将List <t>转换为嵌套的Dictionary <string，dictionary <string，=“”t =“”>

Question

我遇到了一个基本问题。我需要将平面列表转换为类型为Dictionary<string,Dictionary<string,Dictionary<string,Dictionary<string,string>>>>

的嵌套字典

我几乎已经完成了，除了我需要对多个属性进行分组这一事实，并且我使用了匿名类型。这是一个例子：

List<ApprovalAction> Gen()
{
    return new List<ApprovalAction>
    {
        new ApprovalAction { Name = "SendMailToApprover", Step="New", ApprovalRequestType = "Homeworking", ParameterName = "to", ParameterValue="Approver" },
        new ApprovalAction { Name = "SendMailToApprover", Step="New", ApprovalRequestType = "Homeworking", ParameterName="subject", ParameterValue = "Aproval Request" },
        new ApprovalAction { Name = "SendMailToApprover", Step="New", ApprovalRequestType = "Homeworking", ParameterName="body", ParameterValue = "I would like an approval request"},
        new ApprovalAction { Name = "SendMailToApprover", Step="New", ApprovalRequestType = "Absence", ParameterName="to" , ParameterValue="Approver" },
        new ApprovalAction { Name = "SendMailToApprover", Step="New", ApprovalRequestType = "Absence", ParameterName="subject", ParameterValue = "Aproval Request" },
        new ApprovalAction { Name = "SendMailToApprover", Step="New", ApprovalRequestType = "Absence", ParameterName="body", ParameterValue = "I would like an approval request"}
    };
}


    var actions = Gen();
    var dico = actions
                .GroupBy(x => x.ApprovalRequestType)
                .ToDictionary(
                    gdc => gdc.Key,
                    gdc => gdc.GroupBy(a => a.Step)
                            .ToDictionary(dd => dd.Key, dd => dd.GroupBy(x => new { x.Name, x.Step, x.ApprovalRequestType }, (key, group) => new
                            {
                                Key = key.Name,
                                Result = group.ToDictionary(k => k.ParameterName, v => v.ParameterValue)
                            })));

这是Linqpad的输出：

您知道我可以替换哪些代码来避免IEnumerable吗？

谢谢！

Answer 1

IEnumerable<>来自最终GroupBy。如果您知道最里面的组只包含一个项目，请使用Single()。否则使用First()：

var dico = actions
    .GroupBy(x => x.ApprovalRequestType)
    .ToDictionary(
        gdc => gdc.Key,
        gdc => gdc.GroupBy(a => a.Step)
            .ToDictionary(dd => dd.Key, dd => dd.GroupBy(x => new { x.Name, x.Step, x.ApprovalRequestType }, (key, group) => new {
                Key = key.Name,
                Result = group.ToDictionary(k => k.ParameterName, v => v.ParameterValue)
            }).First()
        )
    );

上面的查询结果如下所示：