我们为集合做的时候如何使用GroupBy？

Question

我有以下代码：

private IDictionary<Guid, JobStatistic> GetAgentsStatistics(IList<Guid> agentIds, DateTime startTime, DateTime endTime)
    {
        ...
        IDictionary<Guid, JobStatistic> jobStatistics = reportData.GroupBy(item => item.AgentId)
                                      .ToDictionary(items => items.Key, items => items.ToJobsStatistic());

        // Some agents might not have any records in specified period of time
        var missingAgents = agentIds.Except(jobStatistics.Keys);
        missingAgents.ForEach(agentId => jobStatistics.Add(agentId, new JobStatistic()));

        return jobStatistics;
    }

但现在我更改了我的DataContract（报告数据），我需要使用item.AgentIds而不是item.AgentId。如何更改代码以使用一组元素执行相同的操作？

Answer 1

我可能会使用不同形式的LINQ。我觉得这样的事情可行：

var jobStatisticsResult = from data in reportData
                    from agentId in data.AgentIds
                    group data by agentId
                    into grp
                    select new { AgentId = grp.Key, Items = grp.ToList() };

var jobStatistics = jobStatisticsResult.ToDictionary(x => x.AgentId, x => x.Items.ToJobsStatistic());