用linq排序組內

Question

我有一個對象列表。我想按日期排序，然後按TransParentType然後按TransType排序。然後我想通過TransParentType進行分組，並在每個組內放置一個特定項目（如果存在）在組的底部（撤銷：特定）。

樣本數據：

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 

預期排序的數據：

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 

我試圖做這樣的事情，但沒有成功。 GroupBy不維護我的排序數據。這就像我已經得到。不知道是否有一種方法，以具體項目移動到組的底部，或者如果我必須做手工......

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

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

Answer 1

好了，我沒有看到該組由的需要您的預期分類數據。

我會做

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(); 

編輯：

按照給定的新規格，我看到的東西（醜陋的），這樣的

 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

你在你的問題顯示輸出沒有按」 t組，完全是：

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

如果我嘗試你的代碼，我發現GroupBy確實保持順序，除了明顯地將它分成兩個單獨的組。

如果GroupBy確實打亂順序（雖然我不能看到），那麼你可以使用：

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

，這將給你一個IEnumerable<OrderedEnumerable<>>，這樣你就可以foreach通過每個塊，然後通過foreach那些按順序，等等。 （或者如果針對不同的linq源完成IQueryable<IOrderedQueryable<>>）。

Answer 3

我相信這樣的事情會工作：

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