now, the problem is that this works fine, but even though Project is grouped and only appears once for each project, task is repeated with a new row for the same task name. I want each task only once, just like for Project. But the linq group expressions and all that has already got me so confused so I have no idea how to get this done. I'm in a bit over my head here, I thought a timesheet application would'nt be such a hard thing (at least a basic one). But I'm fairly close to something that would do, if I could just get this task grouping to work so I don't get it repeated.
Any advice for how to change my code to do this would be appreciated! (And if you think I'm doing it wrong, please tell me how)

Answer 1

Here's a stab at it.
var projectGroups =
from timeSegment in ts.TimeSegments
group timeSegment by new //start off by grouping two properties
{
ProjectName = timeSegment.Project.Name,
TaskName = timeSegment.Task.Name
} into g
select new
{
Key = g.Key,
Values = //and finish off by turning each group into another query.
(
from ts in g
group ts by ts.Date.Substring(8)) into g2
select new {
indexValue = g2.Key,
Hours = g2.Sum(ts2 => ts2.Hours)
}
).ToList()
};
Now, just because I used anonymous types here, doesn't mean you need to. You can declare actual classes and use them to project into. Just be careful with the class that serves as the grouping key (it has ProjectName and TaskName) as you don't want to use reference equality...