Question

我有一个对象列表。我想按日期排序，然后按TransParentType排序，然后按TransType排序。然后我想按TransParentType进行分组，并在每个组中放置一个特定项目（如果存在）放在组的底部（撤销：具体）。

示例数据：

Date          TransParentType   TransType

2015/05/20    Purchase      investment
2015/05/20    Redemption    withdrawal: b
2015/05/20    Redemption    zz
2015/05/20    Redemption    withdrawal: a
2015/05/20    Redemption    withdrawal: specific
2015/05/20    Redemption    withdrawal: c   
2015/05/14    Purchase      investment

预期的排序数据：

Date          TransParentType   TransType

2015/05/14    Purchase      investment
2015/05/20    Purchase      investment
2015/05/20    Redemption    withdrawal: a
2015/05/20    Redemption    withdrawal: b
2015/05/20    Redemption    withdrawal: c
2015/05/20    Redemption    withdrawal: specific
2015/05/20    Redemption    zz

我正在尝试做这样的事情，没有太大的成功。 GroupBy不维护我的排序数据。这是我已经得到的。不确定是否有办法将特定项目移动到组的底部，或者我是否必须手动执行...

results = results.OrderBy(r => r.Date).ThenBy(r=>r.TransParentType)
                             .ThenBy(r => r.TransType).ToList();

var grouped = results.GroupBy(g => g.TransParentType)...

Answer 1

好吧，我从预期的排序数据中看不到该组的需要。

我愿意

results = results.OrderBy(r => r.Date)
                 .ThenBy(r=>r.TransParentType)
                 //just add an order criterion, checking if TransType == the value that you want at the end
                 //as order by a boolean returns false results first, this will put "widthdrawal: specific" at the end
                 //this will only make a difference for the elements starting with "withdrawal:"
                 .ThenBy(r => r.TransType == "widthdrawal: specific")
                 //finally, order TransType for all elements
                 .ThenBy(r => r.TransType)
                 .ToList();

编辑：

根据新规范，我会看到像（<丑闻）那样的东西

        results = results
                     //order by date
                    .OrderBy(m => m.Date)
                    //order by transParentType
                    .ThenBy(m => m.TransParentType)
                     //order by the beginning of TransType (the part which may contain "withdrawal:"
                    .ThenBy(m => m.TransType.Substring(0, Math.Min(11, m.TransType.Length)))
                    .ThenBy(m => m.TransType == "withdrawal: specific")
                    .ThenBy(m => m.TransType);

Answer 2

我相信这样的事情会起作用：

results = results
    .OrderBy(r => r.Date)
    .ThenBy(r => r.TransParentType)
    .ThenBy(r => r.TransType == "withdrawal: specific" ? 1 : 0)
    .ThenBy(r => r.TransType).ToList();

Answer 3

您在问题中显示的输出根本不会分组，只是：

results.OrderBy(r => r.TransParentType).ThenBy(r => r.Date).ThenBy(r => r.TransType == "withdrawal: specific").ThenBy(r => r.TransType);

如果我尝试使用您的代码，我发现GroupBy确实维护了顺序，除非显然将它拆分为两个单独的组。

如果GroupBy确实令订单失望（虽然我看不清楚），那么你可以使用：

var groupedResults = results.GroupBy(r => r.Trans‎ParentType).Select(grp => grp.OrderBy(r => r.Date).ThenBy(r => r.TransType == "withdrawal: specific").ThenBy(r => r.TransType));

这将为您提供IEnumerable<OrderedEnumerable<>>，因此您可以foreach遍历每个块，然后foreach再次按顺序排列，依此类推。（如果针对不同的linq源完成，则为IQueryable<IOrderedQueryable<>>。）

使用linq在组内排序

3 个答案: