score:0

Accepted answer
var query = (from wl in worklog
            join td in taskdefinition on wl.taskdefinitionid equals td.id
            join tg in taskgroup on td.taskgroupid equals tg.id
            where wl.employeeid == { 0} && wl.status == 5 
                && wl.starttime >= { 1} && wl.endtime < { 2}
            select new
            {
                project = tg.project,
                starttime = wl.starttime,
                endtime = wl.endtime
            })
            .groupby(o => o.project)
            .select(g => new
            {
                project = g.key,
                hours = g.sum(o => (o.endtime - o.starttime).minutes) / 60
            });

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